590 Tiere (Zoologie)
Refine
Year of publication
Document Type
- Doctoral Thesis (50)
Has Fulltext
- yes (50)
Is part of the Bibliography
- no (50)
Keywords
- Evolution (5)
- Phylogenie (4)
- Anpassung (3)
- Fledermäuse (3)
- Klimawandel (3)
- Nervensystem (3)
- Ökologie (3)
- Adaptation (2)
- Aedes (2)
- Bicyclus anynana (2)
Institute
In drei verschiedenen Teilanalysen wurden Erkenntnisse über die Wirksamkeit von Interventionsmaßnahmen gegen das Vorkommen und die Verbreitung von ESBL/AmpC-bildenden E. coli in der Hühnermast gewonnen. Literaturdaten und praktische Laborergebnisse, die teilweise selbst erhoben wurden, flossen in ein mathematisches Modell ein, um die Auswirkungen von Haltungsparametern und konkreten Interventionsmaßnahmen prädiktiv berechnen zu können. Die zusammengefassten Ergebnisse zeigen einen Einfluss der Maßnahmen „Competitive Exclusion“, „Reinigung und Desinfektion“ sowie den Haltungsparametern „Rasse“, „geringe Besatzdichte“ und „erhöhte Einstreumenge“ auf das Vorkommen von bestimmten ESBL/AmpC-bildenden E. coli. Zusätzlich zu den Einzelmaßnahmen wurden im Modell mehrere Kombinationen getestet, wobei zwei unterschiedlichen Szenarien verwendet wurden, entweder der Stall oder die Eintagsküken waren zu Beginn der Mastperiode positiv. Diese Kombinationen ergaben eine deutliche Reduktion der resistenten E. coli in den infizierten Tieren, in deren Ausscheidungen und in der Einstreu. In diesem Zusammenhang wären Daten aus tierexperimentellen Studien zu kombinierten Maßnahmen interessant. Weitere wissenschaftliche Ergebnisse könnten zu einem optimierten Modell beitragen, damit es die realen Bedingungen besser widerspiegelt. Zu einer weiteren Präzisierung könnte zum Beispiel die dezidierte mathematische Berechnung des Wachstums von resistenten E. coli in den unterschiedlichen Teilen des Gastrointestinaltrakts des Huhns und in der Einstreu führen, unter Berücksichtigung von pH-Wert und Temperatur. Ungeachtet dessen bietet die vorliegende Version des Modells eine nützliche Unterstützung bei der Vorhersage der Auswirkung unterschiedlicher Maßnahmen auf das Auftreten und die Verbreitung von ESBL/AmpC-bildenden E. coli in Masthuhnbetrieben. Diese Ergebnisse können zu einer umfassenden Quantitativen mikrobiologischen Risikobewertung (QMRA) beitragen, mittels derer die Effizienz von Risikominderungsmaßnahmen in der gesamten Broilerproduktionskette, von der Brüterei und Aufzucht über die Mast, Schlachtung, Verarbeitung und den Einzelhandel bis hin zum Verzehr - from farm to fork, bestimmt werden kann.
Species are the basic units of evolution and biodiversity, and the process of speciation has been one of the most important questions in biology. The evolution of species with common descent is considered to be mainly driven by natural and sexual selection. The material basis and mechanical cause of organismic evolution were recognized during the formation of the modern synthesis of the evolutionary theory in the early 20th century, providing the framework for speciation studies. During this period, the biological species concept was developed in the frame of population genetics, putting emphasis on the reproductive isolation between populations. The phylogenetic species concept developed in the 1980s, on the other hand, does not make any particular assumption about evolutionary or speciation processes. It defines species via their unique combination of character states which are compatible with phylogenetic practices. However, the aforementioned two species concepts are difficult to apply in alpha-taxonomy, where newly discovered species are largely described by the morphological (typological) species concept for practical reasons. Nevertheless, the description of morphological species provides the basis for further assessments of species delimitation via other species concepts and approaches. One of the tools for assisting the identification and discovery of animal species is DNA barcoding, which uses a standard region of mitochondrial DNA sequence as a universal DNA barcode. However, its assumption of intraspecific genetic distances being smaller than interspecific genetic distances does not always hold. Species-level poly-/paraphyly is prevalent due to the discrepancy between the phylogenies of mitochondrial DNA and species. This suggests that the application of DNA barcodes must be combined with an integrative taxonomic approach. Beside the application as a tool for assisting species identification, the information from mitochondrial DNA sequences opens up a window for looking into the complex history of species.
Sexual selection is a potential mechanism driving the evolution of species. It favors traits that increase mating probability and mating success. It can result from intrasexual competition, female preference or sexual conflict. However, previous comparative studies using the degree of sexual dimorphism as a proxy for the strength of sexual selection have yielded inconsistent results as to the relationship between sexual selection and species richness. A possible cause of the inferred low association are factors other than sexual selection, which can also lead to the evolution of sexual dimorphism, such as selection for increased female fecundity. In order to assess the effect of sexual selection on speciation, the lability and evolvability of traits need to be studied that are clearly under sexual selection.
The aim of this thesis is to improve the knowledge about dwarf spider (Erigoninae, Linyphiidae) diversity and taxonomy, and to assess the evolutionary patterns of dimorphic traits that are under sexual selection. I focused on the abundant and diverse male prosomal modifications in dwarf spiders that are linked to the transfer of secretions from the male to the female during courtship and mating (gustatory courtship). This approach explores the process of speciation and the role of sexual selection on species diversification. I described new erigonine species and revised the classification of known species based on phylogenetic analyses. I also applied X-ray micro-computed tomography (micro-CT) to investigate the distribution and evolutionary pattern of the gustatory glands to tease apart the evolution of prosomal shape and glandular equipment.
This cumulative thesis consists of three publications:
Publication 1: This publication aimed at contributing to the knowledge of erigonine diversity. The genus Shaanxinus previously contained only two species from China. I collected dwarf spiders from multiple locations in Taiwan from above-ground vegetations with a seldom applied collecting method. Inspection of the collected material resulted in the discovery of 13 Shaanxinus species. An additional species from Vietnam was described from a museum collection. I provided a revision of the genus Shaanxinus. A phylogenetic analysis using morphological characters was conducted for determining the possible generic synamomorphies. I also reconstructed the glandular distribution associated with male prosomal modifications, as well as the detailed structure of a male secondary sexual organ (pedipalp) by micro-CT. Furthermore, I conducted phylogenetic analyses based on sequences from two mitochondrial and one nuclear loci, and assessed the efficacy of different criteria in species identification using DNA barcoding. Distinction of morphologically similar species have been assisted by molecular data. The species level poly-/paraphyly found in mitochondrial DNA sequences caused the low efficacy of many distance- and tree-based species identification methods, while the nearest neighbor method showed high identification success. The non-monophyly is likely caused by instances of interspecific hybridization and recent parapatric speciation. The genus Shaanxinus thus lend itself as an ideal group for congeneric phylogeographic studies addressing the interactions between closely related species. Published in: Lin, S.-W., Lopardo, L., Haase, M. & Uhl, G. 2019. Taxonomic revision of the dwarf spider genus Shaanxinus Tanasevitch, 2006 (Araneae, Linyphiidae, Erigoninae), with new species from Taiwan and Vietnam. Organism Diversity & Evolution, 19, 211-276.
Publication 2: Sexually dimorphic prosomal modifications that are related to gustatory courtship occur in many dwarf spider species. These features evolved in the context of sexual selection, which has a potential effect on species diversification. In contrast to many
erigonine genera which present little variability in male prosomal traits, the genus Oedothorax presents higher diversity in male prosomal structures among species not only in the position and shapes of the modifications, but also in the degree of modification, ranging from absent to highly elaborated. This genus thus lends itself as a suitable target group for studying the effect of gustatory-courtship-related traits on species diversification. I conducted a revision of the 82 species previously belonging to this genus. Based on the result of a phylogenetic analysis, this genus was re-delimited with 10 species as Oedothorax sensu stricto, while taxonomic decisions were made for other species including synonymization with species from other genera and transferring species to other existing and newly defined genera. 25 species were deemed as “Oedothorax” incertae sedis. The reconstruction of character state evolution suggested multiple origins of specific prosomal modification types. Convergent evolution of these traits among different lineages suggests that sexual selection has played an important role in the species diversification of dwarf spiders. Published in: Lin, S.-W., Lopardo, L. & Uhl, G. 2021. Evolution of nuptial-gift-related male prosomal structures: taxonomic revision and cladistic analysis of the genus Oedothorax (Araneae: Linyphiidae: Erigoninae). Zoological Journal of the Linnean Society, XX, 1-168.
Publication 3: Although sexually dimorphic traits have inspired the concept of sexual selection as the driving force of their evolution, they might also have evolved due to other ecological factors. These factors include the sexual signal adaptation to the environment as well as sexual differences in ecological relations and parental investment. In contrast, the gustatory courtship in dwarf spiders is associated with sexually dimorphic male prosomal modifications, which have clearly evolved in the context of sexual selection. Multiple origins of various external prosomal modifications have been shown in erigonine phylogeny, but the evolutionary pattern of the associated glands has not been investigated. Our phylogenetic analysis incorporated the characters related to the glandular distribution in the male prosoma as well as the external shapes yielded from X-ray micro-computed-tomography showed a single origin of gland among the investigated erigonine taxa. The internal anatomy revealed previously undetected trait lability in attachments of muscles to the cuticular structures, as well as the presence/absence and differences in glandular distribution even in species without external modification. Our finding further supports that erigonine male prosomal traits are under divergent selection, and corroborates the argument that erigonines are a suitable group for investigating the effect of sexual selection on speciation. Published in: Lin, S.-W., Lopardo, L. & Uhl, G. 2021. Diversification through gustatory courtship: an X‑ray micro‑computed tomography study on dwarf spiders. Frontiers in Zoology, 18: 51.
The results of this thesis corroborate the importance of applying phylogenetic methods and an integrative approach in the description of new species, as well as in revising taxa which might not be monophyletic. Overall, the studies contributed to a more comprehensive knowledge about erigonine species diversity, phylogeny and the possible diversifying effect of sexual selection on male traits associated with gustatory courtship.
Bats are special: although they have a small body size, bats are extremely long-lived and have a low annual reproductive output, which puts them at the ‘slow’ end of the slow-fast continuum of mammalian life-histories. Species typically respond to climate change by genetic adaptation, range shifts or phenotypic plasticity. However, limited dispersal behavior in many bat species and long generation times make it very likely, that adaptive responses in bats are rather driven by phenotypic plasticity than by genetic adaptation or range shifts. Changing weather patterns, a higher frequency of extreme weather events and overall rising temperatures, caused by climate change, will impact phenology, energy supply and energy expenditure. In species where adult survival largely shapes population dynamics, it is thus of crucial importance to understand how climate change affects individual fitness and fitness relevant traits by altering behavior and development.
In my study, I investigated how weather impacts behavior, fitness and fitness relevant traits in free ranging Natterer’s bats from two geographical regions (south vs. north) in Germany. In the Nature Park Nossentiner/Schwinzer Heide (northern region, NSH), long-term data for investigations on population dynamics are partially collected by hibernation counts. Although counting hibernating bats is a regularly applied method, it is still unclear to which degree human visits in the hibernaculum trigger energy consuming arousals and thus increase energy expenditure. Thus, I first investigated if hibernation counts potentially threaten winter survival by assessing the number of energy consuming arousals of hibernating Natterer’s bats (Myotis nattereri) and two other bat species (Pipistrellus spp., Plecotus auritus) using thermal imaging. Additionally, I used light barriers in the hibernacula to investigate the relative impact of winter temperatures and human visits on flight activity of hibernating bats. Secondly, I investigated effects on survival and reproduction during summer by analyzing capture-mark-recapture data from summer roosts. Data from summer roosts have been collected since 2011 in Würzburg (WB, south) and 1990 in the Nature Park (NSH, north). Based on these data, I analyzed the effect of intrinsic (e.g. age) and extrinsic(e.g. different weather parameters) factors on individual survival probability and reproductive success. I further focused on the question if individual body size is a fitness relevant trait in Natterer’s bats and how body size of young bats is affected by summer temperatures.
During hibernation, ambient temperatures were the most important driver for bat activity and were positively correlated with the number of flight passes in the light barrier, suggesting that bats can exploit foraging opportunities more frequently during warm weather bouts. Monitoring caused only a small number of arousals and only a slight increase in activity, which was less severe on warmer days, when activity was generally higher. Thus, I propose that benefits of hibernation counts outweigh the costs of human presence in the hibernaculum and unlikely threaten winter survival in hibernating bats.
In spring, increased precipitation during a short time window strongly reduced the probability of successful reproduction in first-year females (females that returned from first hibernation, FY). In terms of timing, this sensitive period comprises the implantation or early pregnancy, a time before substantial investment into embryo development. Moreover, I identified a positive correlation between a large body size and reproductive success in FY females. Given the evidence that suitable weather conditions during early life support juvenile growth and thus a large body size, my findings suggest that reproduction may be condition dependent in young females. Reproductive success of older females was not affected by either weather or individual parameters. This suggests that older and experienced females can better deal with adverse conditions.
To examine if beneficial weather conditions are linked to a large body size, I investigated the effect of ambient temperatures during the growing season on body size. I found that higher ambient temperatures during summer led to larger individuals, however, only in the northern population. In the on average colder North, warmer summers may benefit juvenile growth by reducing thermoregulatory costs and increasing prey abundance, whereas in the general warmer South, this effect might not be visible or relevant. When I analyzed the link between body size and survival, I revealed that larger adult females have higher survival rates. Given the fact, that a large body size is a response to beneficial early life conditions, this demonstrates the impact of early life conditions on long lasting fitness effects.
The results of my research lead to the assumption that warmer ambient temperatures have positive effects on Natterer’s bats, both during winter and summer. However, increased activity in response to rising winter temperatures, as expected under climate change scenarios, could be a serious thread for hibernating bats, if food availability does not increase in the same amount as bat activity. During summer, warmer temperatures may have positive effects on juvenile development in northern regions, but this effect could be negative in more southern regions by exceeding heat tolerance and resulting in water stress. This research highlights, that investigating periods of weather sensitivity on a finer time scale and also in a spatial context is of crucial importance to gain a better understanding for mechanisms leading to the impacts of weather on fitness.
As the effects of anthropogenic climate change become more pronounced, it is critical to understand if and how species can persist in novel environments. Range-expanding species provide a natural experiment to study this topic: by studying the factors contributing to successful colonization of new habitats, we can gain insight into what influences organisms’ adaptive potential. The wasp spider, Argiope bruennichi, has expanded its range from warm, oceanic and Mediterranean climate zones (populations in this region are referred to as “ancestral” or “core”) into a new thermal niche, the continental climate of the Baltic States and Scandinavia (referred to as “expanding” or “edge”) within the last century. Past work demonstrated that the expanding populations are European in origin, but are more diverse than the ancestral populations, due to genetic admixture. This discovery led to the following questions, which are investigated in this dissertation: (i) Was the successful colonization of colder, more continental northern climates due to phenotypic plasticity or genetic adaptation? (ii) If A. bruennichi’s establishment of northern latitudes can be attributed to genetic adaptation, did selection act on standing genetic variation, on genetic variation introduced via admixture/introgression, on specific genomic regions, or on novel mutations? (iii) Is there a role of the microbiome in the A. bruennichi range expansion?
In Chapter 1, we assembled a chromosome-level genome for the species: the first such high-quality genome for a spider, which we made use of as a resource to provide the genomic context of single nucleotide polymorphisms in our primary study on genetic adaptation and phenotypic plasticity (Chapter 3). The genome assembly also opened the door to many new projects, such as the study presented in Chapter 2. In Chapter 2, the chromosome-level resolution of our assembly allowed us to identify the sex chromosomes in A. bruennichi. Due to the X1X20 sex chromosome system, where males have one copy of two X chromosomes, and females have two copies, the X chromosomes have a lower effective population size, and lower recombination rate, than autosomes. These characteristics give rise to the theoretical prediction of increased evolutionary rates in sex chromosomes. Knowing the identity of the sex chromosomes in our A. bruennichi genome assembly will allow us to test if there is stronger differentiation between populations on the X chromosomes.
Chapter 3 represents the central study of this dissertation. We performed a reciprocal transplant common garden experiment to assess plasticity and adaptation in cold tolerance traits, using spiderlings from the core of the range in France, and the edge of the range in Estonia. We combined this with data on clinal variation in adult phenotypes (body size, pigmentation, and fecundity) and genotypes in a transect across the European range. This study revealed a strong signature of genetic adaptation for increased cold tolerance in edge populations, and clear genetic differentiation of ancestral and expanding populations over a very short geographic distance, despite gene flow. We provide genome-wide evidence for adaptive introgression, and conclude that the A. bruennichi range
expansion was enabled by adaptive introgression, but has reached a poleward range limit.
Interactions with microbes shape all aspects of eukaryotic life. Endosymbiotic bacteria have been shown to alter the thermal tolerance of arthropod hosts, and influence dispersal behavior in spiders. With this background, in Chapter 4, we asked whether the microbiome might play a role in the rapid range expansion of A. bruennichi. We characterized the microbiome in various dissected tissues of spiders from two populations. Although we found no obvious differences between populations or tissues, this study yielded the discovery of a novel, dominant, vertically transmitted symbiont with astoundingly low similarity to all other sequenced bacteria. Since that discovery, we have found evidence of the unknown symbiont in A. bruennichi populations across the Palearctic (unpublished data), making it relatively unlikely to play a role in the range expansion.
By studying the establishment and subsequent differentiation of core versus edge populations of A. bruennichi following range expansion, we were able to gain insight into the evolutionary and ecological processes that allowed this species to successfully cope with novel environments. The rapidity with which local adaptation arose in A. bruennichi suggests that evolutionary adaptation to novel environments is possible over short time periods. However, this may only be possible in species with sufficient standing genetic variation, or with genetic variation introduced via admixture, as in A. bruennichi, which has important implications for our understanding of species responses in the face of ongoing global climate change.
Under the influence of human activities, increased climate variability induces changes in
multiple marine environments. Especially vulnerable are the coastal ecosystems where organisms
must cope with constant extreme changes of environmental drivers, such as temperature, salinity, pH,
and oxygen content. In coastal areas, brachyuran crabs are important animals that have a high impact
on ecosystem functioning and serve as a link in food webs and pelagic-benthic coupling. Larval stages
of crabs are crucial for population persistence and dispersal. They are generally more vulnerable to
changes of environmental drivers and failure to adapt to new conditions may result in population
collapse. To analyse the effects of multiple environmental drivers on larval performance and to
elucidate interspecific and intraspecific difference, this project examined larval performance in the
European shore crab Carcinus maenas. In this study, larvae of C. maenas from three native
populations (Cádiz: Cádiz Bay, Helgoland: North Sea, Kerteminde: Baltic Sea) were reared in a
factorial design consisting of different temperature (15-24 °C) and salinity treatments (20, 25, 32.5
PSU). Results demonstrated how descriptors of larval performance (growth, physiological, and
developmental rates, and survival) were affected by combined environmental drivers. Larval
responses to temperature and salinity showed contrasting patterns and differed among native
populations originating from distant or contrasting habitats, as well as within the populations. The
highest overall performance was recorded in the Cádiz population, while the Kerteminde population
had the lowest performance in most of tested traits. The interactive effects of multiple drivers differed
among the populations. In the Cádiz and Helgoland populations, higher temperatures mitigated the
effect of lower salinity while the Kerteminde population showed a maladaptive response when
exposed to lower salinity. Differences in performance showed better locally adapted populations (e.g.
Cádiz) that could acclimate faster, have better adaptive mechanisms or stronger dispersive abilities.
Because of their wider tolerance to increased temperature and decreased salinity, interactive effects
in particular populations may favour some populations in a changing climate, especially in coastal
habitats. Variation in larval performance showed complex interactions in larval performance and
highlighted the necessity to quantify inter-population responses to climate-driven environmental
change where responses of species should not be generalised. This study emphasizes the need for
inclusion of multiple traits, drivers, and populations in experimental studies to properly characterize
performance of marine coastal animals.
Midges are small mosquitoes that can transmit pathogens to susceptible hosts through their blood-sucking act. They are known as biological vectors that can transmit the bluetongue virus (BTV) and the Schmallenberg virus (SBV) to ruminants, among others. Various vector control measures can be used to curtail the spread of the virus during an epidemic. However, for effective vector measures, it is essential to have profound knowledge of the role of biting midges as vectors, as well as their biology and phenology. For several years, midges were not in the focus of research and there are still considerable gaps in knowledge. Therefore, the present work examines various aspects of biting midges of the genus Culicoides, whose function as vectors of the Schmallenberg virus was already proven at the beginning of the project.
The aim of the first part of this work was to determine the percentage of infected midges in various German areas in order to determine the influence of Culicoides midges within the virus epidemic. For this purpose, samples, collected during 2011 and 2012 as part of monitoring projects, were analysed. Additionally, in early 2013, various farms in southern and eastern regions of Germany, where SBV was considered to be largely absent, were equipped with UV traps. The small number of virus-positive samples did not allow a more precise assessment of the viral spread in culicoid midges. Instead, it revealed the importance to conduct targeted samplings of its vectors during an acute outbreak. Additionally, the presented results and statements made by several animal owners, gave reason to believe, that SBV must have affected the southern and eastern parts of Germany earlier than actually assumed. This would consequently have led to an increased immunity in host animals, which provides a reasonable explanation for the low positive values and is in agrement with the statements made by various farmers.
The second part of this work identifies the conditions and surrounding factors under which acute SBV diseases emerged in ruminants in the cold winter months of 2012/2013. After the diagnosis of several acute SBV infections of sheep in a sheep pen in Mecklenburg-Western Pomerania, culicoid midge activity could be proven. This demonstrates that, suitable conditions for its vectors given, an infection of SBV can also take place during wintertime. A more detailed analysis of the surrounding conditions revealed, that the outdoor temperatures during infection were consistently at values of at least 5-9 ° C for several consecutive days, which enabled the flight and blood-sucking activity of the midges within
the shelter.
Midge activity during wintertime represents a crucial component in understanding how the virus can outlast the cold season. A constant midge presence could lead to a low but permanent infection rate throughout the cold months, enabling a recurrence of the pathogen the following year. Instead, a longer vector-free timeperiod would point to other mechanisms that allow the virus to re-occur in Germany on a yearly basis. Thus, the acute cases of SBV infections in sheep rose the question of critical threshold temperatures, representing the beginning of midge activity. The investigation of several stables sheltering cattle, horse or sheep addressed potential differences between indoor and outdoor activity and whether the type of host animal has an influence on the beginning of the flight. In the third part of this work, a long vector-free period and several differences in the onset of midge activity between different types of host animals could be detected. It could also be illustrated that the progression of the flight began differently depending on the present type of host animal/type of stable. For all cattle stables and the sheep barn the first midge activity was measured indoors, whereas for horses, culicoid midges were found to become active either at the same time or almost simultaneously inside and outside the animal shelters. This suggests that the horse stables do not represent good breeding sites for midges, which might be attributed to husbandry practices. In addition, it was possible to determine specific threshold temperatures for the different types of host animals and for various midge species. Altogether, the late beginning of flight, measured at the beginning of March, was surprising. This raises more questions of alternative mechanisms enabling the virus to outlast the winter months. The documentation of species-specific threshold temperatures can be a useful tool f.i. within automated large stables to keep indoor temperatures under the threshold value in order to postpone the onset of culicoid activity of various vector species. This may help to prevent virus transmissions during winter or to evoke a delay in spring, making it more difficult for the virus to overwinter.
To be able to start instant defense measures during an ongoing virus epidemic, which is transmitted by Culicoides midges, reducing the ground-living midge larvae offers a promising option during the warm season. For targeted vector control measures, it is important to know the breeding sites of culicoid midge species. Therefore, four agriculturally used biotopes were sampled and compared to four biotopes of a forest-dominated area. The results clearly show that meadows per se are not suitable breeding habitats for Culicoides
spp. Only the influence of livestock animals induces their potential as developmental sites. The various biotopes of the forest-dominated region were less subject to anthropogenic influences. Although fewer individual midges were found here, it displayed a higher biodiversity than the agricultural habitats. These results demonstrate once more the potential of forests in regards to the preservation of biodiversity. In Particular, the alder on fen site revealed most midge species and also the highest number of collected specimens among the studied biotopes. That illustrates the high impact of this specific humid type of habitat in respect to species diversity and the need of its perpetuation.
As part of this work, new breeding sites for a variety of culicoid species were identified and assigned to the usually rather short profiles of known Culicoides species. For one part, previous observations of chosen substrates could be consolidated. Furthermore, new breeding substrates were identified. Additionally, information of abiotic factors such as ph-value, soil moisture or organic compound of all sampled breeding substrates obtained from a soil analysis, extended the knowledge about the species-specific choice of breeding habitats and their characteristical traits. The additional knowledge about potential breeding substrates and their soil factors might be useful for future epidemiological modelling approaches. It can also raise the effectiveness and accuracy of targeted vector control measurements during an epidemic outbreak. Therefore, it may indirectly contribute to the preservation of endangered rare species. However, there is still an enormous need for more research before this goal can be fully achieved.
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.
In Germany, basic data on the biology, ecology and distribution of rare mosquito species are insufficiently recorded leading to knowledge gaps, for example regarding their vector potential. The introduction of new mosquito species and of the pathogens they transmit has increased the risk of diseases previously uncommon in Germany. These circumstances have led to increased efforts within the past 10 years to better understand the spatio-temporal occurrence and underlying habitat binding of mosquito species and to predict their future distribution, particularly with regard to the changing climatic conditions and changing landscape. A reliable morphological and genetic identification was lacking for several native mosquito species, which forms the basis for any robust monitoring within mosquito surveillance programs or insect conservation projects.
The aim of this thesis was to gain detailed knowledge on the current spatial and temporal occurrence, the habitat binding, and morphological and genetic features with regard to species identification for the non-native species Aedes albopictus (Skuse, 1895), the native species of the Aedes Annulipes Group, and the native and rare species Aedes refiki Medschid, 1928, Culex martinii Medschid, 1930 and Culiseta ochroptera (Peus, 1935).
The thesis compares the suitability of the local climate for the persistence of the species Aedes albopictus sporadically observed in Jena (Thuringia) from 2015 to 2018 with two populations in southern Germany. The focus was on the analysis of extreme winter temperatures and the duration below selected temperature thresholds. In addition to critical temperature conditions, aquatic habitat conditions were of importance. The results of this study suggest that the population could become established in the long term.
Through the monitoring conducted for this thesis, the very rare mosquito species Aedes refiki, Culex martinii in Thuringia and Culiseta ochroptera were rediscovered at several sites in northern and eastern Germany. It was possible to add new information on habitat binding, distribution and abundance for the considered mosquito species. The survival of these rare native mosquito species depends on the preservation of a few remaining habitats. In addition, it can be assumed that these species will become even rarer with future climate change in Germany and, therefore, should be considered endangered. In contrast, other mosquito species could benefit from an increase in average temperatures or precipitation in individual cases.
Due to the contribution to species identification, difficulties in the morphological and genetic identification of selected mosquito species native to Germany could be dispelled. Three forms each were assigned to the known morphological variants of Aedes refiki and Culiseta ochroptera and their peculiarities were described, as well as a new character for species identification was highlighted in the case of Culiseta ochroptera. Generated CO1 mtDNA sequences provide the first DNA-barcodes of Aedes refiki and Culex martinii for Germany.
In five native mosquito species of the Aedes Annulipes Group, twenty types of aberrant tarsal claws were illustrated and described in their morphology. Morphological peculiarities and an asymmetrical occurrence of the aberrant claw types were observed and possible causes for their development were discussed. Together with the development of a basic blueprint of mosquito tarsal claws, the results opened another field of research for the taxonomy, developmental biology and aquatic ecology of arthropods.
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.
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.