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

Lisa Männer & 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. Invasive species are ideal models to dissect adaptation into its constituent mechanisms as they have successfully colonized novel habitats. We will work with 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, polyploid, all-female parthenogenetic lineages have evolved repeatedly and these have invaded other continents, emphasising the species’ adaptive potential. The clonal reproduction of these lineages is an ideal prerequisite to disentangle genetic from non-genetic effects. Our most recent genetically controlled analyses based on geometric morphometrics confirm the adaptive value of shell shape and size, hence these traits will be focus of our investigations. Analyzing the influence of environmental parameters on shell morphology in field and laboratory experiments we aim at estimating the heritability of these traits and quantify the relative contribution of genetic and non-genetic factors contributing to adaptation.

Working hypotheses and work plan: Using European as well as native lineages, heritability of shell traits will be estimated by common garden experiments in the laboratory as well as conducting reciprocal transplant experiments between different habitat types. We will relate two measures of fitness, viz. shell morphology (survival) as well as brood size (fecundity) to habitat characteristics. The morphological analyses will be conducted in the framework of geometric morphometrics. Genetic and plastic effects will be disentangled measuring reaction norms and estimating heritabilities through parent-offspring regressions (sexual lineages) as well as comparisons of between and within lineage variabilities (clones). In addition, we will screen native natural populations for signatures of selection comparing samples from different habitat types using genotyping by sequencing approaches against the background of the reference genome currently established by our external collaboration partner Maurine Neiman (Univ. Iowa).

Thesis topic: Quantifying genetic and environmental effects in adaptation to different habitats in the morphologically variable New Zealand mud snail Potamopyrgus antipodarum

A2 - Osmotolerance in the snail Theodoxus fluviatilis

Osmotolerance in Theodoxus fluviatilis

N.N., Christian Müller & Jan-Peter Hildebrandt

State of the art: Phylogeographic studies have revealed that Theodoxus fluviatilis (Gastropoda: Neritidae) has formed regional subgroups in northern Germany which seem to occur either in freshwater or in brackish water (Mol Ecol 14: 4323; Mol Phylogenet Evol 42: 373). Individuals from freshwater and brackish water habitats are not easily distinguishable by parameters as shell size or patterning (J Conchol 38: 305) and are genetically uniform with respect to mitochondrial DNA markers (Mol Ecol 14: 4323; Mol Phylogenet Evol 42: 373). In their responses to salinity changes, however, snails from the two lineages do differ (Biol Zentralbl 79: 585; Estuar Coast Mar Sci 6: 409; J Comp Physiol B 180: 337). Moreover, freshwater animals show different survival rates in experiments with different medium salinities than those from brackish water. Theodoxus uses compatible osmolytes (amino acids) to balance cell volume during changes in medium salinity. We could recently show, however, that amino acid biochemistry is obviously not a strictly limiting factor for survival during osmotic stress. This indicates that other factors (inorganic ions, ion transporters, skin water permeability) are significantly contributing. Future studies are planned to identify factors limiting or allowing survival under unfavourable medium salinities and enable us to estimate which of them may be determined genetically or may respond plastically to changes in environmental conditions.

Working hypotheses and work plan: We want to qualitatively and quantitatively investigate the contributions of inorganic and organic osmolytes, their trans-membrane transporters and the water permeability of the integument as limiting factors for survival of snails under osmotic stress. Comparison of protein expression patterns in tissue extracts (gel-based and gel-free; cooperation with the proteome analysis group headed by Prof. Riedel, A4) in conjunction with the analysis of qualitative or quantitative differences in mRNA patterns (we have sequenced the Theodoxus transcriptome during the initial period of this project) in animals of the two origins may reveal possible markers for processes or mechanisms of osmotolerance in this species.

Thesis topic: Molecular markers for osmotolerance in the euryhaline snail Theodoxus fluviatilis

A3 - Life history responses of bats to climate change

Life history responses of bats to climate change

Carolin Mundinger, Caroline Schöner & Gerald Kerth           

State of the art: Bats are long-lived, of high conservation concern and show behaviours as well as physiological responses, such as roost switching, social thermoregulation, and torpor that allow them to cope with weather variation. Torpor, which is characterized by a reduction in body temperature and metabolic rate, allows bats to save energy during adverse conditions when food availability is low. At the same time, frequent use of torpor during the breeding season can slow down the growth of the juveniles. During the first A3 project (2015-2018), evidence for possible cost-benefit trade-offs has been found for behavioural responses to changing environmental conditions such as the timing of the departure from the hibernaculum in spring. Early departure increases the mortality risk in some years but may be beneficial in others when the food availability is high during warm weather conditions in late winter/early spring. Moreover, we in an associated project we could show that in female Myotis bechsteinii large body size is correlated with decreasing survival in our study populations, for which we have a data set spanning 25 years. This finding provides strong evidence for a negative correlation between body size and fitness in this species. In combination with their longevity and low annual reproductive output, cost-benefit trade-offs and possible constraints on phenotypic plasticity make bats highly interesting for studying the potential impact of climate change on individual fitness and ultimately population persistence.

Working hypotheses and work plan: Building upon the findings of the previous projects our next research goals are to assess to which extent the observed fitness-relevant responses are caused by genetic factors or phenotypic plasticity. The existing field and genetic data of up to 25 years will be combined with new (experimental) data to quantify the influence of weather conditions on the behaviour, morphology, reproductive success and survival of RFID-tagged bats belonging to four species (M. bechsteinii, M. daubentonii, M. nattereri, Plecotus auritus). Multigenerational family pedigrees in combination with animal models will be used to measure the heritability of body size and other potential fitness relevant traits such as departure timing from the hibernaculum or age at first reproduction. We will also perform roost selection experiments and manipulations of the micro-climate of roosts to test for the influence of roosting temperatures on body size of the juveniles growing up in these roosts. This will allow us to get further insights into the effect of global warming on the body size of our study species. The relative importance of larger body size (in response to increasing temperature), behaviour (e.g. roost choice/hibernation departure timing), and social factors (e.g. position in the social network) on fitness (survival, reproductive success) will be investigated together with the local partner M. Beaulieu and external partners Jutta Gampe/Alex Scheuerlein (MPI for Demographic Research in Rostock) and Melanie Dammhahn (Univ. Potsdam).

Thesis topics: Relative importance of plastic and genetic responses to weather conditions in long-lived bats.

A4: The lichen microbiome and its role in adaptation to climate change

Maria Grimm, Prof. Katharina Riedel & Dr. Jörg Bernhard, Institute of Microbiology

State of the art: Symbiotic communities such as lichens represent a frequent and successful lifestyle on earth. Lichens consist of a heterotrophic fungus (mycobiont) and an autotrophic photosynthetic partner (photobiont), generally green algae and/or cyanobacteria. Within the last decade, bacterial communities were identified as stable, specific, and structurally integrated partners of the classical lichen symbiosis. Recently, the application of integrated culture-independent meta-omics approaches has added valuable knowledge to the lichen symbiosis, not only about the taxa involved in lichen interactions, but also about their contributed functions (Front. Microbiol. 17:180). There is now strong evidence that the diverse microbiota contribute multiple aspects to the symbiotic system, including health, growth, and fitness (ISME J. 9:412, J Proteome Res. 16:2160, Microbiome 5:82). We thus believe, that the strategy of functional diversification supports longevity of lichens under extreme conditions and that the highly versatile microbial community enables the lichen holobiont to rapidly adapt to a changing environment, i.e. due to global warming. Our project complements RESPONSE by investigating phylogenetic and functional changes of the lichen symbiotic community induced by different climate conditions. 

Working hypotheses and work plan: This project will decipher molecular mechanisms of the model lichen
L. pulmonaria during adaptation to changing climate conditions, especially temperature and moisture
. Preliminary analyses, comparing two L. pulmonaria sources grown in Austria (Steiermark) and Germany (Darß) suggest the presence of a partly stable microbiome, however, also indicated significant differences between the proteomes of the two lichen microbiomes in contrast to the rather stable fungal and algal protein profiles (J Proteome Res. 16:2160). We hypothesize, that especially changes in the composition and functionality its microbiome enable the lichen holobiont to cope with environmental changes. We will extend our current knowledge by (1) a comprehensive phenotypic characterization and metaproteomics analyses of samples collected from different geographical sites, i.e. Austria, North Germany, Denmark and Sweden, during different seasons, (2) the analyses, integration, and visualization of local climate, phenotypic and omics-data by in house designed bioinformatics tools, and (3) the verification of the omics-data by in situ analyses of laboratory-cultured L. pulmonaria subjected to different temperature and moisture conditions in collaboration with Prof. Schnittler (A5).

Thesis topic: A metaproteomics approach to decipher the impact of the L. pulmonaria microbiome on its adaptation to climate change.

A5 - Responses of forest trees to environmental change

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

Melanie Zacharias, Manuela Bog & Martin Schnittler

State of the art: White spruce (Picea glauca) is the main northern and elevational treeline species in Alaska, forming often monospecific stands. The genetic differentiation of populations as measured with neutral markers is low, which hints towards effective long-distance gene flow mediated by pollen. This may help trees to adapt to novel environments but may as well cause maladaptation (Ecol. Lett. 15: 378). Although global warming may disrupt gene flow via decreasing synchrony in flower time (Ecol. Ecol. 7: 5754-5765), adaptation-related traits may respond better to climate gradients (Glob. Chang. Biol. 19: 1645). In addition, variation in trait expression and overall tree performance seems to be very high, which makes sense since climate may change during the lifetime of a tree (PLoS Biology 8: e1000357). Therefore, individuals performing well in former times may currently not sire most of the offspring, and this contradiction may be more pronounced in fast-changing environments, e.g., treelines. Since selection in trees acts mainly during establishment (Theor. Popul. Biol. 42: 172), and site conditions are crucial for recruitment success, such trends can only be demonstrated with large sample sizes. Identifying fitness-related traits and estimating their heritability is therefore crucial to measure the speed of adaptation.

Working hypotheses and work plan: We  will assess genetic differentiation of populations based on an SNP assay, and relate these patterns a) to trait expression (radial growth as provided by project B2, and morphology of needles) and b) to the results of a microsatellite-based parentage analysis to assess reproductive output of trees. Existing field and genetic data from three paired plots across Alaska (over 1000 trees) will be enlarged by a SNP assay. Heritability of measured traits will be estimated by relations to SNP patterns, parent-offspring regression and clone/non-clone comparisons. The project is carried out in close cooperation with project B2 (Prof. Wilmking), where the focus is on germinating and growing seedlings of known mother trees under controlled conditions. Within the frame of a structured PhD school, field work in a highly motivated team and the opportunity to write joint publications will help you to avoid the pitfalls of a “lonely PhD” and make the best out of your skills.

Thesis topic: Heritability and plasticity of radial growth and morphological traits in White Spruce.

A6 - Phenotypic plasticity and genetic adaptation in F. sylvatica

Potentials and limits of phenotypic plasticity and genetic adaptation in F. sylvatica

Jonas Schmeddes, Andrey Malyshev & Jürgen Kreyling

State of the art: Dominant temperate-zone tree species such as Fagus sylvatica thrive under a wide range of climatic and environmental conditions (Ann. Forest Sci. 63: 355). Yet, F. sylvatica is expected to suffer from climate change due to a low seed dispersal capacity and drought sensitivity (Glob. Change Biol. 12: 2163; Trees 21: 1). Phenotypic plasticity within and among populations, however, is high (Agr. Forest. Meteorol. 180: 76; Silvae Genet. 44: 343) and can be expected to buffer against climate change in situ. Furthermore, F. sylvatica shows high genetic diversity within populations, fairly low within-region differentiation but distinct genetic variation over larger scales across Europe (New Phytol. 171: 199). 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 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 and genetic variance of mothers and their offspring under various climates, allowing to estimate heritabilities and additionally genetic variation using neutral markers (microsatellites), and for selected samples from different origins, SNPs. We will focus on establishment and juvenile growth as traits of crucial importance for fitness, stomata density and SLA as stress-related traits and leaf area as morphological trait. Seeds from several mother trees, originating from different populations covering major climatic gradients over the species’ range, have been 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 and frost stress on establishment are quantified for individuals with or without drought or frost stress during establishment. The obtained estimates of plasticity, heritability, and genetic adaptation will be used to constrain hybrid species distribution models (e.g. Ecol. Lett. 19: 1468).

Thesis topic: The role of genetic adaptation, phenotypic plasticity and its heritability for projecting the distribution of F. sylvatica.

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?

Jan Woyzichovski, Nikki Dagamac & Martin Schnittler

State of the art: Myxomycetes (slime molds) are traditionally a subject of mycology, but belong to the Amoebozoa (protists) and play a crucial role in soil ecosystems (PLoS ONE e2527) as predators of bacteria. One ecological guild lives in alpine environments: nivicolous myxomycetes require a long-lasting, stable snow cover that allows amoebae to multiply and finally form colonies of fruit bodies 1-3 mm in size which release airborne spores (Naturwiss. 96: 147). Species are distinguished by morphological characters of the fructifications (Fungal Divers. 59: 109) and seem to inhabit all mountain ranges of the northern hemisphere (Mycologia 101: 1). Environmental stability (time of contiguous snow cover over elevational transects) should favour sporocarp formation, but amoebal populations can persist as well in non-favourable environments (Sci. Rep. 6: 19068).

Working hypotheses and work plan: Working on elevational transects in different mountain ranges of Europe and Western North America, we will relate spore features from collections of fruit bodies to occurrence of fructifications and/or soil amoebae as revealed by metagenomics. Accessions from the field will be sequenced by multiple independent markers, alternatively an SNP assay for true genotyping will be developed (associated PhD student). Spore features (size, ornamentation) will be assessed from light and electron microscopic images, using image processing scripts in imageJ. With experiments aiming to determine terminal velocity and hydrophobicity of spores we will relate spore features to dispersal abilities. Heritability of these traits will be assessed by clone (sporocarps of one colony) / non-clone (different colonies) comparisons.

These features will be compared with the elevational (within a transect) and geographical (different mountain ranges) distribution of species to test the hypothesis that species with abundant fruiting and highly dispersible spores will have the largest range and/or are most frequently recovered in soil samples.

Thesis topic: Relative importance spore traits for dispersal in fruit body-forming protists (Myxomycetes).

B2 - Range dynamics of Picea glauca

Range dynamics of Picea glauca

Timo Pampuch, Tobias Scharnweber & Martin Wilmking

State of the art: Treelines have been a classical ecological example to study the ability of species to colonize 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 die-back of trailing edge populations, though the role of increasing climate extremes and local adaptation is unresolved. 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 with associated range dynamics. But how well are local populations adapted to expected climatic extremes and gradual shifts in climate? Here we will investigate the role of phenotypic plasticity and in-situ adaptation on the advance and dieback of P. glauca range edges under rapidly changing mean and extreme climatic conditions in Alaska.

Working hypotheses and work plan: This project will assess how gradual climate shifts and extreme climatic conditions drive fitness-relevant traits (e.g. radial tree growth or water transport capacity of the stem) and how tree growth variability in these traits is caused by genetic factors or phenotypic plasticity. We will also test, whether the relative impact of genetic versus plastic responses depends on local conditions and possible local adaptation. Existing field and genetic data from three study sites across Alaska (over 1000 trees) will be combined with new (field and experimental) data collected during the project period. We will germinate and grow spruce seedlings from all field sites in common garden experiments in Greifswald, submitting them to expected climatic extremes such as drought or frost (cooperation with Prof. Kreyling). In close cooperation with project A5 (Prof. Schnittler), we will employ suitable methods, such as parent-offspring regression and clone/non-clone comparisons, of Alaskan field data to approach the quantification of heritability in fitness relevant traits of Picea glauca. And, last but not least, we will have some fun in the field and lab.

Thesis topic: Treeline dynamics of Picea glauca in Alaska - Is in-situ adaptation of edge populations a prerequisite for range expansion?

B3 - Environmental stress, neurogenesis and colonisation in crustaceans

Effects of environmental stress on neurogenesis in crustacean larvae

Zoran Šargač, Jakob Krieger & Steffen Harzsch

State of the art: Early developmental stages of most marine coastal organisms are essential for population persistence and dispersal. They are mostly planktonic and thus more vulnerable to fluctuating environmental conditions in the water column. Climate change already has a major impact on marine ecosystems including plankton communities. In particular, semi-enclosed seas will be increasingly affected by rising surface temperatures but also by decreasing salinities due to a higher river run-off. Planktonic larvae of decapod crustaceans for example must cope simultaneously with the variation of combined thermal and osmotic stress due to extreme weather events. Therefore, one area of research on population persistence and range expansion in crustaceans addresses the capacity of crustacean larvae to tolerate combined thermal and osmotic stress. We have previously quantified the combined effects of abiotic stress on various aspects of larval quality in the common shore crab Carcinus maenas. These experimental studies were carried out at the Alfred Wegener Institute at the island of Helgoland using animals from the local population of Carcinus maenas.

Working hypotheses and work plan:Multi-population comparisons can be instrumental to understand local adaptation and phenotypic plasticity in order to predict pending ecosystem changes. We want to know if larvae of the common shore crab Carcinus maenas taken from mothers from different populations across its native range (Bergen/Norway, Bangor/Wales, Kiel/Baltic Sea, Spain) display different levels of resistance to environmental stress (temperature and salinity). The project advertised here will be carried out in collaboration with Dr. Gabriela Torres (Alfred Wegener Institute at Helgoland) and Dr. Luis Gimenez (School of Ocean Sciences, Bangor University, Wales). The expression of key metabolic enzymes, proteins related to ion regulation and heat shock proteins will be analysed in larvae from these populations. In behavioral essays, we will test the acute thermal tolerance of the larvae at hatching. In a common garden experiment, larvae from the four populations will be reared under a previously tested regime of combined abiotic thermal and osmotic stress at the Alfred Wegener Institute at Helgoland. Building on the expertise from the previous project, in these larvae, we will measure larval survival, developmental length, dry weight, and elemental composition. We will also measure a previously identified morphological key trait, the amount of lipid inclusions in resorptive cells (R cells) of the digestive epithelium in the midgut gland as the central metabolic organ. We will also perform immunohistochemistry against NaKATPase in the larval transport epithelia.

Thesis topic: Global change influences population persistence and drives range expansion of marine species: exploring plasticity in the tolerance against environmental stress.

B4 - "Range-shift syndromes" in butterflies

Effects of early thermal conditions on dispersal-related traits across a latitudinal gradient

Anaïs Degut, Mikaël Beaulieu & Peter Michalik

State of the art: In holometabolous insects, adult characteristics are largely determined during their early stages of life (eggs, larvae). Accordingly, we recently found that Pieris napi butterflies exposed to a high temperature as pre-adults showed smaller wings, higher wing loading, and a change in the ratio between their forewing and hindwing when adults. Interestingly, these effects varied with the latitudinal origin of butterflies. This suggests that early thermal conditions may determine the ability of adult butterflies to disperse, and that these effects vary between populations. However, such changes in flight ability are likely to generate trade-offs with other energy-demanding functions (e.g. physiology, thermal tolerance), which may ultimately limit the dispersal potential of butterflies.

Working hypotheses and work plan: Here, we will investigate plastic and genetic variation in the morphology (wing characteristics, pigmentation, body mass, thorax musculature), physiology (oxidative status, immune response, lipid composition, cuticle desiccation resistance, pigmentation) and behaviour (flight characteristics) of the butterfly Pieris napi exposed to different thermal regimes as pre-adults. We will use replicated populations of P. napi across a latitudinal gradient across Europe (i.e. from warm to cold environments) to establish the interrelations between these parameters and to examine their heritability under variable environmental conditions. Specifically, we will test the following hypotheses: (1) morphological, physiological and behavioural characteristics are inter-related; (2) the effects of early thermal conditions on the morphology, the physiology and the behaviour of butterflies vary with the latitudinal origin of butterflies, (3) flight ability determined by early thermal conditions is negatively related to the thermal tolerance of adults, (4) heritability of the investigated traits is not significantly affected by thermal conditions (parent-offspring regressions will be used to estimate heritability). Most of the project will be conducted in captivity but will also involve some fieldwork. This project will be conducted in collaboration with research partners at the Universities of Greifswald, Koblenz-Landau, Ljubliana and Amsterdam.

Thesis topic: Genetic and environmental effects on the morphology, physiology and behaviour of a European butterfly.

B5 - Dispersal in a range-expanding spider

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

Monica Sheffer & 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 in 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). Based on the available population genetic and phylogeographic data, and on our solid understanding of the biology of the species, we study the morphological, behavioural and genetic responses to variation in environmental conditions in A. bruennichi. To this aim, we compare populations from the range expanding front of the distribution (Baltic countries) with those of the central area in Southern France, and complement the picture by adding island populations from the Azores. The project contributes to the overall aim of the RTG by pinpointing factors of success in species that colonise new habitats.

Working hypotheses and work plan: We will investigate variation between populations from the northern range limit (Estonia), the original range (Mediterranean), and genetically distinct island populations from the Azores. We aim at assessing the degree of (1) phenotypic plasticity and (2) genetic adaptation underlying the variability in the above-mentioned fitness-relevant traits. We hypothesize that variability is either caused by (1) phenotypic plasticity alone, or (2) by the occurrence of admixture that happened to promote the northward range expansion. To assess the role of admixture in more detail, we will scrutinize populations along the supposed genetic cline in northern Germany. The width of the cline will reveal the intensity of selection between the admixed populations. The genetic setup of our focal populations will then be used to plan targeted behavioural experiments to understand the dispersal strategies and the relative competitive ability of spiderlings from the range expansion front.

Thesis topic: Environmental and genetic effects on fitness relevant traits in a range expanding spider.

B6 - Range expansion in lesser horseshoe bats

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

Thomas Näf, Sébastien Puechmaille & Gerald Kerth

State of the art: The European vertebrate fauna is highly dynamic due to both historical climatic variation and anthropogenic pressures. The ability of a species to track climatic changes by range shift is expected to be a major determinant of extinction risk (Science 313: 789). For some species, such as the Palearctic bat species Rhinolophus hipposideros, regressions and advances are quite well documented and represent unique opportunities to study how and why range limits move. Such dynamic range boundaries can be observed at the Northern edge of the current distribution of R. hipposideros, regions in which models of climate change predict a northward progression of this species during the next decades (Global Change Biol. 16: 561). Here we will investigate colonisation and colony formation via dispersal in the focal species, 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: Interconnected wild colonies at the Northern edge of the species’ range will be surveyed in Germany and combined with data already obtained from France (via associated partner E. Petit). Droppings will be collected from all colonies and genotyped using available microsatellite loci (protocol already optimised), allowing for individual identification and pedigree reconstruction. Non-invasive genotyping over consecutive years in the colony networks will be used to estimate demographic parameters (i.e. population size, population growth, vital [births, deaths] and dispersal [emigrations, immigrations] rates). Temperature and humidity will be monitored throughout the year within and outside the colonies, and habitat characteristics around the colonies will be mapped (Corine Land Cover). The project will focus on associations between realised dispersal and reproductive rate as well as on the influence of population density, social and environmental factors on dispersal and colony formation. Specifically, we will test the following hypotheses: (1) Dispersal (threshold trait) and dispersal distance are heritable traits; (2) individuals from newly formed colonies consistently exhibit higher dispersal rates and invest more into reproduction (due to less intense intraspecific competition in new colonies); (3) dispersal distance is influenced by habitat quality and availability. The obtained results will be used to parametrize a hybrid correlative/mechanistic model to predict range expansion in the species. This study will be carried out in collaboration with local conservation agencies and Dr. E. Petit, INRA (Rennes, France).

Thesis topic: Environmental and social factors influencing dispersal and colony formation in R. hipposideros.


Projects Cluster A | 2015-2018
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.

Projects Cluster B | 2015-2018
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.