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Urbanization is a major contributor to the loss of biodiversity. Its rapid progress is mostly at the expense of natural ecosystems and the species inhabiting them. While some species can adjust quickly and thrive in cities, many others cannot. To support biodiversity conservation and guide management decisions in urban areas, it is important to find robust methods to estimate the urban affinity of species (i.e. their tendency to live in urban areas) and understand how it is associated with their traits. Since previous studies mainly relied on discrete classifications of species' urban affinity, often involving inconsistent assessments or variable parameters, their results were difficult to compare. To address this issue, we developed and evaluated a set of continuous indices that quantify species' urban affinity based on publicly available occurrence data. We investigated the extent to which a species' position along the urban affinity gradient depends on the chosen index and how this choice affects inferences about the relationship between urban affinity and a set of morphological, sensory and functional traits. While these indices are applicable to a wide range of taxonomic groups, we examined their performance using a global set of 356 bat species. As bats vary in sensitivity to anthropogenic disturbances, they provide an interesting case study. We found that different types of indices resulted in different rankings of species on the urban affinity spectrum, but this had little effect on the association of traits with urban affinity. Our results suggest that bat species predisposed to urban life are characterized by low echolocation call frequencies, relatively long call durations, small body size and flexibility in the selection of the roost type. We conclude that simple indices are appropriate and practical, and propose to apply them to more taxa to improve our understanding of how urbanization favours or filters species with particular traits.
Insect migration redistributes enormous quantities of biomass, nutrients and species globally. A subset of insect migrants perform extreme long-distance journeys, requiring specialized morphological, physiological and behavioral adaptations. The migratory globe skimmer dragonfly (Pantala flavescens) is hypothesized to migrate from India across the Indian Ocean to East Africa in the autumn, with a subsequent generation thought to return to India from East Africa the following spring. Using an energetic flight model and wind trajectory analysis, we evaluate the dynamics of this proposed transoceanic migration, which is considered to be the longest regular non-stop migratory flight when accounting for body size. The energetic flight model suggests that a mixed strategy of gliding and active flapping would allow a globe skimmer to stay airborne for up to 230–286 h, assuming that the metabolic rate of gliding flight is close to that of resting. If engaged in continuous active flapping flight only, the flight time is severely reduced to ∼4 h. Relying only on self-powered flight (combining active flapping and gliding), a globe skimmer could cross the Indian Ocean, but the migration would have to occur where the ocean crossing is shortest, at an exceptionally fast gliding speed and with little headwind. Consequently, we deem this scenario unlikely and suggest that wind assistance is essential for the crossing. The wind trajectory analysis reveals intra- and inter-seasonal differences in availability of favorable tailwinds, with only 15.2% of simulated migration trajectories successfully reaching land in autumn but 40.9% in spring, taking on average 127 and 55 h respectively. Thus, there is a pronounced requirement on dragonflies to be able to select favorable winds, especially in autumn. In conclusion, a multi-generational, migratory circuit of the Indian Ocean by the globe skimmer is shown to be achievable, provided that advanced adaptations in physiological endurance, behavior and wind selection ability are present. Given that migration over the Indian Ocean would be heavily dependent on the assistance of favorable winds, occurring during a relatively narrow time window, the proposed flyway is potentially susceptible to disruption, if wind system patterns were to be affected by climatic change.
Abstract
While chemical communication has been investigated intensively in vertebrates and insects, relatively little is known about the sensory world of spiders despite the fact that chemical cues play a key role in natural and sexual selection in this group. In insects, olfaction is performed with wall–pore and gustation with tip‐pore sensilla. Since spiders possess tip‐pore sensilla only, it is unclear how they accomplish olfaction. We scrutinized the ultrastructure of the trichoid tip‐pore sensilla of the orb weaving spider Argiope bruennichi—a common Palearctic species the males of which are known to be attracted by female sex pheromone. We also investigated the congener Argiope blanda. We examined whether the tip‐pore sensilla differ in ultrastructure depending on sex and their position on the tarsi of walking legs of which only the distal parts are in contact with the substrate. We hypothesized as yet undetected differences in ultrastructure that suggest gustatory versus olfactory functions. All tarsal tip‐pore sensilla of both species exhibit characters typical of contact‐chemoreceptors, such as (a) the presence of a pore at the tip of the sensillum shaft, (b) 2–22 uniciliated chemoreceptive cells with elongated and unbranched dendrites reaching up to the tip‐pore, (c) two integrated mechanoreceptive cells with short dendrites and large tubular bodies attached to the sensillum shaft's base, and (d) a socket structure with suspension fibres that render the sensillum shaft flexible. The newly found third mechanoreceptive cell attached to the proximal end of the peridendritic shaft cylinder by a small tubular body was likely overlooked in previous studies. The organization of tarsal tip‐pore sensilla did not differ depending on the position on the tarsus nor between the sexes. As no wall‐pore sensilla were detected, we discuss the probability that a single type of sensillum performs both gustation and olfaction in spiders.
Shallow aquatic environments are characterized by strong environmental variability. For ectotherms, temperature is the main driver of metabolic activity, thus also shaping performance. Ingestion rates in mysids are fast responses, influenced by metabolic and behavioral activity. We examined ingestion rates of the mysid Neomysis integer, collected in the Baltic Sea, after one-week exposure to different constant and fluctuating temperature regimes (5, 10, 15, 20°C and 9 ± 5, 14 ± 5°C, respectively). To investigate possible differences between sexes, thermal performance curves (TPCs) were established for female and male mysids based on ingestion rates measured at constant temperatures. TPCs of ingestion rates at constant temperatures differed between sexes, with female mysids showing a higher total ingestion rate as well as a higher thermal optimum compared to male mysids. Females showed reduced ingestion rates when exposed to fluctuating temperatures around their thermal optimum, whereas ingestion of male mysids was not reduced when exposed to fluctuating temperatures. The observed sex-specific differences might be related to potentially higher lipid and energy demands of the females. We suggest future studies should investigate males and females to improve our understanding about impacts of environmental variability on natural populations.
Introduction: At the cellular level, acute temperature changes alter ionic conductances, ion channel kinetics, and the activity of entire neuronal circuits. This can result in severe consequences for neural function, animal behavior and survival. In poikilothermic animals, and particularly in aquatic species whose core temperature equals the surrounding water temperature, neurons experience rather rapid and wide-ranging temperature fluctuations. Recent work on pattern generating neural circuits in the crustacean stomatogastric nervous system have demonstrated that neuronal circuits can exhibit an intrinsic robustness to temperature fluctuations. However, considering the increased warming of the oceans and recurring heatwaves due to climate change, the question arises whether this intrinsic robustness can acclimate to changing environmental conditions, and whether it differs between species and ocean habitats.
Methods: We address these questions using the pyloric pattern generating circuits in the stomatogastric nervous system of two crab species, Hemigrapsus sanguineus and Carcinus maenas that have seen a worldwide expansion in recent decades.
Results and discussion: Consistent with their history as invasive species, we find that pyloric activity showed a broad temperature robustness (>30°C). Moreover, the temperature-robust range was dependent on habitat temperature in both species. Warm-acclimating animals shifted the critical temperature at which circuit activity breaks down to higher temperatures. This came at the cost of robustness against cold stimuli in H. sanguineus, but not in C. maenas. Comparing the temperature responses of C. maenas from a cold latitude (the North Sea) to those from a warm latitude (Spain) demonstrated that similar shifts in robustness occurred in natural environments. Our results thus demonstrate that neuronal temperature robustness correlates with, and responds to, environmental temperature conditions, potentially preparing animals for changing ecological conditions and shifting habitats.
Background
Phylogenomic studies over the past two decades have consolidated the major branches of the arthropod tree of life. However, especially within the Chelicerata (spiders, scorpions, and kin), interrelationships of the constituent taxa remain controversial. While sea spiders (Pycnogonida) are firmly established as sister group of all other extant representatives (Euchelicerata), euchelicerate phylogeny itself is still contested. One key issue concerns the marine horseshoe crabs (Xiphosura), which recent studies recover either as sister group of terrestrial Arachnida or nested within the latter, with significant impact on postulated terrestrialization scenarios and long-standing paradigms of ancestral chelicerate traits. In potential support of a nested placement, previous neuroanatomical studies highlighted similarities in the visual pathway of xiphosurans and some arachnopulmonates (scorpions, whip scorpions, whip spiders). However, contradictory descriptions of the pycnogonid visual system hamper outgroup comparison and thus character polarization.
Results
To advance the understanding of the pycnogonid brain and its sense organs with the aim of elucidating chelicerate visual system evolution, a wide range of families were studied using a combination of micro-computed X-ray tomography, histology, dye tracing, and immunolabeling of tubulin, the neuropil marker synapsin, and several neuroactive substances (including histamine, serotonin, tyrosine hydroxylase, and orcokinin). Contrary to previous descriptions, the visual system displays a serial layout with only one first-order visual neuropil connected to a bilayered arcuate body by catecholaminergic interneurons. Fluorescent dye tracing reveals a previously reported second visual neuropil as the target of axons from the lateral sense organ instead of the eyes.
Conclusions
Ground pattern reconstruction reveals remarkable neuroanatomical stasis in the pycnogonid visual system since the Ordovician or even earlier. Its conserved layout exhibits similarities to the median eye pathway in euchelicerates, especially in xiphosurans, with which pycnogonids share two median eye pairs that differentiate consecutively during development and target one visual neuropil upstream of the arcuate body. Given multiple losses of median and/or lateral eyes in chelicerates, and the tightly linked reduction of visual processing centers, interconnections between median and lateral visual neuropils in xiphosurans and arachnopulmonates are critically discussed, representing a plausible ancestral condition of taxa that have retained both eye types.
The Spider Anatomy Ontology (SPD)—A Versatile Tool to Link Anatomy with Cross-Disciplinary Data
(2019)
Hibernation is a widespread adaptation in animals to seasonally changing environmental conditions. In the face of global anthropogenic change, information about plastic adjustments to environmental conditions and associated mortality costs are urgently needed to assess population persistence of hibernating species. Here, we used a five-year data set of 1047 RFID-tagged individuals from two bat species, Myotis nattereri and Myotis daubentonii that were automatically recorded each time they entered or left a hibernaculum. Because the two species differ in foraging strategy and activity pattern during winter, we expected species–specific responses in the timing of hibernation relative to environmental conditions, as well as different mortality costs of early departure from the hibernaculum in spring. Applying mixed-effects modelling, we disentangled population-level and individual-level plasticity in the timing of departure. To estimate mortality costs of early departure, we used both a capture mark recapture analysis and a novel approach that takes into account individual exposure times to mortality outside the hibernaculum. We found that the timing of departure varied between species as well as among and within individuals, and was plastically adjusted to large-scale weather conditions as measured by the NAO (North Atlantic Oscillation) index. Individuals of M. nattereri, which can exploit milder temperatures for foraging during winter, tuned departure more closely to the NAO index than individuals of M. daubentonii, which do not hunt during winter. Both analytical approaches used to estimate mortality costs showed that early departing individuals were less likely to survive until the subsequent hibernation period than individuals that departed later. Overall, our study demonstrates that individuals of long-lived hibernating bat species have the potential to plastically adjust to changing climatic conditions, although the potential for adjustment differs between species.
This thesis draws a comprehensive picture about the radiation and diversification of truncatelloidean gastropods across the south pacific. It covers three more specifc studies focussing on the Truncelloideans from Fiji, Vanuatu and New Caledonia, respectively. And a conclusive analysis that combines the results of the three more specific studies and enhances them using species from the Austral Islands, Lord Howe Island, the Indonesian island Sulawesi as well as several species from New Zealand and Australia. Molecular phylogenies were calculated using four nuclear gene fragments (ITS2; 18S rRNA; 28S rRNA and Histone 3) besides the mitochondrial COI and 16S rRNA. Further molecuular data was used to calculate dated phylogenies, perform ancestral range reconstructions and develop a modified molecular barcoding approach.
Abstract
Emperor penguins breed during the Antarctic winter and have to endure temperatures as low as −50 °C and wind speeds of up to 200 km h−1. To conserve energy, they form densely packed huddles with a triangular lattice structure. Video recordings from previous studies revealed coordinated movements in regular wave-like patterns within these huddles. It is thought that these waves are triggered by individual penguins that locally disturb the huddle structure, and that the traveling wave serves to remove the lattice defects and restore order. The mechanisms that govern wave propagation are currently unknown, however. Moreover, it is unknown if the waves are always triggered by the same penguin in a huddle. Here, we present a model in which the observed wave patterns emerge from simple rules involving only the interactions between directly neighboring individuals, similar to the interaction rules found in other jammed systems, e.g. between cars in a traffic jam. Our model predicts that a traveling wave can be triggered by a forward step of any individual penguin located within a densely packed huddle. This prediction is confirmed by optical flow velocimetry of the video recordings of emperor penguins in their natural habitat.
Flies form high-density associations with human settlements and groups of nonhuman primates and are implicated in transmitting pathogens. We investigate the movement of nonhuman primate-associated flies across landscapes surrounding Kibale National Park, Uganda, using a mark–recapture experiment. Flies were marked in nine nonhuman primate groups at the forest edge (x̄ = 929 flies per group), and we then attempted to recapture them in more anthropized areas (50 m, 200 m and 500 m from where marked; 2–21 days after marking). Flies marked in nonhuman primate groups were recaptured in human areas (19/28,615 recaptured). Metabarcoding of the flies in nonhuman primate groups revealed the DNA of multiple eukaryotic primate parasites. Taken together, these results demonstrate the potential of flies to serve as vectors between nonhuman primates, livestock and humans at this biodiverse interface.
Many of the world’s most biodiverse regions are found in the poorest and second most populous continent of Africa; a continent facing exceptional challenges. Africa is projected to quadruple its population by 2100 and experience increasingly severe climate change and environmental conflict—all of which will ravage biodiversity. Here we assess conservation threats facing Africa and consider how these threats will be affected by human population growth, economic expansion, and climate change. We then evaluate the current capacity and infrastructure available to conserve the continent’s biodiversity. We consider four key questions essential for the future of African conservation: (1) how to build societal support for conservation efforts within Africa; (2) how to build Africa’s education, research, and management capacity; (3) how to finance conservation efforts; and (4) is conservation through development the appropriate approach for Africa? While the challenges are great, ways forward are clear, and we present ideas on how progress can be made. Given Africa’s current modest capacity to address its biodiversity crisis, additional international funding is required, but estimates of the cost of conserving Africa’s biodiversity are within reach. The will to act must build on the sympathy for conservation that is evident in Africa, but this will require building the education capacity within the continent. Considering Africa’s rapidly growing population and the associated huge economic needs, options other than conservation through development need to be more effectively explored. Despite the gravity of the situation, we believe that concerted effort in the coming decades can successfully curb the loss of biodiversity in Africa.
Abstract
Pikeperch (Sander lucioperca) has become a species of interest in aquaculture. It is a popular and economically valuable food fish and can produce high numbers of offspring. However, during early development, there are transition phases when high mortality rates concur with growth changes, vital organ transformations and a limited energy budget. Up to now, no study focused on the developmental adaption of muscle tissue in pikeperch, regardless of muscle tissue influencing essential traits such as locomotion and thus the competence to hunt prey and avoid predators. In the present study, therefore, the developmental myogenesis of pikeperch was analysed using specimens from early embryonic to larval development. Myogenic and developmental genes were utilized to gain insights into transcriptomic regulation during these stages by applying a nanofluidic qPCR approach. Result, three phases of myogenic gene expression, during somitogenesis, during the late embryonic development and during the larval development were detected. Increased myostatin expression showed an interim arrest of muscle formation between embryonic and larval myogenesis. Expression patterns of satellite cell gene markers indicated an accumulation of stem cells before myogenesis interruption. The here gained data will help to broaden the knowledge on percid myogenesis and can support pikeperch rearing in aquaculture.
Predation is a major evolutionary driver of animal adaptation. However, understanding of anti-predator evolution is biased toward vertebrate taxa. Cephalopoda, a class in the invertebrate phylum Mollusca, are known for their diverse anti-predator strategies, characterised by their behavioural flexibility. While ancestral cephalopods were protected by a hard outer shell, extant cephalopods have greatly reduced their reliance on physical defences. Instead, cephalopods have evolved highly developed senses to identify potential threats, cryptic skin patterns to avoid detection, startle responses to deter attack, and elaborate means of escape. While cephalopod anti-predator repertoires are relatively well described, their evolution, and the selective pressures that shaped them, have received much less attention. This is despite their potential relevance, in turn, to elucidate evolution of the remarkable cognitive abilities of cephalopods. Here, we review cephalopod anti-predator evolution, considering four key aspects: (i) shell reduction and loss; (ii) the skin patterning system; (iii) the ecological context accompanying the evolution of advanced cognit.ive abilities; (iv) why the evolutionary trajectory taken by cephalopods is so unique among invertebrates. In doing so, we consider the unique physiology of cephalopods and discuss how this may have constrained or aided the development of their anti-predator repertoire. In particular, cephalopods are poorly equipped to defend themselves physically and escape predation by fish, due to a lack of comparable weaponry or musculature. We argue that this may have selected for alternative forms of defence, driving an evolutionary trajectory favouring crypsis and complex behaviours, and the promotion of sensory and cognitive adaptations. Unravelling the complexities of cephalopod anti-predator evolution remains challenging. However, recent technological developments available for cephalopod field and laboratory studies, coupled with new genomic data and analysis approaches, offer great scope to generate novel insights.
The need for the diversification of utilised species has emerged in the present aquaculture
production environment. Shifts in consumer interest, climate change-induced temperature
increases, and major fish disease outbreaks have put a strain on this industry. In this context,
the pikeperch (Sander lucioperca) has become a new target species for aquaculture in Central
Europe. This new aquaculture focus species exhibits high numbers of offspring, fast growth,
and high consumer acceptance. It can also effectively deal with higher temperatures and turbid
water. However, the rate of successful rearing is still low, as various developmental
transformations and environmental effects commonly lead to high mortality rates during the
early ontogenetic stages. The aim of this doctoral project was thus to obtain insight into
embryonic to larval developmental changes during pikeperch ontogeny. Specifically, the times
of change that influence survival were of focus. Based on the available literature, particular
attention was paid to general growth patterns and the connected developmental changes, the
determination of myogenesis gene marker expression changes, and the support of animal
welfare efforts for pikeperch rearing procedures. To achieve the aims of the study, a methodical
setup consisting of morphometric and developmental observations was combined with
transcriptome gene marker analysis for the different ontogenetic stages.
Three developmental phases were differentiated during the embryo-larval transition. Each of
these possessed distinct growth patterns with different growth rates. The intermediate
threshold phase showed internal organ development that focused on digestive, neuronal, and
heart tissues. Three activity phases of myogenesis were determined: during early embryonic
development, before hatching, and after hatching during the larval stages. Therefore, muscle
development seemed to be regulated to balance energy expenditures. Additionally, two
coinciding skeletogenic phases were found. Furthermore, a cell line from whole embryos was
developed to support the replacement of animals in future experimental setups. A software
system for video analyses was developed to support rearing procedures in aquaculture
facilities. This prototype can be used to automate the counting of specimens and thus allows
for faster responses to increasing mortalities. Based on the results of this thesis project, further
insights into the early development of pikeperches were obtained. This will facilitate the design
and adaptation of raising and husbandry protocols, which can help to further establish
pikeperch as an aquaculture species and support its application in modern recirculatory
systems.
Having been regarded as wastelands until quite recently, wetlands are increasingly acknowledged as ecosystems of high biodiversity. Wetland restoration projects are often accompanied by the implementation of specific species management programs. Naturally, for effective management measures, profound knowledge of the target speciesʼ ecological requirements is obligatory, including habitat selection, feeding ecology as well as spatial behaviour such as movements within and between patches of suitable habitat. Yet, big knowledge gaps exist for many marshland birds which is particularly true for highly secretive species such as rails and crakes. Considered as the least known among the Palaearctic breeding birds, most information about the Baillon's Crake Zapornia pusilla is only anecdotic, resulting in strong uncertainties with regard to the species' distribution, population sizes, status, migratory behaviour as well as ecological requirements. This can be mainly attributed to the species' skulking behaviour and its seemingly highly erratic occurrence. Baillon's Crakes in the Western Palaearctic and Palaeotropics are referred to as the subspecies Z. p. intermedia. While European breeding birds are assumed to winter in sub-Saharan wetlands, African populations are considered rather to be itinerant with local movements induced by seasonal or anthropogenic habitat changes. However, for both migratory movements, major directions or routes are unknown. The discovery of a large number of Baillon's Crakes presumably wintering in the floodplains of the Parc National des Oiseaux du Djoudj (PNOD), situated in the Senegal River Delta, WAfrica, initiated this thesis. The main aim of the study was, firstly, to clarify the status and size of this population and assess its connectivity to European breeding population(s). Secondly, in order to improve the knowledge about the species' ecological requirements as a basis for the National Parks conservation management, habitat selection, spatial behaviour as well as dietary selectivity were investigated. The major part of the fieldwork was performed in PNOD in the course of the dry season during periods of 1.5 - 2.5 months from December - March 2009, 2010 and 2013. Baillon's Crakes were mainly caught with cage traps, ringed and common measurements were taken, including moult status. Skin tissue as well as one rectrice was sampled for DNA and stable isotope analyses. This was also done for Baillon's Crakes caught in European breeding grounds in Germany, Montenegro and Southern Spain. For dietary analyses, faecal samples were collected in PNOD in winter 2009/2010. Furthermore, some individuals were equipped with radio-transmitters to determine home range size and habitat selection. For the identification of the most relevant habitat parameters both on a population as well as on the individuals' level, we used a vegetation map based on satellite imagery covering the entire Djoudj area as well as maps generated on the basis of aerial photographs taken at two study sites.
Flies are implicated in carrying and mechanically transmitting many primate pathogens. We investigated how fly associations vary across six monkey species (Cercopithecus ascanius, Cercopithecus mitis, Colobus guereza, Lophocebus albigena, Papio anubis, and Piliocolobus tephrosceles) and whether monkey group size impacts fly densities. Fly densities were generally higher inside groups than outside them, and considering data from these primate species together revealed that larger groups harbored more flies. Within species, this pattern was strongest for colobine monkeys, and we speculate this might be due to their smaller home ranges, suggesting that movement patterns may influence fly–primate associations. Fly associations increase with group sizes and may thus represent a cost to sociality.
Target Mechanisms of the Cyanotoxin Cylindrospermopsin in Immortalized Human Airway Epithelial Cells
(2022)
Cylindrospermopsin (CYN) is a cyanobacterial toxin that occurs in aquatic environments worldwide. It is known for its delayed effects in animals and humans such as inhibition of protein synthesis or genotoxicity. The molecular targets and the cell physiological mechanisms of CYN, however, are not well studied. As inhalation of CYN-containing aerosols has been identified as a relevant route of CYN uptake, we analyzed the effects of CYN on protein expression in cultures of immortalized human bronchial epithelial cells (16HBE14o−) using a proteomic approach. Proteins whose expression levels were affected by CYN belonged to several functional clusters, mainly regulation of protein stability, cellular adhesion and integration in the extracellular matrix, cell proliferation, cell cycle regulation, and completion of cytokinesis. With a few exceptions of upregulated proteins (e.g., ITI inhibitor of serine endopeptidases and mRNA stabilizer PABPC1), CYN mediated the downregulation of many proteins. Among these, centrosomal protein 55 (CEP55) and osteonectin (SPARC) were significantly reduced in their abundance. Results of the detailed semi-quantitative Western blot analyses of SPARC, claudin-6, and CEP55 supported the findings from the proteomic study that epithelial cell adhesion, attenuation of cell proliferation, delayed completion of mitosis, as well as induction of genomic instability are major effects of CYN in eukaryotic cells.
Abstract
Climate change may force organisms to adapt genetically or plastically to new environmental conditions. Invasive species show remarkable potential for rapid adaptation. The ovoviviparous New Zealand mud snail (NZMS), Potamopyrgus antipodarum, has successfully established across Europe with two clonally reproducing mitochondrial lineages since its arrival in the first half of the 19th century. Its remarkable variation in shell morphology was shown to be fitness relevant. We investigated the effects of temperature on shell morphology across 11 populations from Germany and the Iberian Peninsula in a common garden across three temperatures. We analyzed size and shape using geometric morphometrics. For both, we compared reaction norms and estimated heritabilities. For size, the interaction of temperature and haplotype explained about 50% of the total variance. We also observed more genotype by environment interactions indicating a higher degree of population differentiation than in shape. Across the three temperatures, size followed the expectations of the temperature‐size rule, with individuals growing larger in cold environments. Changes in shape may have compensated for changes in size affecting space for brooding embryos. Heritability estimates were relatively high. As indicated by the very low coefficients of variation for clonal repeatability (CVA), they can probably not be compared in absolute terms. However, they showed some sensitivity to temperature, in haplotype t more so than in z, which was only found in Portugal. The low CVA values indicate that genetic variation among European populations is still restricted with a low potential to react to selection. A considerable fraction of the genetic variation was due to differences between the clonal lineages. The NZMS has apparently not been long enough in Europe to accumulate significant genetic variation relevant for morphological adaptation. As temperature is obviously not the sole factor influencing shell morphology, their interaction will probably not be a factor limiting population persistence under a warming climate in Europe.
Presumably every organism on earth is involved in at least one mutualistic interaction with one or several other species. To interact with each other, the species need traits that provide benefits to the partner species. Surprisingly, the function of traits for the stabilization of mutualisms has rarely been investigated, despite of a general lack of knowledge how mutualisms are maintained. The aim of this work was to find functional traits, which stabilize the mutualism between a bat species and a carnivorous pitcher plant in Northern Borneo. Kerivoula hardwickii is the only bat species known to roost in pitcher-shaped trapping organs of Palaeotropical pitcher plants (Nepenthes). These bats fertilize the pitcher plant Nepenthes hemsleyana with their nutritious nitrogen-rich faeces while roosting inside the pitchers. The plants have outsourced capture and digestion of arthropod prey to the bats on which they strongly rely for nutrient acquisition. The bats in contrast are less dependent on their mutualism partner as they also roost in pitchers of two further Nepenthes species as well as in developing furled leaves of various plant species in the order Zingiberales. In earlier studies, we found that N. hemsleyana outcompetes alternative roosts by providing high-quality roosts for the bats. However, which traits exactly stabilize the mutualism between K. hardwickii and N. hemsleyana was still unclear. I found that both the bats and the pitcher plants show traits, which have the potential to stabilize their interaction. On the level of morphological traits, I found that the pitchers have a low fluid level and a particular shape that provide just enough roosting space for one individual of the solitary K. hardwickii, a mother with juvenile or a mating couple. The bats have enlarged thumb and foot pads that enable them to cling to the smooth surfaces of their roosts without using their claws. This avoids damage to the sensitive N. hemsleyana pitchers. On the level of communicational traits, again N. hemsleyana acquired morphological structures that act as effective ultrasound-reflectors, which guide the echo-orientating bats to the opening of the pitchers and help the bats to identify their mutualism partner. The bats’ calls on the other hand are characterized by extraordinary high starting frequencies and broad bandwidths, which enable K. hardwickii to easily locate pitchers of N. hemsleyana and other Nepenthes species in their dense habitats. Finally, on the level of behavioural traits the bats often but not always prefer their mutualism partner to other roosts when they can select roosts in their natural environment or in behavioural experiments. The reason for this behaviour seems to be a combination of 1) N. hemsleyana’s superior quality compared to alternative roosts and 2) different roosting traditions of the bats. In conclusion, the mutualism between bats and pitcher plants is asymmetric as N. hemsleyana is more dependent on K. hardwickii than vice versa. For the plants bat faeces present their most important nutrient source. In contrast, K. hardwickii can select between alternative roosting plants. This asymmetric dependency is reflected in the specifity and function of the traits that stabilize the mutualism in each of the two involved species. Especially on the morphological level, N. hemsleyana seems to have evolved several traits that perfectly fit to K. hardwickii. In contrast, the bats’ traits more generally facilitate their roosting in funnel-shaped plant structures and their occurrence in cluttered habitats. Thus, they are probably exaptations (i.e. traits that evolved for another reason) that are nevertheless functional and stabilize the mutualism with N. hemsleyana. This plant‘s superior roost quality is likely a consequence of the competition with alternative roosting plants and is a pre-requisite for the bats to prefer N. hemsleyana. Moreover, my study confirms earlier findings that asymmetric dependencies support the stabilization of mutualistic interactions. Finally, my work indicates that the specifity of functional traits can be used as a measure to determine mutual dependencies of mutualistic partners.
Bats belong to the most gregarious and diverse mammals with highly complex social behaviors. Despite extensive research on their ecology and social behavior in some bat species, gained insights are restricted to only few of the more than 1300 species. In the recent past, bats have also become a central topic of a different branch of research: Since the 1990s bats came to the fore of virologists and immunologists due to the bats’ apparent importance as reservoir hosts and vectors of several (mostly tropical) diseases. While this research is focused mainly on emerging infectious diseases linked to bats, and their zoonotic potential, little has been invested regarding the link between disease transmission and bat social systems.
In my work, I aim at filling this gap by merging automated daily roosting observations, social network analysis, and a virological screening in Natterer’s bats (Myotis nattereri). In a collaborative approach, my co-workers and I analyzed the social structure of individually marked Natterer’s bats, their astrovirus detection rate and transmission pathways within their colony, as well as roosting interactions between different co-occurring con- and heterospecific bat colonies.
We discovered Natterer’s bats to display a very divergent social network structure that contradicts the findings of previous studies on large fission-fusion groups. Contrary to the modular social network structure found in e.g. primates or other bats species, the social network of Natterer’s bats consists of only one highly interconnected community. Moreover, although the close proximity between bat hosts in the colony should strongly promote direct transmission, we found indications that astrovirus infections follow at least partly an indirect transmission pathway via contaminated roost use. Lastly, our results prove that co-occurring con- and heterospecific bat colonies, e.g. as in this study Natterer’s bats, brown long-eared bats and Bechstein’s bats, can influence each other in their roost use by avoiding conspecific roosts and by being attracted towards those of heterospecifics. This holds implication for the transmission of parasites and pathogens within and between different colonies with opportunities for spillovers. To conclude, this multidisciplinary study led to valuable insights in the hitherto hidden mechanisms within and among bat colonies.
Dwarf spiders (Linyphiidae, Erigoninae) are especially suitable for sexual selection research as many of them exhibit sexual dimorphism, with males possessing modified prosomata. In those species that have been investigated in detail the modified structures are equipped with a glandular tissue that produces secretions, which the females contact and take up during courtship/copulation. The time of secretion release, and refilling of the reservoirs was analysed on an ultrastructural level in male Oedothorax retusus. The results suggest that the main function of the secretions is gustatorial courtship and not the emission of volatile pheromones for mate attraction. Mating decisions and reproductive success are influenced by secondary sexual traits that evolved under sexual selection. However, an individual´s nutritional status is also important for mate choice. Since spiders are regularly exposed to limited prey availability, adult feeding status can be considered an important component of spider mating behaviour. In order to test for the effects of dietary restriction, females of the closely related species O. retusus and O. apicatus were subject to a short period of food shortage. The effects of low- (LD) vs. high-diet (HD) treatment on courtship, mating probability and behaviour, and reproduction were analysed. We found that short phases of diet restriction as adults have a high impact on copulation and reproduction in the two dwarf spider species. Whenever females mate with more than one male, and sperm is stored prior to fertilization, males may suffer from sperm competition. Mating plugs that block the female genital openings after mating are a male strategy to avoid sperm competition. Although mating plugs occur in many species, their function and origin has hardly been investigated. O. retusus males transfer amorphous material onto the female genitalia during mating. We investigated the location of plug production using x-ray microtomography (μCT) as well as light and transmission electron microscopy (TEM). Furthermore, we asked whether males are limited in the production of the amorphous plug material in successive matings. The plug material is produced in a gland inside the male pedipalp and stored close to the blind end of the sperm storage compartment. The size of the first plug a male produced significantly influenced the size of subsequent plugs. Obviously, males do not possess unlimited amounts of plug material in a certain period, which may severely limit their ability to secure paternity through subsequent mating plugs. Even though mating plugs seem to be an obvious means to secure paternity, their potential in securing paternity depends on their mechanical efficacy and persistence. Consequently, the influence of the size of the plug material (mating duration as a proxy) and the age of the mating plug (time interval between successive copulations) on its efficacy was investigated. Small and fresh plugs were least effective, whereas large plugs were highly effective. We were able to show that mating plugs in O. retusus are a powerful mechanical safeguard whose efficacy varies with plug size and age. Genitalia in animals with internal fertilization are complex, species-specific, and underlie rapid evolution. In spiders, male and female genitalia are paired, and have to interact during mating, which results in an even higher complexity. Pedipalps (transformed pair of legs) in male spiders are used as secondary sperm transfer organs that are not directly connected to the gonads. Due to the high complexity of male pedipalps, it has been taken for granted that pedipalps are side specific and cannot be used flexibly into either female copulatory opening. We investigated potential flexible pedipalp use in O. retusus. Our findings demonstrate a flexible insertion mode in a dwarf spider with complex pedipalps but relatively simple female genitalia. Our findings corroborate sexual selection as the selective regime for the evolution of complex and diverse genitalia. The results of this thesis show how complex sexual selection acts in the dwarf spiders O. retusus and O. apicatus. It shapes the evolution of male and female genitalia, affects mate choice (pre- and postcopulatory), mating behaviour, and influences mating success and reproduction. All these factors and traits affect an individual´s evolutionary fitness, and their interactions help to understand how sexual selection acts.
The Common Tern (Sterna hirundo) is one of Germany’s farthest migrating bird species. Ringing studies have shown the use of the East Atlantic flyway, and according to their main wintering areas at the western and southern African coasts, German and European Common Tern populations have been divided into two allohiemic groups. However, first ring recoveries of German Common Terns in Israel indicated that some of the birds breeding in eastern Germany cross central Europe and migrate along the eastern African coast. To investigate the migratory behavior of Common Terns from East Germany, we fitted 40 Common Terns breeding in a colony at the German Baltic coast with light-level geolocators. Twenty-four loggers with analyzable datasets could be retrieved, revealing two different migratory strategies within one population. Seventeen individuals (70.83%) used the eastern Atlantic flyway and spent the winter at the western African coast, the Gulf of Guinea and the southern African coast, while the other individuals (n = 7; 29.17%) crossed central Europe, migrated along the eastern African coast and overwintered in the Mozambique Channel and South African coast. We, therefore, suggest to add a third allohiemic group to complement the picture of European Common Tern migration. Moreover, our results provide new knowledge and open new questions, which can be used for future studies regarding the evolution of different migratory strategies and its consequences in relation to climate change.
Relative importance of plastic and genetic responses to weather conditions in long-lived bats
(2022)
In the light of the accelerating pace of environmental change, it is imperative to understand how populations and species can adapt to altered environmental conditions. This is a crucial step in predicting current and future population persistence and limits thereof. Genetic adaption and phenotypic plasticity are two main mechanisms that can mediate the process of adaptation and are of particular importance for non-dispersing species. While phenotypic plasticity may enable individuals to cope with short term environmental changes, genetic adaptation will often be required for populations to survive in situ over longer time spans. However, a rapid genetic response is expected particularly in species with fast life histories or large population sizes, leaving species with slow life histories potentially at higher extinction risk. The Bechstein’s bat (Myotis bechsteinii) is a mammal of 10 g weight that - despite its small size - is characterized by a slow life history, with low reproductive output and long lifespan, and is already considered to be of high conservation concern. Past work demonstrated body size to be a highly fitness-relevant trait in Bechstein’s bats. Body size is further known to be a pivotal trait shaping the pace of life histories in numerous species. Simultaneously, many studies reported noteworthy changes in body size as a response to shifting environments across different taxa. This suggested a potential for high plasticity in this trait in Bechstein’s bats as well; however, changes in body size could have vital impacts on demographic rates.
Therefore, this dissertation investigated the following questions: firstly, what shapes the fundamental development of body size in M. bechsteinii, and, specifically, is there an impact of weather conditions on body size? If so, in what form and magnitude? Secondly, how does body size subsequently influence the pace of life in females? What is the cost of a faster or slower pace of life, and how does fitness compare across individuals with slow and fast life histories? And finally, to what extent can changes in body size be attributed to either phenotypic plasticity or genetic adaptation? What is the evolutionary potential of body size in the populations? And, consequently, what implications can we draw regarding population persistence of these colonies?
To answer these questions, we analyzed a long-term dataset of over two decades collected from four wild Bechstein’s bat colonies. We used individual-based data on survival, reproduction and body size, built multi-generational pedigrees, and combined everything with meteorological data. In Manuscript 1 we found that, in contrast to the declining body size observed in many species, body size in Bechstein’s bats increased significantly over the last decades. We demonstrated that ambient temperature was linked to the development of body size and identified a sensitive time period in the prenatal growth phase, in which body size was most susceptible to the impact of temperature. We established that warmer summers resulted in larger bats, but that these large bats had higher mortality risks throughout their lives. Manuscript 2 then revealed the influence of body size on the pace of life in Bechstein’s bats and demonstrated high plasticity in intraspecific life history strategies. Large females were characterized by a faster pace of life and shorter lifespans, but surprisingly, lifetime reproductive success remained remarkably stable across individuals with different body sizes. The acceleration of their pace of life means that larger females compensated for their reduced longevity by an earlier reproduction and higher fecundity to reach similar overall fitness. Ultimately, differences in body size resulted in changes in population growth rate via the impact of size on generation times. Results of Manuscript 3 were then able to clarify the extent to which changes in body size were founded on either phenotypic plasticity or genetic adaptation. We demonstrated a particularly low heritability in hot summers, indicating that variance in body size was mostly driven by phenotypic plasticity, with few genetic constraints. During cold summers, behavioural adaptations by reproducing bats seem to be able to mitigate negative effects of cold temperatures. These behaviours, such as social aggregation or preference for warm roosts, are, however, essentially irrelevant in hot environments. In addition, a low evolvability of forearm length points to a low capacity to respond to selection pressures associated with the trait.
We can conclude that body size in M. bechsteinii has increased over the last two decades as a response to global warming and is only slightly constrained by its genetic underpinnings. We can further demonstrate a direct link between body size and the pace of life histories in the Bechstein’s bat populations and how changes in body size impact demographic rates via this linkage. In the context of climate change and hotter summers, our findings consequently suggest that body size will likely increase further if warm summers continue to become more frequent. Whether this plastic response of body size proves to be adaptive in the long term, however, remains to be seen. While, up to this point, switching to a faster life history has been successful in compensating fitness losses, this strategy requires sufficient habitat quality and is likely risky in times when extreme weather events are becoming more frequent, as predicted by most climate change scenarios.
Abstract
Aim
Species ranges are highly dynamic, shifting in space and time as a result of complex ecological and evolutionary processes. Disentangling the relative contribution of both processes is challenging but of primary importance for forecasting species distributions under climate change. Here, we use the spectacular range expansion (ca. 1000 km poleward shift within 10 years) of the butterfly Pieris mannii to unravel the factors underlying range dynamics, specifically the role of (i) niche evolution (changes in host‐plant preference and acceptance) and (ii) ecological processes (climate change).
Location
Provence‐Alpes‐Côte d’Azur, France; North Rhine‐Westphalia, Rhineland‐Palatinate and Hesse, Germany.
Taxon
Insect and angiosperms.
Methods
We employed a combination of (i) common garden experiments, based on replicated populations from the species’ historical and newly established range and host‐plant species representative for each distribution range, co‐occurrence analyses and (ii) grid‐based correlative species distribution modelling (SDM) using Maxent.
Results
We observed changes in oviposition preference, with females from the newly established populations showing reduced host‐plant specialization and also an overall increased fecundity. These changes in behaviour and life history may have enabled using a broader range of habitats and thus facilitated the recent range expansion. In contrast, our results indicate that the range expansion is unlikely to be directly caused by anthropogenic climate change, as the range was not constrained by climate in the first place.
Main conclusions
We conclude that evolution of a broader dietary niche rather than climate change is associated with the rapid range expansion, and discuss potential indirect consequences of climate change as trigger for the genetic differences found. Our study thus illustrates the importance of species interactions in shaping species distributions and range shifts, and draws attention to indirect effects of climate change. Embracing this complexity is likely the key to a better understanding of range dynamics.
Background
The ‘wallflower’ hypothesis proposes females mate indiscriminately to avoid reproductive delays. Post-copulatory mechanisms may then allow ‘trading up’, favouring paternity of future mates. We tested links between pre- and post-copulatory choice in Latrodectus geometricus female spiders paired sequentially with two males. These females copulate as adults or as subadults and store sperm in paired spermathecae. Choosy adults have a higher risk of delays to reproduction than subadults.
Results
We predicted low pre-copulatory, but high post-copulatory choice at first matings for adults and the opposite for subadults. At second matings, we expected all females would prefer males superior to their first. We found all females mated indiscriminately at their first pairing, but in contrast to subadults, adults usually allowed only a single insertion (leaving one of their paired spermatheca empty); a mechanism of post-copulatory choosiness. Adult-mated females were more likely to remate than subadult-mated females when they became adults, showing a preference for larger males, while subadult-mated females tended to prefer males of greater size-corrected mass.
Conclusions
Our results show that the ‘wallflower’ effect and ‘trading up’ tactics can be utilized at different life stages, allowing females to employ choice even if rejecting males is costly.
In times of recent climate change, mechanisms to deal with different environments (e.g. via dispersal to other habitats, or via in-situ responses such as genetic adaptation or phenotypic plasticity) are essential. In regions showing seasonality, organisms are already adapted to regular and, thus, often predictable environmental changes. One well-known strategy to survive periods of food shortage, especially during the winter, is hibernation. Although hibernation is already an adaptation to overcome unfavourable conditions, the optimal timing of hibernation to match for example food abundance peaks is likely to be influenced by changing climatic conditions, as expected during human-induced global change. Thus, the ability to respond to changes in optimal timing of hibernation can be crucial for organisms. All hibernators are positioned at the slow end of the slow-fast life history continuum. Longevity combined with a low annual reproductive output can result in slow recovery from population crashes and is expected to be associated with slow genetic adaptation. Therefore, it is assumed that phenotypic plasticity, a rather rapid and sometimes reversible process, is a crucial mechanism in long-lived organisms to adapt to changing environments. However, how differences in individual hibernation behaviour influence mortality and whether individuals are plastic with respect to their hibernation behaviour are largely unknown.
Recent studies suggest that climatic change can influence hibernation behaviour in various species differently, in a positive or negative way. Female Columbian ground squirrels (Urocitellus columbianus) delayed their emergence from hibernation with later snow melt and lower spring temperatures. Next to the environmental impact, emergence date showed a moderate heritability in female Columbian ground squirrels. Yellow-bellied marmots (Marmota flaviventris) emerged earlier from hibernation with warmer spring temperatures which resulted in a longer growing period for their offspring and, therefore, higher survival rates. In contrast, in alpine marmots (Marmota marmota) lower snow cover due to higher temperatures and, thus, less isolation led to lower juvenile survival. Negative effects, such as reduced juvenile survival, would be of high concern, especially for long-lived species with a low reproductive output.
Bats are exceptionally long-lived compared to other mammals of the same size and often show a low reproductive output with one offspring per year. This is especially true in the temperate zone where bats, furthermore, are characterized by seasonality and depend on hibernation during winter period to survive food and water shortage. Because bats are of high conservation concern it is of prime importance to understand their ability to respond to different climatic conditions and associated mortality costs.
The basis of this study was a five-year data set of 1047 RFID-tagged individuals from two bat species, Natterer’s bats (Myotis nattereri) and Daubenton’s bats (Myotis daubentonii), that were automatically tracked when entering or leaving the joint hibernaculum, “Brunnen Meyer”, located in north-western Germany. The two species are similar sized, share demographical traits and often occupy the same areas. Nevertheless, they differ in their foraging strategy and activity pattern during hibernation period. Natterer’s bats are able to glean insects from surfaces, even at low temperatures. Daubenton’s bats depend on flying arthropods and, thus, warmer temperatures. And indeed there is evidence that Natterer’s bats are able to hunt during hibernation period, while in Daubenton’s bats a lack of feeding during the hibernation period is suggested. Furthermore, Natterer’s bats are characterized by a higher activity at the hibernaculum throughout the hibernation period, while Daubenton’s bats on average arrive earlier, stay inactive through the winter and leave later in spring.
In both species, the aim was to investigate the impact of their individual hibernation behaviour, precisely the timing of departure in late winter and early spring, on mortality, their adjustment of departure timing to the North Atlantic Oscillation Index (NAO), as well as differences within and between the two species from 2011 until 2015.
To later on estimate the potential mortality costs of departure timing, gaining knowledge about the seasonal survival pattern (winter vs. summer) in the two species was a first necessity. In birds, particularly small species were described as winter-regulated populations with a higher mortality during winter. In contrast, in hibernating mammal species, such as bats, a relatively lower or similar winter survival compared to summer survival was shown. In this study, the analysed data demonstrated that the winter 2010/2011 was exceptionally catastrophic in Natterer’s bats and did not impact Daubenton’s bats. When excluding this catastrophic winter in Natterer’ bats, our results revealed a stable winter-summer-survival difference (higher winter and lower summer survival) in adult Natterer’s and Daubenton’s bats, with inter-annual variation in the level of survival which indicates a potential environmental impact on survival. This winter-summer survival pattern is in line with the survival pattern shown for other hibernators. Juveniles always had a lower survival rate than adult bats in both species. Nevertheless, the extent to which the species differ between seasons and age classes was stronger in Daubenton’s bats. They always showed a slightly higher winter survival and a lower summer survival than Natterer’s bats. Together with the catastrophic winter 2010/2011 in Natterer’s bats, this indicates a species-specific sensitivity to the timing of specific weather events which is in line with their foraging strategies and activity pattern during hibernation period.
With respect to emergence behaviour from the hibernaculum, the results of this study suggest considerable differences among individuals within as well as between bat species. In comparison to Daubenton’s bats, Natterer’s bats tuned their emergence more closely to weather conditions, specifically the NAO, a large scale weather index related to winter severity, and showed individual variation in behavioural plasticity. In Daubenton’s bats only the females responded to changing conditions and left earlier in individually-experienced warmer and milder winters, comparable to Natterer’s bats females. A potential reason might be reproductive advantages for the females resulting in a longer growing period for their offspring. The shown higher winter survival in adult bats of both species indicated already higher energy expenditure outside the hibernaculum. Thus, leaving early, being active and staying outside longer by itself bore a risk (exposure risk effect). Under consideration of longer exposure times, early departing individuals had on top of that an increased risk to die. This was not given in each year, but a species- and year-specific pattern was revealed. Natterer’s bats were only significantly affected by early departure in 2011, while the remaining years show no significant additional risk of leaving early. In Daubenton’s bats, the years 2014 and 2015 were associated with a significantly higher mortality of leaving early. This is in line with the hypothesis that Daubenton’s bats might not be able to hunt for insects leaving too early and do so as a best out of a bad job. Nevertheless, the year-specific pattern suggests that early bats might profit from advantageous weather conditions during early spring.
An additional hint for an environmental impact on early bat survival in at least Daubenton’s bats is that the median proportion of night hours above 3 °C within five days after departure was included in the model with the lowest AIC. However, the effect was not strong enough to be selected as the best model and, therefore, further analyses are needed to investigate this first hint.
In conclusion, the reduced winter survival of juveniles compared to adults highlights the importance of considering age class effects in studies that investigate seasonal survival patterns. The stable species-specific winter-summer-survival difference with a higher winter survival compared to summer survival, as well as the one catastrophic winter in Natterer’s bats underline the importance of including seasonal survival patterns in assessing potential fitness costs of changed behaviour. Furthermore, our results suggest that long-lived hibernating bat species have the potential to plastically adjust to changing climatic conditions, but this potential differs between species. Among-individual differences in emergence together with species-specific mortality costs of early emergence suggest the potential for natural selection to shape hibernation phenology. In summary, our findings suggest species-, population- and group-specific differences in the ability to respond to changing environments and, therefore, underline the necessity to further investigate local responses in various organisms to estimate consequences of recent climate change on a wider range.
Abstract
Relatively little is known about how plant–soil feedbacks (PSFs) may affect plant growth in field conditions where factors such as herbivory may be important. Using a potted experiment in a grassland, we measured PSFs with and without aboveground insect herbivory for 20 plant species. We then compared PSF values to plant landscape abundance. Aboveground herbivory had a large negative effect on PSF values. For 15 of 20 species, PSFs were more negative with herbivory than without. This occurred because plant biomass on “home” soils was smaller with herbivory than without. PSF values with herbivory were correlated with plant landscape abundance, whereas PSF values without herbivory were not. Shoot nitrogen concentrations suggested that plants create soils that increase nitrogen uptake, but that greater shoot nitrogen values increase herbivory and that the net effect of positive PSF and greater aboveground herbivory is less aboveground biomass. Results provided clear evidence that PSFs alone have limited power in explaining species abundances and that herbivory has stronger effects on plant biomass and growth on the landscape. Our results provide a potential explanation for observed differences between greenhouse and field PSF experiments and suggest that PSF experiments need to consider important biotic interactions, like aboveground herbivory, particularly when the goal of PSF research is to understand plant growth in field conditions.
Recent climate change and its consequences for living organisms constitute one of the greatest problems of our century. Global warming entails an increase in mean temperature and the frequencies of extreme weather events. Those changes in environmental conditions affect both plants and animals. Because of their inability to escape from unsuitable environments, plants have evolved a wide spectrum of molecular programs to protect themselves against changing conditions. Responding on altered environmental conditions will change plants chemical composition and therefore also affect plants interaction with other species (e.g., predator-prey or symbiotic relationships). For instance, changes in the chemical composition of plants may influence the survival of associated herbivores. In other words, these herbivores will be affected indirectly by climate change due to changes in the suitability / quality of their food. The aim of this doctoral thesis was to discover the effects of climate change within the relationship of the butterfly Pieris napi and its host plant (Sinapis alba used here as host plant), including individual conditions (e.g. chemical compositions of plants; morphology, physiology of the butterfly) and behavior of female butterflies and larvae. In the first experiment, the influence of simulated climate change on the chemical composition of the plant Sinapis alba was investigated. The second experiment aimed to examine the influence of changes in plant composition on the butterfly P. napi. Glucosinolates (secondary compound of plants) are known to have an important effect on the preference and performance of herbivores. Therefore, in the third experiment, the impact of glucosinolates on the preference and performance of P. napi was investigated in order to see if these plant compounds had the most important influence on this butterfly. Furthermore, in the fourth experiment, it was explored whether there is a latitudinal gradient within the species´ responses to changes in its host plant. The fifth and last experiment aimed to examine, if there are general principles across species regarding indirect effects of climate change.
Climate change, simulated by different combinations of temperature and water regimes, had an effect on the plant chemistry. The combination of temperature and water availability changed plant composition substantially. Especially the amount of carbon and glucosinolates (here above all sinalbin) in S. alba plants varies between the different treatments and therefore between the different combinations of temperature and water regimes. Regarding glucosinolates, elevated temperatures increased their concentration in leaves, whereas water deficit in combination with higher temperature reversed this pattern. For carbon content, all plants, except those of the control group, showed a decreased amount of total carbon. However, simulated heat waves had no effect on plants, leading to the assumption that the plants were able to recover from heat stress sufficiently during the control phases. Changes in plant composition affected both larvae and females of the butterfly P. napi. Therefore, changed host-plant chemistry alters the plant quality for this herbivore, meaning that plants of different treatments represent different plant qualities defined by their composition. Females of P. napi may be able to differentiate between plant qualities and even show a direct preference. Therefore, glucosinolates seem to act as oviposition stimulants. However, preferring another plant quality with lower amount of glucosinolates suggest that females of this butterfly species were attracted by more than high levels of glucosinolates alone. Larvae fed with different plant qualities performed differently, indicated by smaller wings (lighter bodies) and prolonged development when fed with plants contained higher amount of the glucosinolate sinalbin. It can be assumed that a higher amount of sinalbin decreases the quality of the host plant and therefore lead to these responses. Probably larvae need to shift their resources from growth to detoxification and therewith survival. Furthermore, drought conditions during plant growth seem to reduce the overall negative effects of higher temperatures, lead to an increase of host plant quality. Larvae seem to benefit from feeding on these “double-stressed” plants. Comparison between the results of the preference and performance tests suggests that there might be a mismatch between female preference and larval performance. It seems that the stimulating effect of high concentration of glucosinolates, in this case sinalbin, misdirects females´ decision to less suitable host plants, meaning that the advantage of less competition for larvae come at costs through detoxification. Using Brassica napus plants with genetically fixed glucosinolate levels, it could be demonstrate that there must be other plant components influencing females´ oviposition behavior been seen in the choice experiment with S. alba. The comparison of German and Italian populations to changes in host-plant quality showed fewer differences between countries as expected. However, German and Italian individuals differed in their reaction to altered plant quality, at least in developmental time and larval growth rate. It seems that Italian larvae benefitted from plants grown under higher temperatures, whereas drought-stressed plants affected them negatively. German individuals in contrast seem to benefit only from water stress during plant growth. With regard to the sexes of P. napi, it seems that females respond differently than males to changes in plant quality. Furthermore, the results of the performance test on Bicyclus anynana showed that there might be some general principles for the respond of butterflies to changes of its host plant. B. anynana responded in a similar way to different host plant qualities as P. napi did, meaning that plants grown under higher temperatures and drought conditions seem to be beneficial for the larval performance.
In summary, these findings may have important implications for the indirect effects of climate change on this butterfly in natural environments. First, climate change seems to have an impact on the chemical composition of plants. Second, changes in plants caused by increasing temperature and droughts seem to influence the preference and performance of this butterfly. However, there are differences between populations, which seem to be induced by former adaptation. And third, there might be some general principles for the respond of butterflies to changes in their host plants. This thesis focuses only on possible indirect effects of climate change. However, there are direct effects, which may alter the responses of herbivores to changes in their host plant as well. Therefore, further investigations in this linkage and in other plant-herbivore relationships will be necessary to explore how climate change may alter the relationship between herbivores and their hosts.
In a changing world, phytoplankton communities face a large variety of challenges including altered light regimes. These alterations are caused by more pronounced stratification due to rising temperatures, enhanced eutrophication, and browning of lakes. Community responses toward these effects can emerge as alterations in physiology, biomass, biochemical composition, or diversity. In this study, we addressed the combined effects of changes in light and nutrient conditions on community responses. In particular, we investigated how light intensity and variability under two nutrient conditions influence (1) fast responses such as adjustments in photosynthesis, (2) intermediate responses such as pigment adaptation and (3) slow responses such as changes in community biomass and species composition. Therefore, we exposed communities consisting of five phytoplankton species belonging to different taxonomic groups to two constant and two variable light intensity treatments combined with two levels of phosphorus supply. The tested phytoplankton communities exhibited increased fast reactions of photosynthetic processes to light variability and light intensity. The adjustment of their light harvesting mechanisms via community pigment composition was not affected by light intensity, variability, or nutrient supply. However, pigment specific effects of light intensity, light variability, and nutrient supply on the proportion of the respective pigments were detected. Biomass was positively affected by higher light intensity and nutrient concentrations while the direction of the effect of variability was modulated by light intensity. Light variability had a negative impact on biomass at low, but a positive impact at high light intensity. The effects on community composition were species specific. Generally, the proportion of green algae was higher under high light intensity, whereas the cyanobacterium performed better under low light conditions. In addition to that, the diatom and the cryptophyte performed better with high nutrient supply while the green algae as well as the cyanobacterium performed better at low nutrient conditions. This shows that light intensity, light variability, and nutrient supply interactively affect communities. Furthermore, the responses are highly species and pigment specific, thus to clarify the effects of climate change a deeper understanding of the effects of light variability and species interactions within communities is important.
Global climate change is omnipresent all over the world and is affecting and challenging organisms in various ways. Species either have to adapt to the changing environmental conditions or move to new habitats in order to avoid extinction.
Possible ways for an organism to react can be dispersal, phenotypic plasticity, genetic adaptation or a combination of these factors. Among the various consequences of climate change, especially changes in temperature affect plenty of species. In ectotherms, the body temperature and associated mechanisms are strongly dependent on environmental conditions.
The aim of this work was to investigate the mechanisms underlying adaptation to thermal variation and heat stress in the widespread butterfly species <i>Pieris napi<i>.
Focusing on indicators of individual condition, including morphology, physiology and life history traits, the purpose was to specify whether the species’ responses to temperature variation have a plastic or genetic basis. In the first experiment, phenotypic variation along a latitudinal and altitudinal cline was investigated. Yellow reflectance of wings was negatively correlated with wing melanisation, providing evidence for a trade-off between a sexually selected trait (yellow color) and thermoregulation (black color). Body size decreased with increasing latitude and led to the assumption that warmer conditions are more beneficial for <i>P. napi<i> than cooler ones. An increased flight performance at higher altitudes but not latitudes may
indicate stronger challenges for flight activity in high-altitude environments.
The second experiment focused on clinal variation and plasticity in morphology, physiology and life history in F1-generation individuals reared in captivity at different temperatures. It could be shown that individuals from cooler environments were less heat-tolerant, had a longer development but were nevertheless smaller, and had more melanised wings. These differences were genetically-based. Furthermore, it could be shown that a higher developmental temperature speeded up development, reduced body size, potential metabolic activity, and wing melanisation but increased heat tolerance, documenting plastic responses.
In a third experiment, we examined physiological responses to heat stress. A transcriptome analysis revealed an upregulation in molecular chaperones under hot conditions, whereas antioxidant responses and oxidative damage remained unaffected. The antioxidant glutathione (GSH) though was reduced under both cold and hot conditions. Interestingly, Swedish individuals were characterized by higher levels of GSH, lower early fecundity, and lower larval growth rates compared with German or Italian populations, suggesting a ‘pace-of-life’ syndrome. Thus, the individuals from warmer regions show the opposite pattern with a lower investment into maintenance but a faster lifestyle.
In summary, we found clinal variation in body size, growth rates and concomitant development time, wing aspect ratio, wing melanisation and heat tolerance. The effects of high developmental temperature very likely reflect adaptive phenotypic plasticity. When speeding up development; heat tolerance is increasing while body size, potential metabolic activity and wing melanisation are decreasing. Overall, body size of <i>P. napi<i> individuals decreased from south to north while the melanisation of the wings increased. Furthermore, we found a connection between increased wing melanisation and decreased yellow reflectance, most likely caused by a trade-off between the two. We could confirm that <i>P. napi<i> individuals from warmer environments were more heat-tolerant and larger than individuals from colder environments. Due to increasing temperatures and heat waves becoming more frequent in the future, being able to cope with such conditions will be advantageous. As warmer conditions had positive effects on individual development, <i>P. napi<i> may benefit from global warming, but its association with moist habitats suggests negative consequences of climate change. We could also reveal pronounced plastic and genetic responses in <i>P. napi<i>, which may indicate high adaptive capacities. Thus, increasing temperature may not be too problematic for the species, as it seems to be rather well equipped to deal with such challenges. However, as climate change entails changes in precipitation / humidity along with temperature changes, such issues need further investigation.
Photosynthetic activity in both algae and cyanobacteria changes in response to cues of predation
(2022)
A plethora of adaptive responses to predation has been described in microscopic aquatic producers. Although the energetic costs of these responses are expected, with their consequences going far beyond an individual, their underlying molecular and metabolic mechanisms are not fully known. One, so far hardly considered, is if and how the photosynthetic efficiency of phytoplankton might change in response to the predation cues. Our main aim was to identify such responses in phytoplankton and to detect if they are taxon-specific. We exposed seven algae and seven cyanobacteria species to the chemical cues of an efficient consumer, Daphnia magna, which was fed either a green alga, Acutodesmus obliquus, or a cyanobacterium, Synechococcus elongatus (kairomone and alarm cues), or was not fed (kairomone alone). In most algal and cyanobacterial species studied, the quantum yield of photosystem II increased in response to predator fed cyanobacterium, whereas in most of these species the yield did not change in response to predator fed alga. Also, cyanobacteria tended not to respond to a non-feeding predator. The modal qualitative responses of the electron transport rate were similar to those of the quantum yield. To our best knowledge, the results presented here are the broadest scan of photosystem II responses in the predation context so far.
Organisms often employ ecophysiological strategies to exploit environmental conditions and ensure bio-energetic success. However, the many complexities involved in the differential expression and flexibility of these strategies are rarely fully understood. Therefore, for the first time, using a three-part cross-disciplinary laboratory experimental analysis, we investigated the diversity and plasticity of photoresponsive traits employed by one family of environmentally contrasting, ecologically important phytoflagellates. The results demonstrated an extensive inter-species phenotypic diversity of behavioural, physiological, and compositional photoresponse across the Chlamydomonadaceae, and a multifaceted intra-species phenotypic plasticity, involving a broad range of beneficial photoacclimation strategies, often attributable to environmental predisposition and phylogenetic differentiation. Deceptively diverse and sophisticated strong (population and individual cell) behavioural photoresponses were observed, with divergence from a general preference for low light (and flexibility) dictated by intra-familial differences in typical habitat (salinity and trophy) and phylogeny. Notably, contrasting lower, narrow, and flexible compared with higher, broad, and stable preferences were observed in freshwater vs. brackish and marine species. Complex diversity and plasticity in physiological and compositional photoresponses were also discovered. Metabolic characteristics (such as growth rates, respiratory costs and photosynthetic capacity, efficiency, compensation and saturation points) varied elaborately with species, typical habitat (often varying more in eutrophic species, such as Chlamydomonas reinhardtii), and culture irradiance (adjusting to optimise energy acquisition and suggesting some propensity for low light). Considerable variations in intracellular pigment and biochemical composition were also recorded. Photosynthetic and accessory pigments (such as chlorophyll a, xanthophyll-cycle components, chlorophyll a:b and chlorophyll a:carotenoid ratios, fatty acid content and saturation ratios) varied with phylogeny and typical habitat (to attune photosystem ratios in different trophic conditions and to optimise shade adaptation, photoprotection, and thylakoid architecture, particularly in freshwater environments), and changed with irradiance (as reaction and harvesting centres adjusted to modulate absorption and quantum yield). The complex, concomitant nature of the results also advocated an integrative approach in future investigations. Overall, these nuanced, diverse, and flexible photoresponsive traits will greatly contribute to the functional ecology of these organisms, addressing environmental heterogeneity and potentially shaping individual fitness, spatial and temporal distribution, prevalence, and ecosystem dynamics.
Unstable environments and habitats changing due to climate change force individuals to either respond by genetic adaptation, phenotypic plasticity or by dispersal to suitable environments. Theodoxus fluviatilis (Linneaus, 1758) is a good study organisms when researching phenotypic plasticity and genetic adaptation as it naturally appears in freshwater (FW) as well as brackish water (BW) and thus inhabits a wide range of environmental salinities (0-18‰). It is a euryhaline snail that can be found in shallow waters with stony ground or on Fucus spp. and has formed regional subgroups. The brackish water and the freshwater subgroups are spatially separated and the species cannot be found in areas inbetween, e.g. estuaries.
The species shows great variability in shell patterning and shell size and there is still debate whether the subgroups are distinguishable by these traits or not. The mitochdrial RNA marker cytochrome c subunit I did not show differences between the subgroups indicating that they must be closely related, but salinity tolerance has been observed to be higher in BW snails. This might be caused by the different protein expression patterns and osmolyte accumulation (measured as ninhydrin-positive substances) observed in this species in previous studies. The exact mechanisms regulating protein expression and osmolyte accumulation, however, are not fully understood yet.
Data collected for this thesis shows differences in shell size and suggests a less strict grouping of FW and BW individuals as shell sizes of one FW site are more similar to BW individuals than the other FW ones. A better salinity tolerance towards high salinities and a higher physiological salinity limit of BW snails was confirmed and extended by demonstrating an expanded tolerance range through slow acclimation to challenging salinities in snails from both subgroups. This was achieved by a shift in the slope of their reaction norms that was much more pronounced in BW snails than FW ones. S3 individuals showed a shift similar to that of BW individuals. The data for the salinity tolerance indicates that the underlying mechanism for these tolerances are a combination of phenotypic plasticity and genetic adaptation. Despite an acclimation and shift in the slope of the reaction norms and therefore an increased tolerance towards high salinities (plasticity) FW individuals from two collection sites were not able to cope with salinities as high as BW individuals (local adaptation). The general ability to mobilise free amino acids (FAA) as organic osmolytes was not the reason for this tolerance difference. Individuals from BW and FW sites were capable of accumulating quantities of FAAs equally well. Proline, alanine and urea were the most important components of the accumulated cocktail of organic osmolytes. Even though the total amount of FAAs accumulated under hyperosmotic conditions was the same in both subgroups, there were differences in the metabolic pathways involved in osmolyte accumulation in the foot muscle. The data indicates that the hydrolysis of storage proteins and the synthesis of proline and alanine are the main processes to avoid detrimental body volume shrinkage in T. fluviatilis. While FW individuals seemed to rely on the degradation of proteins and synthesis of alanine, BW individuals depended on newly synthesising proline and alanine and accumulating urea as a side product of transamination. The accumulation of urea is a new finding in aquatic living snails and has not been reported as a mechanism to avoid cell volume shrinkage in these animals.
Differing protein expression patterns were observed under control conditions across all collection sites. 9 spots showed volume changes in BW snails opposite to those of FW snails from collection sites S1 and S2. For 6 of those spots, S3 individuals showed patterns similar to those of BW individuals and for the remaining 3 they showed patterns similar to those of FW animals. The patterns observed when exposing snails to hypo- or hyperosmotic stress were not conclusive in relation to pinpointing individual spots that show the same pattern in all collection sites, but revealed the heterogeneity of protein expression in snails from the different collection sites and in the process of osmoregulation. It also showed the general tendency of protein reduction when snails where under osmotic stress of either kind (hypo- or hyperosmotic), which supports the hypothesis of storage protein degradation.
The investigation of an ANP-receptor showed two variations of the encoding sequence expressed in T. fluviatilis. S3 individuals as well as BW individuals were found to express one type, while FW individuals, with the exception of one sample expressed the other type. This showed that the FW subgroup of T. fluviatilis seems to be more heterogeneous than the BW subgroup, but also raises the question of the dispersal history of this species. The collected data indicates that T. fluviatilis individuals are firstly capable of surviving the acidity of a duck's gizzard and secondly can tolerate acute salinity changes to 16‰ when introduced into a new environment. Hence, if snails from the FW were to be transported to waters with a salinity of up to 16‰ by man, bird, drifting plants or some other means of transport, they would most likely survive and possibly be able to thrive and spread.
Under natural conditions, most parts of northeastern Germany would be covered by forests that would be dominated by beech (Fagus sylvatica) and oak (Quercus robur and Q. petraea). However, today most of the wooded area is covered by artificial monocultures of pine forests. This form of cultivation was recognised to be the cause of instability against calamities of pests as well as severe storms therefore in the early eighties of the last century this knowledge was used to start the conversion of the forests towards more nature-like stands. The ecological effects of the forest conversion on the soil, the fauna and the flora have been investigated in a nation-wide project supported by the Federal Ministry of Education and Research (BMBF) in the project “Future-oriented forest management”. The present work has been accomplished within the scope of this project and is concerned about the effects that different aspects of forest conversion have on oribatid mites. The present work shall serve to answer a number of questions about the distribution of oribatid mites and their reaction to environmental changes. The investigation was carried out on 12 plots in two sampling areas. 7 plots were chosen in the Müritz NP and 5 in Eberswalde. In both areas plots were chosen that resemble the different stages of forest conversion: one medium aged pine plot in each area, two medium aged mixed plots with pines and beeches in the Müritz NP and one mixed plot in Eberswalde as well as one beech plot in each area. Furthermore, in the Müritz NP the chance arose to investigate the effects of different age stages of the stands on the oribatid mites. Therefore, an additional young pine plot and two old mixed plots have been sampled. In Eberswalde, on the other hand, another emphasis was laid on the effects of a different nutrient content in the soil. Here, an additional pine plot and mixed plot, respectively, of a higher trophotopic level was sampled. In Eberswalde, an additional sampling was done in three plots (a beech plot, a mixed plot and a pine plot) to investigate the horizontal distribution of the oribatid mites in these habitats. The data were used along with others to ecologically characterise the different species. The sampling took place from 2000 to 2002. Within the scope of the doctoral thesis, 392 samples were analysed. 122 samples from one year from the Müritz NP and 270 samples from three years from Eberswalde were analysed. Altogether 155,450 oribatid mites from 82 taxa were found in these samples. The ecological characterisation of the species revealed that the various species react quite differently to the investigated factors. Most species occur with different abundances in different forest types, but their abundance often varies also in comparable stands of both sampling areas. This indicates that they react to climatic effects as well as to biotic and abiotic factors. The forest conversion from pine forests to beech forests causes the abundance of oribatid mites to decrease, probably due to the change of the humus form from mor or mor-like moder in pine forests to mull in beech forests, that is accompanied by a decrease of the abundance of fungi, the main food source for most oribatid mites. Furthermore, the species composition changed. Species like Camisia spinifer, Adoristes ovatus or Acrogalumna longipluma that are typical for pine forests disappeared, while other species like Achipteria coleoptrata or Chamobates voigtsi immigrated in mixed stands after the introduction of beeches. The age of the stands proved to be another important factor. The overall abundance of oribatid mites was higher in the older stands than in the younger stands, while the percentage of juvenile oribatids decreased towards the older stands. Furthermore, the dominance structure became more uneven and shifted toward a higher percentage of fungivorous oppiid and suctobelbid mites. Especially on the old mixed plots, Oppiella nova reaches a dominance value of about 60 %. The nutrient content of the soil seems to be a relatively unimportant factor on the community level as no significant differences with regard to overall abundance and the dominance structure could be recorded. However, the Canonical Correspondence Analysis showed that the nutrient content of the soil does influence the distribution of species, at least with regard to their individual abundance. In summary, it can be said that the distribution of the oribatid species is influenced by many factors, and the stocking is only one of these factors. Nevertheless, a group of four species could be established, that can be used as indicators for the success of the forest conversion towards more nature-like deciduous forests: Achipteria coleoptrata, Autogneta longilamellata, Chamobates subglobulus and C. voigtsi.
In holometabolic insects, senescence starts at sexual maturation and condition diminishes with age. Young virgin males should gain the highest mating success. Although sperm quality and quantity typically decreases with age, older males have been shown to have a higher mating success in a variety of insect taxa. Life-history theory predicts an increased aggressive and persistent courtship behaviour, due to a decrease of the residual reproductive value and thus, the opportunity for future reproduction. In the butterfly Bicyclus anynana, older males gain up to a 4x higher mating success despite a poorer condition, compared to younger males. As older males were found to court more often and for longer time bouts,suggesting a higher intrinsic motivation, there is evidence for the residual reproductive value hypothesis. On the other hand, an age-specific variation of male sex pheromones may provide females with information, being helpful to chose specific males. The latter could be males which have proven a high fitness in terms of survival, thus essentially reflecting a “good genes" hypothesis. This doctoral thesis investigated the reasons underlying old male mating advantage in B. anynana. The first study tested whether old male mating advantage prevails, even if females were unable to distinguish between older and younger males. The results were backed up by examining female rejection rates, male courtship frequency, courtship duration, time to copulation and mating duration. Older males had a significantly higher mating success compared to younger ones regardless of differences in pheromone blends or the females ability to smell. Older males courted more often and longer. The results support the residual reproductive value hypothesis. Study 2 investigated post-copulatory sexual selection in B. anynana. Females were double-mated, allowing for sperm competition and cryptic mate choice. Older males had a higher paternity success than younger ones, when the former were the last mating partner. The paternity success was balanced across age classes when older males were the first mating partner. Older males transferred larger spermatophores with higher numbers of eupyrene sperm than younger males. B. anynana does not exhibit cryptic mate choice and last-male precedence is the most probable fertilization pattern. The higher proportion of offspring sired by older males is due to significantly increased numbers of fertile sperm compared to younger males. The latter are clearly disadvantaged, as the higher sperm numbers provided by older males counteract the benefits of last-male precedence. Study 3 explored determinants of mating success in B. anynana. Successful males had longer wings, a heavier thorax, a lighter abdomen, a higher fat content, and higher phenoloxidase expression levels. Mating success seemed to be directly linked to proxies of flight performance. Successful males showed a better flight performance, in turn increasing mating success. As energy reserves are of crucial importance for flight manoeuvres, they may play a significant role in male mating success. Study 4 tested the effects of male age and mating number on spermatophore mass, sperm number, male oxidative status, and reproductive success by manipulating age and mating frequency in male B. anynana. Spermatophore mass and sperm numbers increased significantly with age, while antioxidant defences and oxidative damage declined. Female fecundity and egg-hatching success was highest when being mated with young virgin males. Antioxidant defences decreased with age, being a possible reason for the negatively affected reproductive success in females. Ejaculate quality diminished with age and mating number, despite larger spermatophores and higher sperm numbers being found in older males. Therefore, spermatophore size and sperm numbers can not be considered as reliable proxies of male condition. The final study proofed whether male sex pheromone comprise honest signals and which traits might be associated with increased pheromone titres. Pheromone titres were analysed among successful and unsuccessful males when being mated with either a control or a scent-blocked female. Both groups did not differ in pheromone levels. Successful males had significantly higher numbers of eupyrene sperm. No correlation between male pheromones and any investigated trait was found, suggesting that pheromone titres do not provide reliable information on male quality. Nothing indicates that male sex pheromones in B. anynana play a decisive role in female mate choice. Successful males generally have a better body condition, resulting in a more vigorous courtship behaviour and higher sperm numbers. Hence, variation in body condition rather than pheromone titres is more likely to determine male mating success. Mating decisions are primarily driven by male behaviour. The results suggest that old male mating advantage arises from sexual conflict.
Abstract
Sander lucioperca is an organism of growing importance for the aquaculture industry. Nonetheless, the rearing of S. lucioperca larvae is proving to be a difficult task as it is facing a high mortality rate during hatching and the change to exogenous feeding. To gain insight into growth patterns during this period, the authors analysed pikeperch embryos and larvae from 9 days before hatching to 17 days after hatch. Hereby they were able to describe a natural development by using close to natural conditions based on using a direct flow‐through supply of lake fresh water on specimens from a local wild population. The results show that between the early embryonic stages a steady growth was visible. Nonetheless, in between hatching and the start of exogenous feeding, a phase of growth stagnation took place. In the following larval stages, an increased growth with large size variations between individual specimens appeared. Both factors are conspicuous as they can indicate a starting point for cannibalism. With this analysis, the authors can provide a fundament to support the upcoming research on S. lucioperca and aid to optimize size‐sorting procedures for a higher survival of pikeperch stock in aquaculture.
Background
Haemosporidian parasites of the genus Polychromophilus infect bats worldwide. They are vectored by obligate ectoparasitic bat flies of the family Nycteribiidae. Despite their global distribution, only five Polychromophilus morphospecies have been described to date. The two predominant species, Polychromophilus melanipherus and Polychromophilus murinus, are broadly distributed and mainly infect miniopterid and vespertilionid bats, respectively. In areas where species from different bat families aggregate together, the infection dynamics and ability of either Polychromophilus species to infect other host families is poorly characterized.
Methods
We collected 215 bat flies from two bat species, Miniopterus schreibersii and Rhinolophus ferrumequinum, which sometimes form mixed clusters in Serbia. Miniopterus schreibersii is known to be frequently infected with P. melanipherus, whereas R. ferrumequinum has been observed to be incidentally infected with both Polychromophilus species. All flies were screened for Polychromophilus infections using a PCR targeting the haemosporidian cytb gene. Positive samples were subsequently sequenced for 579 bp of cytochrome b (cytb) and 945 bp of cytochrome oxidase subunit 1 (cox1).
Results
Polychromophilus melanipherus DNA was detected at six out of nine sampling locations and in all three examined bat fly species collected from M. schreibersii (Nycteribia schmidlii, n = 21; Penicillidia conspicua, n = 8; Penicillidia dufourii, n = 3). Four and five haplotypes were found for cytb and cox1, respectively. Evidence for multiple Polychromophilus haplotypes was found in 15 individual flies. These results point to a high diversity of P. melanipherus parasites in Miniopterus hosts and efficient transmission throughout the study area. A single Phthiridium biarticulatum bat fly collected from R. ferrumequinum screened positive for P. melanipherus, but only yielded a partial cox1 sequence fragment. Nevertheless, this result suggests that secondary hosts (both bat and fly species) are regularly confronted with this parasite.
Conclusions
The results of this study provide new insights into the prevalence and distribution of Polychromophilus parasites in European bats and their nycteribiid vectors. The use of bat flies for the non-invasive investigation of Polychromophilus infections in bat populations has proven to be efficient and thus represents an alternative for large-scale studies of infections in bat populations without the need to invasively collect blood from bats.
In mandibulate arthropods, the primary olfactory centers, termed olfactory lobes in crustaceans, are typically organized in distinct fields of dense synaptic neuropils called olfactory glomeruli. In addition to olfactory sensory neuron terminals and their postsynaptic efferents, the glomeruli are innervated by diverse neurochemically distinctive interneurons. The functional morphology of the olfactory glomeruli is understudied in crustaceans compared with insects and even less well understood and described in a particular crustacean subgroup, the Peracarida, which embrace, for example, Amphipoda and Isopoda. Using immunohistochemistry combined with confocal laser scanning microscopy, we analyzed the neurochemistry of the olfactory pathway in the amphipod Parhyale hawaiensis. We localized the biogenic amines serotonin and histamine as well as the neuropeptides RFamide, allatostatin, orcokinin, and SIFamide. As for other classical neurotransmitters, we stained for γ-aminobutyric acid and glutamate decarboxylase and used choline acetyltransferase as indicator for acetylcholine. Our study is another step in understanding principles of olfactory processing in crustaceans and can serve as a basis for understanding evolutionary transformations of crustacean olfactory systems.
Decision making in everyday purchase situations requires mental processing of factors that are related to the items on display. These influencing factors – called persuasive information – can take various forms, like the price level, the design of the package or the display of certain product attributes. Despite the existence of persuasive information trying to influence our buying behavior, almost nothing is known about the underlying neural mechanisms responsible for processing this information. In this thesis functional magnetic resonance imaging was used to investigate neural activity correlated with product related persuasive information. As persuasive information organic, light and regular labeled food was chosen. The 1st experiment investigated the neural correlates of visually inspected organic and regular labeled food and the influence on willingness to pay (WTP) for the displayed items. It was hypothesized that organic compared to regular labeled food will be perceived as more rewarding which should be visible by an increased activity in the ventral striatum as a central area for reward processing and by a heightened WTP. As organic label information the national German eco emblem 'Bio-Siegel' was chosen (for stimuli details see 2.1). As there is no emblem indicating regular food, an artificially created logo was used for indicating a conventional product. 40 well- known food products (e.g. milk, bread, eggs etc.) were presented to the subjects. These products were marked with the organic emblem and the same 40 products with the regular label. We found that visual inspection of organic labeled food indeed led to an increase in neural activity in the ventral striatum and to a heightened WTP, suggesting a higher subjective value for these products. The 2nd experiment investigated the neural correlates of actually administered food stimuli labeled organic, light or regular and the influence on expected and experienced taste. For organic compared to regular labeled food we hypothesized an increase in expected and experienced taste pleasantness. Furthermore, light compared to regular labeled food should lead to a decrease in expected and perceived pleasantness and intensity ratings. During the active tasting process this should be accompanied by an increase in reward-related (e.g. organic vs. regular; regular vs. light) areas like the ventral striatum medial orbitofrontal cortex or aversion-related (e.g. regular vs. organic; light vs. regular) areas as the lateral orbitofrontal cortex (lOFC) and operculum/insula. As organic label information the national German eco emblem 'Bio-Siegel' was chosen. Light label information was issued in form of the internationally used 'Bewusst-Wählen®' ('Healthy Choice') label (for stimuli details see 2.2). However, inside the scanner the written forms 'Bio', 'Light' or 'Normal' (indicating regular food) were chosen. Subjects were randomly assigned in two groups and were either confronted with the organic or the regular label (organic group) or with the light or the regular label (light group) but otherwise identical milk drink. The results show that organic compared to regular labeling of identical food stimuli indeed led to an increase in expected and experienced taste pleasantness for organic labeled food. Light compared to regular labeling of identical food stimuli led to a decrease in expected and experienced taste pleasantness and intensity for light labeled food. Moreover, taste-related activity was found in aversion related areas like the operculum insula and the lOFC for food labeled regular compared to organic and in reward-related areas like the ventral striatum for food labeled regular compared to light. The results show that persuasive food-related information influences human cognition on the behavioral and neural level; the effects were shown during visual and gustatory evaluation of the stimuli. Taken together the results demonstrate that the same stimulus can vary dramatically in personal valuation depending on the applied information.
Cryptochromes are evolutionary ancient blue-light photoreceptors that are part of the circadian clock in the nervous system of many organisms. Cryptochromes transfer information of the predominant light regime to the clock which results in the fast adjustment to photoperiod. Therefore, the clock is sensitive to light changes and can be affected by anthropogenic Artificial Light At Night (ALAN). This in turn has consequences for clock associated behavioral processes, e.g., diel vertical migration (DVM) of zooplankton. In freshwater ecosystems, the zooplankton genus Daphnia performs DVM in order to escape optically hunting predators and to avoid UV light. Concomitantly, Daphnia experience circadian changes in food-supply during DVM. Daphnia play the keystone role in the carbon-transfer to the next trophic level. Therefore, the whole ecosystem is affected during the occurrence of cyanobacteria blooms as cyanobacteria reduce food quality due to their production of digestive inhibitors (e.g., protease inhibitors). In other organisms, digestion is linked to the circadian clock. If this is also the case for Daphnia, the expression of protease genes should show a rhythmic expression following circadian expression of clock genes (e.g., cryptochrome 2). We tested this hypothesis and demonstrated that gene expression of the clock and of proteases was affected by ALAN. Contrary to our expectations, the activity of one type of proteases (chymotrypsins) was increased by ALAN. This indicates that higher protease activity might improve the diet utilization. Therefore, we treated D. magna with a chymotrypsin-inhibitor producing cyanobacterium and found that ALAN actually led to an increase in Daphnia’s growth rate in comparison to growth on the same cyanobacterium in control light conditions. We conclude that this increased tolerance to protease inhibitors putatively enables Daphnia populations to better control cyanobacterial blooms that produce chymotrypsin inhibitors in the Anthropocene, which is defined by light pollution and by an increase of cyanobacterial blooms due to eutrophication.
The goal of this thesis was to study the systematic relationships within the superfamily Sylvioidea (Aves: Passeriformes) in general and within the closely related families Acrocephalidae and Locustellidae in particular, by means of DNA sequences. Sylvioidea itself and families therein were the focus of many studies based as well on morphological characters as on DNA. Due to their morphological similarity and their presumably rapid radiation most studies failed to solve relationships between sylvioidean families and also demarcations of single families and relations within are still in progress. In this study, an enlargement of previous datasets, both taxa and number of DNA sequences, and more sophisticated analysis methods were used to improve the resolution in Sylvioidea, Acrocephalidae and Locustellidae. In addition, the applicability of barcoding in Acrocephalidae was tested. The monophyly of Sylvioidea could be supported and the families Paridae and Remizidae, which were sometimes still included, clustered among the outgroup taxa. Four families, Nicatoridae, Panuridae, Alaudidae, and Macrosphenidae constitute basal splits within Sylvioidea. The division of the former sylviid/timaliid clade in five families, Sylviidae, Leiothrichidae, Pellorneidae, Timaliidae, and Zosteropidae was supported. Scotocerca, Erythrocercus, and Hylia, previously supposed to be members of Cettiidae, were shown not to belong to this family. As the three genera are also morphologically and ecologically different, they were here proposed to be elevated to family rank, Scotocercidae, Erythrocercidae and Hyliidae, respectively. The family Acrocephalidae consisted of the four genera, Nesillas, Acrocephalus, Hippolais, and Chloropeta. In the analysis for this thesis, the latter three appeared to be non-monophyletic. One Acrocephalus species, A. aedon was sister to a clade containing four species of Hippolais as well as two out of three Chloropeta species. They were all merged in the genus Iduna, based on the DNA evidence and shared morphological and ecological characters. Iduna had priority over Hippolais or Chloropeta according to the International Code of Zoological Nomenclature. The one remaining Chloropeta species (C. gracilirostris) had to be renamed to Calamonastides as Chloropeta was no longer available for this taxon. Seven genera were included in the re-analysis of the family Locustellidae: Locustella, Bradypterus, Megalurus, Dromaeocercus, Schoenicola, Cincloramphus, and Eremiornis. Apart from the monotypic genera Dromaeocercus and Eremiornis and Schoenicola, of which only one species was included, the remaining genera were found to be non-monophyletic. One clade contained all Locustella species, Megalurus pryeri and all Asian/Oriental Bradypterus species. All species in this clade were synonymized with Locustella, as the type species of Locustella was included, whereas the type species of Bradypterus fell in a different clade. Therefore, the remaining African Bradypterus species retained their genus name, and Dromaeocercus was renamed to Bradypterus as it clustered within Bradypterus. Cincloramphus, intermingling with the remaining Megalurus species, was synonymized with the latter. Barcoding, growing in popularity for delimiting species, was tested in its applicability for Acrocephalidae. Fourteen taxa currently recognized as full species would fall under the 2% threshold of sequence divergence proposed for delimiting species using the mitochondrial cytochrome b gene. It was also shown that it is important to clarify which part of a DNA sequence is used, as different parts can give different results regarding the 2% threshold. In addition, the choice of “complete deletion” or “pairwise deletion” in calculating genetic distances is important, if incomplete are sequences used.
The modification of male pedipalps into secondary sexual intromittent organs is one of the hallmark characteristics of spiders, yet understanding the development and evolution of male genitalia across the order remains a challenging prospect. The embolus – the sclerite bearing the efferent spermatic duct or spermophor, and used to deliver sperm directly to the female genitalia during copulation – has always been considered the single unambiguously homologous palpal sclerite shared by all spider species, fundamental to the bauplan of the order and to the evolution and functional morphology of spider reproductive systems. Indeed, after two centuries of comparative research on spider reproduction, the presence of a single spermophor and embolus on each of a male spider’s two pedipalps remains a central tenet of evolutionary arachnology. Our findings challenge this premise, and reveal a remarkable twin intromittent organ sperm transfer system in a lineage of Australian palpimanoid spiders, characterized by a bifurcate spermophor and the presence of two efferent ducts leading to a pair of embolic sclerites on each pedipalp. This is the first time such a remarkable conformation has been observed in any group of arachnids with direct sperm transfer, complicating our understanding of palpal sclerite homologies, and challenging ideas about the evolution of spider genitalia.
Abstract
Improving our sparse knowledge of the mating and reproductive behaviour of white rhinoceros (Ceratotherium simum Burchell, 1817) is essential for the effective conservation of this iconic species. By combining morphological, physiological and habitat data with paternity assignments of 104 known mother–offspring pairs collected over a period of 13 years, we provide the most comprehensive analysis of the mating system in this species. We show that while the overall mating system was promiscuous, and both males and females produced more offspring when mating with several partners, half of all females with multiple offspring were monogamous. Additionally, we find that mating and reproductive success varied significantly among territorial males in two independent sets of males. In females, however, variation in the mating and the reproductive success was not larger than expected by random demographic fluctuations. Horn size, testosterone metabolite concentration, territory size, habitat openness and the volume of preferred food within the territory did not seem to influence male mating or reproductive success. Moreover, there was no sign of inbreeding avoidance: females tended to mate more frequently with closely related males, and one daughter produced a progeny with her father. The lack of inbreeding avoidance, in combination with the skew in male reproductive success, the partial monogamy in females and the territorial‐based mating system, jeopardizes the already low genetic variation in the species. Considering that the majority of populations are restricted to fenced reserves and private farms, we recommend taking preventive measures that aim to reduce inbreeding in white rhinoceros. A video abstract can be viewed here.
Haematophagous leeches express a broad variety of secretory proteins in their salivary glands, among them are hirudins and hirudin-like factors. Here, we describe the identification, molecular and initial functional characterization of Tandem-Hirudin (TH), a novel salivary gland derived factor identified in the Asian medicinal leech, Hirudinaria manillensis. In contrast to the typical structure of hirudins, TH comprises two globular domains arranged in a tandem-like orientation and lacks the elongated C-terminal tail. Similar structures of thrombin inhibitors have so far been identified only in kissing bugs and ticks. Expression of TH was performed in both cell-based and cell-free bacterial systems. A subsequent functional characterization revealed no evidence for a thrombin-inhibitory potency of TH.
Background
Hibernation allows species to conserve energy and thereby bridge unfavorable environmental conditions. At the same time, hibernation imposes substantial ecological and physiological costs. Understanding how hibernation timing differs within and between species can provide insights into the underlying drivers of this trade-off. However, this requires individualized long-term data that are often unavailable. Here, we used automatic monitoring techniques and a reproducible analysis pipeline to assess the individualized hibernation phenology of two sympatric bat species. Our study is based on data of more than 1100 RFID-tagged Daubenton’s bats (Myotis daubentonii) and Natterer’s bats (Myotis nattereri) collected over seven years at a hibernaculum in Germany. We used linear mixed models to analyze species-, sex- and age-specific differences in entrance, emergence and duration of the longest continuous period spent in the hibernaculum.
Results
Overall, Daubenton’s bats entered the hibernaculum earlier and emerged later than Natterer’s bats, resulting in a nearly twice as long hibernation duration. In both species, adult females entered earlier and emerged from hibernation later than adult males. Hibernation duration was shorter for juveniles than adults with the exception of adult male Natterer’s bats whose hibernation duration was shortest of all classes. Finally, hibernation timing differed among years, but yearly variations in entrance and emergence timing were not equally shifted in both species.
Conclusions
Our results suggest that even in sympatric species, and across sex and age classes, hibernation timing may be differentially affected by environmental conditions. This highlights the necessity of using individualized information when studying the impact of changing environments on hibernation phenology.