Research Projects

Research Projects

RESPONSE entails 12 individual research projects, which are organised within two research clusters. Cluster A focusses on local in situ responses to environmental change (i.e. plasticity and genetic adaptation), as moving to new habitats might be difficult for many species in modern fragmented landscapes. Therefore, phenotypic adjustment is expected to play a crucial role for the future prospects of any given species. Consequently, we will quantify the genetic and plastic potential and the relative importance of both in six model taxa. Cluster B is dedicated to understanding the factors associated with successfully colonising new habitats. Given that genetic adaptation may not be fast enough to track current global change and that plastic responses are predicted to incur costs, the ability to move to and colonise new habitats will be of great importance for many species. While range shifts in response to recent climate change have been widely documented, the factors promoting dispersing to and especially establishing in new habitats are only poorly understood, as are the ecological and evolutionary consequences of range dynamics.

Cluster A - In situ responses: Plasticity and genetic capacities

A1 - Phenotypic plasticity in the New Zealand mud snail

A secret of success: Phenotypic plasticity as prerequisite for being a generalist

Gerlien Verhaegen & Martin Haase

State of the art: During phases of global change generalist species are predicted to have a higher survival chance than specialists. However, what constitutes a generalist, in particular with regard to the relative importance of phenotypic plasticity and genetic adaptation, is little understood. This question will be addressed here in the ovoviviparous New Zealand mud snail Potamopyrgus antipodarum occupying a wide range of fresh and brackish water habitats and exhibiting an extreme morphological variation. In this species, triploid, (almost) all-female parthenogenetic lineages have evolved repeatedly and successfully invaded other continents, emphasizing the species’ adaptive potential. The broad ecological niche has possibly been realized due to a high degree of phenotypic plasticity. Gastropod shell shape and size have been already related to environmental factors including current velocity and temperature. Therefore, this project focuses on the adaptive value of shell shape and size as well as on osmotolerance in P. antipodarum, disentangling phenotypic and genetic adaptation and the influence of the reproductive mode thereon.

Working hypotheses and work plan: We will relate adult shell size and shape of P. antipodarum, which has finite growth, as well as the number of brooded embryos to habitat characteristics in its native range. We will control for confounding factors including phylogeny, geography, ploidy, parasitism, predation risk, and population density. In a similar fashion, we will analyze parthenogenetic populations established in Europe assuming that clonal strains accumulate mutations and thus adapt differentially. These analyses will form the basis for the selection of differentially adapted populations for common garden experiments aiming at measuring reaction norms, estimating heritabilities through parent-offspring regressions, thus disentangling genetic from plastic effects. Snails will be exposed to different flow velocities, temperatures, and salinities and effects on shell size, shape, growth rate, fecundity and survival will be recorded. We expect sexual populations to show a higher degree of plasticity, and, assuming costs of phenotypic plasticity, trade-offs with fecundity.

Thesis topic: Variable shell morphology as key for colonizing a wide spectrum of habitats?

A2 - Osmotolerance in the snail Theodoxus fluviatilis

Osmotolerance in Theodoxus fluviatilis

Amanda Wiesenthal, Christian Müller & Jan-Peter Hildebrandt

State of the art: Molecular phylogeographic studies have revealed that Theodoxus fluviatilis (Gastropoda: Neritidae) has formed regional subgroups (lineages) in northern Germany which seem to occur either in freshwater or in brackish water (Mol Ecol (2005) 14: 4323; Mol Phylogenet Evol (2007) 42: 373). These lineages were assigned to different subspecies, although individuals from freshwater and brackish water habitats are indistinguishable with respect to shell size and patterning (J Conchol (2004) 38: 305) and are genetically uniform with respect to mitochondrial DNA markers (Mol Ecol (2005) 14: 4323; Mol Phylogenet Evol (2007) 42: 373). In their responses to salinity changes, however, snails from the two lineages do differ (Biol Zentralbl (1960) 5: 585; Estuar Coast Mar Sci (1978) 6: 409; J Comp Physiol B (2010) 180: 337). The higher salinity tolerance of the brackish water lineage enables these animals to thrive in areas of the Baltic Sea with salinities up to 18 ‰. These animals seem to avoid freshwater habitats such as lakes and streams connected to the Baltic Sea (J Conchol (2004) 38: 305). It is currently unclear whether high salinity tolerance is an original trait of this species (having broad reaction norms that may have been shifted by local adaptation) or a derived feature which was newly developed during re-colonization of the Baltic Sea from freshwater habitats after the last glaciation period. Using biochemical tests, we have confirmed that Theodoxus individuals from brackish water are much more capable of regulating cell volume by the accumulation of free amino acids in foot muscle tissue than individuals from freshwater. Comparisons of protein expression patterns of soluble foot muscle proteins using 2D-gel electrophoresis and silver staining revealed that some proteins seem to be regulated according to the physiological condition of the animal (phenotypic plasticity) while others are differentially expressed in a lineage-specific manner (indicating genetic differentiation).

Working hypotheses and work plan: Using animals from the two lineages collected at three different sites each, we will aim to answer the following questions: (1) Is there a shift in reaction norms in animals to different osmolalities due to plastic responses in biochemical traits? Test: Determine osmotolerance ranges of individuals which have been kept at different salinities for up to 8 weeks. (2) Is the range of osmotolerance inheritable? Test: Breeding of animals of one population over at least 2 generations under controlled conditions and testing the osmotolerance ranges (survival, sugar and amino acid accumulation) in parents and their offspring. (3) Are there qualitative or quantitative differences in mRNA / protein expression in animals of the two lineages which provide evidence for genetic differentiation? Test: N-terminal sequencing of proteins isolated from 2D-gels, comparison with data from transcriptome analyses, Western blotting, in situ-hybridisation for analyzing tissue-specific expression and function.

Thesis topic: Limits of physiological acclimation to salinity stress in Theodoxus.

A3 - Life history responses of bats to climate change

Life history responses of bats to climate change

Christine Reusch & Gerald Kerth

State of the art: Recent studies have reported decreasing body size as a response to climate change in various taxa, a phenomenon termed ‘global shrinking’ (Nat. Clim. Change 1: 401). As body size and fecundity are often positively correlated, shrinking body size may lead to higher extinction risks. Interestingly, in a few species increasing body size in response to climate change has been observed, which may occur in species needing warm weather for growth, such as bats. However, the fitness implications of such poorly documented trends are currently unclear. Bats are particularly interesting for studying the influence of climate change on body size and its relations to individual fitness, because they are long-lived, of high conservation concern, and show a number of behaviours that allow them to cope with weather variation, e.g. social thermoregulation, torpor, and roost switching.

Working hypotheses and work plan: This project will study the morphological and behavioural responses to variation in weather conditions in three bat species. For Myotis bechsteinii, long-term field data and detailed genetic data are available for several populations, where all bats are individually marked with RFID-tags. We also possess comparable long-term data for a number of populations of Myotis nattereri and Plecotus auritus. In this project we will test whether (1) ambient temperature affects body size directly and indirectly via food availability (2) social factors such as group size also influence body size via social thermoregulation, and thus can buffer the effects of the weather and (3) body size has an effect on the fitness, in particular during extreme weather events. The study will be carried out in collaboration with the group of Prof. Dr. F. Schweitzer, ETH Zurich (social network analyses) and Dr. A. Scheuerlein, MPIDR Rostock (demography). The work plan includes (1) analyses of the long-term data on morphology, demography, behaviour, genetic composition of populations, and individual fitness, (2) experimental manipulations of roost quality to quantify behavioural responses to changing temperatures (3) use of parent-offspring regressions and more advanced methods such as “animal models” to estimate the heritability of body size (4) comparisons of species-specific responses among different study sites.

Thesis topic: Costs, benefits and constraints of responses to recent climate change in bats.

A4 - Coping with extreme environments in a butterfly

Physiological defence mechanisms to cope with extreme environments

Franziska Günter, Michaël Beaulieu & Klaus Fischer

State of the art: Given that extreme weather events are ecologically more important than average conditions, investigating responses to and reaction norms including sudden extreme conditions holds great potential for our ability to forecast the fate of populations. This is because a population’s limit to persist may be exceeded during extreme events, such that the organisms’ immediate defence mechanisms play an important role in population survival. Here, we will investigate plastic and genetic variation in physiological defence mechanisms (i.e. antioxidant defences, heat shock response, immune response and desiccation resistance) in replicated populations of the butterfly Pieris napi. In particular, we will explore the species’ capacity to buffer detrimental effects of extreme weather events such as heat waves, and how different defence mechanisms interact with each other when coping with extreme events. We will pay special attention to oxidative stress (i.e. an imbalance between the production of free radicals and antioxidant defences), which has received very little attention in the context of climate change.

Working hypotheses and work plan: We will use replicated populations of P. napi from warm and cold environments to establish (1) the relative ecological importance of, (2) reaction norms for and (3) interrelations between different physiological defence mechanisms. We have chosen P. napi as it forms morphological distinct populations in cold environments and is easy to breed in captivity. Specifically, we will test the following hypotheses: (1) plastic physiological responses will be disrupted under extreme environmental conditions, causing non-linear reaction norms; (2) physiological defences are traded-off against each other; (3) repeated exposure to stressful conditions induces a hormetic response (i.e. individuals pre-exposed to a specific stressor should show increased performance when exposed again); (4) structural lipid composition of cell membranes and inducible (antioxidant enzyme) defences are both important to buffer negative effects of heat-induced oxidative stress (in cooperation with Prof. J. Ellers; VU Amsterdam). Parent-offspring regressions will be used to estimate the heritability of 1-2 defence mechanism(s) of high relevance. In that case, females will be given time to lay eggs before being exposed to stressful conditions, after which they are sacrificed for physiological measurements.

Thesis topic: Costs, limits and the mechanistic basis of physiological defences.

A5 - Responses of forest trees to environmental change

Disturbance and adaptive potential – How fast can long-lived plants react to environmental change?

David Würth, Pascal Eusemann & Martin Schnittler

State of the art: Within the life span of long-living trees the local climate may change to a degree that would not allow the very same individuals to establish again today. Therefore, the individuals performing best today may not necessarily be those that will perform best tomorrow, but once established, they still produce most of the offspring. This allows for two contrasting adaptation scenarios: (1) In undisturbed habitats with dense stands intraspecific competition is high. Plants with ‘modern’ genotypes well adapted to current conditions suffer from competition with established plants adapted to past conditions, decreasing the speed of adaptation. (2) In contrast, disturbed or novel habitats (e.g. northwards or upslope of current treelines) may provide unoccupied space for seedling recruitment. Selection in trees acts mainly during establishment. In these environments, selection for modern genotypes should therefore act faster than under stable conditions. This will be tested in white spruce (Picea glauca) which forms monospecific forest and treeline stands in the North American subarctic, a region of pronounced warming during the last decades. To study of the applicability of these processes over species and ecosystem boundaries, we will also study silver fir (Abies alba), which occurs in a mosaic of old-growth and frequently disturbed stands in Germany. In contrast to the temperature-limited Picea forests, Abies is limited by interspecific competition in these environments.

Working hypotheses and work plan: We will compare populations representing undisturbed (closed canopy sites) and disturbed conditions (disturbed or arctic treeline sites). Both adult trees and established seedlings (>30 cm tall) will be mapped, measured and genotyped. As a first step, the relationship between individual performance (annual increment, photosynthetic rate, fungal parasite load) and fitness (seed set and number of established offspring) will be investigated for the adult cohort. We will then measure performance of the offspring (yearly height growth, photosynthetic rate, fungal parasite load) to study whether those parents performing best also produce the most and best performing offspring. All plants will be genotyped and pedigrees reconstructed using microsatellite markers. This will allow calculation of heritability in traits related to fitness and estimation of genetic and plastic components of trait expression. Additionally, trait plasticity under natural conditions will be assessed using naturally occurring clones.

Thesis topic: Comparative individual performance in adult and offspring cohorts of Abies alba and Picea glauca.

A6 - Phenotypic plasticity and genetic adaptation in F. sylvatica

Potentials and limits of phenotypic plasticity and genetic adaptation in Fagus sylvatica

Lena Muffler, Andrey Malyshev & Jürgen Kreyling

State of the art: Fagus sylvatica (European Beech) is the dominant natural forest tree in Central Europe and thrives under a wide range of climatic and environmental conditions. Yet, F. sylvatica is expected to suffer from climate change due to a low seed dispersal capacity and drought sensitivity. Phenotypic plasticity, however, within and among populations is high and can be expected to buffer against climate change in situ. Local adaptation to different climates has been demonstrated in common garden experiments. Limits of phenotypic plasticity and consequences of selection by local climate on genetic constitution, however, are unclear. Such knowledge will ultimately allow for improved projections of range shifts, and provide guidance for long-term sustainable forest management.

Working hypotheses and work plan: We will quantify phenotypic plasticity and genetic adaptation at the recruitment stage of F. sylvatica using individuals that germinated and established under local climates different from their origin. Failure to establish will indicate limits of plasticity (and adaptation). We will study the importance of phenotypic plasticity of mothers (quantified by tree ring analyses) and their offspring under various climates, allowing estimating heritabilities and additionally genetic variation using neutral markers (microsatellites). We will focus on establishment and juvenile growth as traits of crucial importance for fitness. Seeds from several mother trees, originating from different populations covering major climatic gradients over the species’ range, will be exposed to the full range of ambient conditions at all places of origin (full reciprocal transplantation) and most interestingly also to conditions well beyond the current range. In addition, the importance of selection through drought stress on establishment will be quantified for individuals with or without drought stress during establishment. Establishment and survival will further be tested in climate chambers for causal interpretation of field data.

Thesis topic: Phenotypic plasticity and its heritability in recruitment cohorts of F. sylvatica under various climates.

Cluster B - Colonising new habitats: Factors for success

B1 - Persist or disperse: Protists in unstable environments

Persist or disperse – who does best in unstable environments?

Mathilde Borg Dahl, Thomas Hoppe & Martin Schnittler

State of the art: All mechanisms to cope with changing environments, plastic responses, genetic adaptation and dispersal in search for new habitats infer costs. Which of these constitutes a suitable way for free living protists will be investigated for plasmodial slime molds (myxomycetes). These organisms inhabit soils with unicellular, haploid amoebae but form minute fruit bodies dispersing meiospores (Soil. Biol. Biochem. 43: 2237). Only well adapted genotypes can support plasmodia and are able to fruit (FEMS Microbiol. Ecol. 31: 103). We will investigate how environmental stability (time of contiguous snow cover over elevational transects) determines survival in nivicolous myxomycetes (Meriderma spp.). Only a long-lasting, stable snow cover allows amoebae to multiply at a constant temperature of 0-0.5°C and finally fruit. Beside sexual spore formation, culture studies and a model for habitat colonization (Mycol. Res. 112: 697) mount evidence for the existence of a second, apomictic life cycle resulting in fruit bodies with automictic spores (Mycosphere 4: 233).

Working hypotheses and work plan: Field work will be conducted in the northern Caucasus and in the German Alps (Fungal Divers 59: 109). Molecular work will include sequencing of marker genes (SSU, EF1a, PLoS One e22872, e35359). In addition, we will attempt barcoding using environmental PCR of soil samples and subsequent Illumina sequencing to assess genetic diversity in fruiting and non-fruiting populations. Amoebae will be isolated from soil or raised from spores to test reaction norms regarding temperature and freeze/thaw cycles. We will assess plastic/genetic components of trait variation by comparing trait expression (spore number, diameter, ornamentation and hydrophobicity) in fructifications within/between genotypes. Environmental sensitivity of selection will be estimated as change in phenotypic traits of fructifications and compared with length of contiguous winter snow cover as main environmental parameter (revealed by data loggers). Comparing genotypes in several mountain ranges we will test if local genetic adaptation or phenotypic plasticity and rapid dispersal is the best strategy for these organisms.

Thesis topic: Genetic diversity, reproductive options and gene flow in the genus Meriderma.

B2 - Range dynamics of Picea glauca

Range dynamics of Picea glauca

Mario Trouillier, Marieke van der Maaten-Theunissen & Martin Wilmking

State of the art: Treelines have been a classical ecological example to study the ability of species to colonise new habitats (Ecology 15: 80) or to retreat under unfavourable conditions (Ecology 86: 1687). Recent climate change is expected to lead to substantial treeline advance at leading edge populations, and dieback of trailing edge populations, though the role of increasing climate extremes is unresolved (PNAS 106: 19723). Limiting factors for tree growth in northern regions might shift from cold to drought (Nature 405: 668), possibly influenced by decreasing seasonality (Nat. Clim. Change 3: 581). Picea glauca is the main northern and elevational treeline species in Alaska, also occupying the dry edge of coniferous tree growth in Interior Alaska (Can. J. For. Res. 43: 331). Both range edges are undergoing massive environmental change (projected to intensify in the future) with associated range dynamics (Can. J. For. Res. 40: 1197), most likely not limited by dispersal (Ecology 86: 1687).

Working hypotheses and work plan: To increase the understanding on how P. glauca range edges can cope with rapidly changing mean and extreme climatic conditions in Alaska, the role of phenotypic plasticity and in situ adaptation on the advance and dieback of this tree species will be investigated. Therefore, the history of climatic stress (especially the effects of extreme events) and phenotypic variability in growth and wood anatomy of the mother trees will be quantified by tree-ring analyses (in cooperation with Dr. U. Sass-Klaassen; Wageningen University) and related to phenotypic variability in growth and wood anatomy of the offspring, identified via genetic analyses.

Thesis topic: Role of phenotypic plasticity in range dynamics of Picea glauca under rapidly changing climatic conditions in Alaska.

B3 - Environmental stress, neurogenesis and colonisation in crustaceans

Effects of environmental stress on neurogenesis in crustacean larvae

Franziska Spitzner, Andy Sombke & Steffen Harzsch

State of the art: Climate change already has a major impact on marine ecosystems including plankton communities (Prog. Oceanograph. 81: 207). In particular semi-enclosed seas (e.g. the Baltic Sea) will be increasingly affected by rising surface temperatures and decreasing salinity due to a higher river runoff (J. Exp. Mar. Biol. Ecol. 400: 52). Decapod crustaceans may be particularly sensitive to such changes, owing to their complex life cycle including a pelagic larval and a benthic juvenile-adult stage. Here, larval survival critically depends on the ability to respond appropriately to chemical, mechanosensory and visual cues to control tidal transport and onshore recruitment (Invert. Reprod. Dev. 49: 175). Larval settlement is of utmost importance for colonisation and population survival, relying on e.g. odour identification indicating preferred habitats and the presence of conspecifics (Mar. Freshwater Behav. Physiol. 39: 269). Hence, the ability to sense environmental cues is an ecologically important trait intimately associated with fitness. However, larval growth and bioenergetics in decapod larvae are strongly affected by thermal and osmotic stress (Invert. Reprod. Dev. 33: 159). While concomitant effects on growth patterns are well understood, knowledge on the effects of abiotic stress on the development of specific, energy-demanding organs such as the nervous system and hence on behavioural performance is lacking. Therefore, we will here explore the effect of abiotic stress on the development of the larval olfactory system and olfactory-guided behaviour.

Working hypotheses and work plan: Current climate change may expose crustacean planktonic larvae to increasing abiotic stress (see above). We hypothesise that (1) thermal and salinity stress will negatively affect neurogenesis and thereby larval behavioural performance, and that (2) negative effects will differ depending on the respective species’ ability to tolerate challenging environmental conditions. To this end, we will study the effects on osmotic and thermal stress on the development of the olfactory system in larvae of six European decapod crustaceans, which are known to differ in their stress tolerance (Aquat. Biol. 21: 249). Investigations will include (1) in vivo incorporation of an s-phase specific mitosis marker to quantify neurogenesis; (2) immunohistochemistry against neuropeptides and confocal laser-scan microscopy to analyse the formation of neuronal networks within the central olfactory pathway, (3) scanning and transmission electron microscopy to analyse the ontogeny of the chemosensory organs; (4) bioessays to analyse larval responses and sensitivity ranges to environmental stimuli. A major part of the breeding experiments will be carried out at the “Biologische Anstalt Helgoland”, a marine biological station on the island of Helgoland/North Sea in cooperation with Dr. Gabriela Torres and Dr. Luis Gimenez (Bangor, Wales).

Thesis topic: Effects of abiotic stress on neurogenesis in the developing brain of crustacean larvae.

B4 - "Range-shift syndromes" in butterflies

"Range-shift syndromes" in butterflies: a comparison between core and edge populations

Elisabeth Reim, Isabell Karl & Klaus Fischer

State of the art: Current global change has caused range shifts in a plethora of species, and butterflies have become important model organisms for such range dynamics. For populations trying to colonise new habitats their potential to persist or even thrive in edge populations is of crucial importance. Edge populations are usually not a random subset of the genotypes found in central populations but are biased towards genotypes showing enhanced dispersal ability and shorter life cycles. The consequences of the concomitant increased energy allocation to such genetically-based ‘range-shift’ syndromes are hitherto poorly understood. Especially in flying ectotherms, which disperse by highly energy-demanding flight, these syndromes are expected to generate trade-offs with other energy-demanding functions, e.g. the immune response, which may feedback on the ability to persist. Investigating potential interactions with disease resistance is particularly interesting as increased heat stress resistance may be traded off against immune function, and because the distribution and prevalence of infectious diseases are predicted to change with global warming. Here we will investigate factors affecting dispersal ability in replicated populations of the currently northward expanding butterfly Lycaena tityrus, paying special attention to range-shift syndromes and associated trade-offs. Thus, we will investigate differences in and constraints on dispersal ability at the environmental and genetic level.

Working hypotheses and work plan: The replicated populations will originate from recently established edge (Estonia, Russia) and core (Germany) populations of L. tityrus. Using well-established protocols we will investigate whether proxies of dispersal ability are affected by genetic (population comparisons) and environmental (temperature, resource availability) factors, and whether they are traded off against other energy demanding functions (immune response, reproduction). Dispersal ability will be measured at the morphological (e.g. wing loading, aspect ratio), physiological (fat reserves) and behavioural (dispersal) level under laboratory and semi-natural conditions. We will test the following hypotheses: (1) dispersal ability is enhanced in edge populations; (2) core and edge populations show heritable variation in dispersal ability (parent-offspring regression); (3) dispersal ability is associated with intrinsic (morphology, physiology) and external (abiotic conditions, resource availability) factors; (4) immune response and reproduction are traded off against genetically based range-shift syndromes, with trade-offs being more pronounced in edge populations (in collaboration with Prof. R. Stoks, Univ. Leuven); (5) newly established edge populations show a reduced genetic diversity at neutral loci (microsatellites) but not at loci important for local adaptation (e.g. PGI, HSP).

Thesis topic: Factors affecting dispersal ability in a butterfly.

B5 - Dispersal in a range-expanding spider

Dispersal strategies: Phenotypic plasticity and genetic adaptation within and between populations of a range-expanding spider

N.N. & Gabriele Uhl

State of the art: Global climate change often results in poleward range expansions. A new and promising model species for rapid range expansion is the orb-weaving spider Argiope bruennichi that moved from the Mediterranean region into continental climates and up to Scandinavia and Finland within less than 100 years. Consequently, its current distribution covers very different climates and environments. The rapid northward expansion of A. bruennichi was probably facilitated by admixture of formerly isolated lineages through global warming, resulting in an introgression of Asian alleles into the central European genepool (Mol. Ecol. 22: 2232). Taking advantage of the available population genetic and phylogeographic data as well as a fully sequenced genome and a solid understanding of the biology of the species, we will investigate adaptive responses in dispersal behaviour within and between populations along a latitudinal gradient. Dispersal behaviour is of crucial importance for rapid range expansion as well as for establishing populations.

Working hypotheses and work plan: We will investigate dispersal strategies of populations from the northern range limit (Sweden, Finland), the original range (Mediterranean), and genetically distinct island populations from the Azores to determine causes and consequences of variability in dispersal behaviour. We hypothesise that (1) populations differ in the propensity to disperse with northern range populations showing the strongest and island populations the weakest propensity, (2) behavioural plasticity is strongest in northern populations since the shorter period for growth requires immediate responses to local conditions. In breeding experiments under varied conditions, we will determine the degree of genetic and phenotypic variation. We will further test the hypotheses that (3) dispersal probability is affected by resource availability, population density (response to chemical cues), the future risk of inbreeding, and sex, that (4) dispersing phenotypes are of better condition and have higher competitive ability than philopatric phenotypes and that (5) maternal effects partly determine dispersal behaviour through selective provisioning of eggs. The project is conducted in close collaboration with Prof. J. Schneider (Univ. Hamburg, Germany) and Prof. D. Bonte (Univ. Gent, Belgium).

Thesis topic: Environmental and genetic effects on dispersal behaviour in a range expanding spider.

B6 - Range expansion in lesser horseshoe bats

Ecological drivers and genetic consequences of range expansion in lesser horseshoe bats

Lisa Lehnen, Sébastien Puechmaille & Gerald Kerth

State of the art: The European vertebrate fauna is highly dynamic due to both historical climatic variation and anthropogenic pressures. For some species, such as the Palearctic bat species Rhinolophus hipposideros, regressions and advances are quite well documented. In Western Europe, this species underwent a drastic population decline in the mid 20th century, with a pronounced southward receding of its distribution edge. Since several decades, however, re-colonization of former habitat via dispersal has been observed for colonies in central Germany, which are among the northernmost ones on the European continent. A species' dispersal capacity and thus, its ability to track environmental changes by range shift are expected to be a major determinant of extinction risk (Science 313: 789). Elucidating dispersal ability and mechanisms in the lesser horseshoe bat and identifying parameters determining these is necessary to test the explanatory power of current models which predict a northward progression of this species during the next decades (Global Change Biol. 16: 561). We investigate colony formation via dispersal in expanding R. hipposideros colonies in central Germany, study trade-offs / associations between dispersal and life history traits, and elucidate factors influencing dispersal, paying special attention to social and environmental factors.

Working hypotheses and work plan: Droppings will be collected from selected colonies in central Germany in three consecutive years. Bat DNA from this material will be genotyped at 9 microsatellite loci to estimate realized dispersal and further demographic parameters such as population size, reproduction rate, and vitals (survival / mortality). These will reveal a great deal about the lesser horseshoe bat's potential for life strategy adaptation to habitat availability – an important prerequisite for taking advantage of global warming rendering higher latitudes climatically suitable. Furthermore, ecological and environmental factors of interest are tested for their influence on R. hipposideros dispersal and genetic structure with a landscape resistance modeling approach. Specifically, we will investigate (1) How new maternity colonies are formed, (2) If expanding colonies in central Germany exhibit an adaptation in their life strategy to benefit from habitat availability, resulting in increased reproduction and dispersal rates, (3) Which ecological and environmental factors facilitate or impede dispersal in the lesser horseshoe bat. The study is carried out in collaboration with local conservationists in central Germany (fmthuer.de) and Dr. E. Petit, INRA (Rennes, France).

Thesis topic: Spatio-temporal variation in dispersal in R. hipposideros and implications for fitness and genetic diversity.