Supervisor: PD Dr. Martin Haase, General and Systematic Zoology/Bird Observatory

Thesis topic: Historical and future range expansion of the New Zealand mud snail Potamopyrgus antipodarum.

Background: During phases of global change generalist species are predicted to have a higher survival chance than specialists. Climate change will produce winners and losers, the former surviving with a higher probability because they can adapt to novel situations and/or track their niche more successfully, i.e. have a higher potential for dispersal, than specialists. 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 including Europe, emphasising the species’ adaptive potential. The genetic diversity of the clonal European lineages is very restricted compared to the native range. Although clonal lineages accumulate mutations and evolve as well, albeit slower, phenotypic plasticity is probably more important for their successful range expansion than genetic adaptation.

Goals of project:We will reconstruct phylogeographies for both New Zealand as well as European populations based on genomic approaches to be developed using the genomic resources established in the previous generations of this project as well as by our external collaboration partner Maurine Neiman (Univ. Iowa). The phylogeographic analyses will allow to estimate modes as well as spatial and temporal dimensions of dispersal and serve, in conjunction with climatic data, as the basis for modelling future trends, in particular in Europe. The genomic data will also serve for the detection of genetic signatures of selection. As the colonization of Europe does not date back more than 200 years and the spread is fairly well documented, we expect to be able to assess the importance of genetic diversity and selection – and in turn phenotypic plasticity – especially for the conquest of the continent. As the remarkable variation of shell morphology, which is of adaptive significance, has an important genetic component, we will also assess the role of size and shape in the phylogeographic overall picture.

Required skills (The ideal candidate contributes a combination as comprehensive as possible of following skills to the project):

• Strong background in evolutionary biology and phylogenetics
• Experience with NGS techniques and analysis of big genetic data (scripting)
• Knowledge of statistics
• Modelling experience
• Willingness to travel long distances (New Zealand)
• Profound knowledge of English (spoken and written; basic knowledge of German is helpful)
• Driving license

Supervisors: Prof. Dr. Jan-Peter Hildebrandt and Dr. Christian Müller, Animal Physiology and Biochemistry

Thesis topic: Osmotolerance in the snail Theodoxus fluviatilis

Background: 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.

Goals of the project: We will further investigate the reasons why reaction norms of freshwater- and brackish water-ecotypes of Theodoxus fluviatilis cannot be made to match by stepwise acclimation of the animals to alien salinities. Our hypothesis is that this is due to genetic differences between the ecotypes. Based on the preliminary results of our genome sequencing project (PacBio) in cooperation with the Institute of Clinical Molecular Biology (IKMB) we will perform DNA re-sequencing with individuals from either ecotype and from within populations to compare these sequences and identify genetic differences related to local adaptations.

 Required skills: We are searching for candidates with scientific interests in comparative animal physiology (‘non-model organisms’).  The successful candidate has experience in bioinformatics (handling genomic data and doing sequence comparisons, e.g. for the identification of SNP patterns) and should be able and willing to perform molecular biological (cloning, PCR etc.) and biochemical (Western blotting, IHC, ISH) lab work.

Supervisors: Prof. Dr. Gerald Kerth & Dr. Alexander Scheuerlein, Applied Zoology and Conservation

Thesis topic: Responses within and between populations of four bat species to climate change scenarios and consequences for population persistence.

Background: Decreasing body sizes in response to global warming have been described in various taxa (‘global shrinking’; Nat Clim Change 1: 401). As body size and fecundity are often positively correlated, smaller body size may lead to a reduction in population growth rate and ultimately to lower population size and higher extinction risk. Interestingly, in a few species increasing body size in response to climate change has been observed, which may occur when warm weather is required for growth. The fitness implications of such poorly documented trends are unclear. Bats are long-lived, of high conservation concern and show behavioural responses that allow them to cope with weather variation, such as roost switching and social thermoregulation, as well as physiological responses such as torpor. Torpor, which is characterised by a reduction in metabolic rate and body temperature, 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 hamper growth of the juveniles. Evidence for possible cost-benefit trade-offs have also been found for behavioural responses to changing environmental conditions such as the timing of the departure from the hibernaculum in spring. Early departure increases mortality risk in some years, but may be beneficial in others, when food availability is high during warm weather conditions in late winter/early spring. In combination with their longevity and low annual reproductive output, possible limitations and costs of phenotypic plasticity, as well as underlying trade-offs, make bats a prime candidate to study the potential impact of climate change on individual fitness and population persistence. For more than 25 years, our group has been studying group-living and conservation-related questions in bats, using behavioural, ecological, molecular, physiological and demographic methods. This includes automatic monitoring of animals marked with RFID-tags as well as DNA genotyping and sequencing. As a result, long-term individualised field data and detailed genetic data are available for populations of four bat species living in different areas in Germany. So far, we could show that in female Myotis bechsteinii, long forearms were associated with lower survival in our study population in Franconia, for which we have a data set spanning 25 years. Moreover, we could show that rare catastrophic events during the hibernation period have a strong negative effect on population dynamics in different bat species. Our results suggest that long-lived hibernating bat species have the potential to plastically adjust to changing climatic conditions, but that this potential differs between species.

Goals of the projects: Building upon our previous findings, our next research goals are to assess to which degree the relative impact of genetic versus plastic responses differs among populations of the same species as well as between species and how this may effect population persistence. In the proposed project, we aim to test whether behavioural, demographic and morphological responses to varying weather conditions differ between syntopic bat species as well as among populations of the same bat species. Our ultimate goal is to understand to which degree the responses to environmental conditions vary within species (e.g., in replicated populations living in different regions of Germany) and to use these data in order to model the fate of the studied populations under different global change scenarios.

Required skills:

• Strong background in behavioural and evolutionary ecology
• Good knowledge of statistics, data handling and graphics in R or a similar language (e.g. MATLAB, Python, Julia)
• High motivation to develop population models and computer simulations, experience in numerical modelling is a plus
• Profound knowledge of English (speaking and writing)
• Organizational skills and ability to work in a team
• Experience with fieldwork (preferentially with bats) and knowledge of German will be an advantage but is not mandatory

Supervisors: Dr. Mia Bengtsson & Dr. Jörg Bernhard, Institute of Microbiology

Thesis topic: Establishing advanced techniques for metaproteome analysis to clarify the role of the L. pulmonarias microbiome.

Background: Lichens consist of a heterotrophic fungus (mycobiont) and an autotrophic photosynthetic partner (photobiont), generally green algae and/or cyanobacteria forming a symbiotic meta-organism. Additionally, lichen associated bacterial communities were identified as stable, specific, and structurally integrated partners of this symbiosis. Our culture-independent meta-omics approaches have created a comprehensive data collection (along geographical/climatic gradients) and have 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). We found, that the microbiota seems to contribute multiple aspects to the symbiotic system, including health, growth, and fitness(ISME J. 9:412, J Proteome Res. 16:2160, Microbiome 5:82). Some of the data indicate, that the strategy of functional diversification may support longevity of lichens and survival under harsh conditions. The highly versatile microbial community may enable the lichen holobiont to adapt to environmental changes (such as global warming). Our project complements RESPONSE by investigating phylogenetic and functional changes of the lichen symbiotic community affected by different climate conditions. 

Goals of the projects: This project will apply new data analysis techniques to reveal molecular mechanisms of the model lichen L. pulmonaria during adaptation to environmental changes along climatic temperature and moisture gradients. Preliminary analyses, comparing samples of L. pulmonaria from a variety of European sites suggest the presence of a partly stable microbiome, however, also indicated significant differences between the proteomes of several lichen microbiomes in contrast to the rather stable fungaland algal protein profiles (see also J Proteome Res. 16:2160). We hypothesize, that especially changes in the composition and functionality of the microbiome enable the lichen holobiont to cope with environmental changes. We will extend our current knowledge: by (1) a deeper analysis of the already collected data from the geographic/climatic gradients, (2) applying more advanced data processing techniques such as multiple missing value imputations and multiple and corrected statistic testing to perform reliable statistical analysis (Masterthesis Jasmin Franke, 2020), (3) evaluating the generated hypothesis by specifically designed transplantation experiments in close collaboration with the Karl-Franzens-University Graz and (4) supporting the application of computer models predicting the properties of the sampling site from the found constituents of the microbiome.

 Required skills:

• Background in microbiology, molecular biology or biochemistry
• Experienced in wet lab work
• Strong expertise in statistics and data analysis
• Expertise in R, data integration and visualization
• Fluent English (speaking and writing)
• Very good organizational skills and strong ability to work cooperatively in a team

Supervisors: Prof. Dr. Martin Schnittler & Dr. Manuela Bog, General Botany & Plant Systematics

Thesis topic: The role of microenvironment on plant performance: Influence of habitat adapted symbioses at the treeline in White Spruce.

Background: White spruce (Picea glauca) is the main northern and elevational treeline species in Alaska, forming often monospecific stands. A previous study shows that the genetic differentiation of populations as measured with neutral markers is low, which hints towards effective long-distance gene flow mediated by pollen. Further, it was found that most of the variance in growth performance of individual trees could not be explained by genetic constitution or mesoclimatic differences between plots, thus yet unknown microenvironmental factors appear to be crucial (Zacharias et al., in prep.). Symbiotic interactions represent one part of the microenvironment and it was documented that members of the Pinaceae family will not grow into adult trees without their co-dispersed ectomycorrhizal fungi (Plant Soil 454:3) which gives them a decisive role in the development of the trees. It was further shown that symbioses can lead to an advantage at the seedling stage of long-lived trees (J Ecol 108:908) and increase the fitness to abiotic stress which may play a big role in how plants react to climate change (PLoS ONE 6: e14823). 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). In trees, selection is mainly effective during establishment (Theor. Popul. Biol. 42: 172) and site conditions are crucial for recruitment success. In cooperation with the working group Prof. Wilmking (B2) which records growth performance and will try to trace back abiotic microenvironmental factors, we will focus on symbiotic interactions of white spruce.

Goals of the projects: Subject to the global health situation, individual trees in the established plots in Alaska will be examined for their symbiosis partners by DNA metabarcoding to assess the influence of microbial interaction partners on tree performance and to identify possible benefits of such interactions at extreme locations (treeline) compared to reference locations (forest stands). Already established SSR markers will be used to assign sampled fine roots to already known genotypes for the trees (Canad. J. Forest Res. 48:1577). Further comparative cultivation studies with inoculated and non-inoculated tree seedlings under controlled conditions are planned to test if the choice of mycorrhizal partners reflects local genetic adaptation or will be determined by the micro-environment. The project is carried out in close cooperation with project B2 (Prof. Wilmking). Within the frame of a structured PhD school, field work in exciting landscapes, with 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.

Required skills:

• Strong background in fungal mycorrhiza and/or plant ecology
• Preferably a background with bioinformatics pipelines for next generation sequencing methods (Illumina, fungal metabarcoding with ITS1/2 markers)
• Knowledge of statistics, data handling and graphics (background in R or Phyton helps)
• Excellent knowledge of English (speaking and writing)
• Feeling at home in both field (working under difficult conditions in boreal and arctic ecosystems) and lab (molecular genetic methods, sterile and non-sterile cultivation techniques, bioinformatics)
• good organizational skills and strong ability to work cooperatively in a larger team

Supervisors: Prof. Dr. Jürgen Kreyling & Dr. Barbara Bauer, Experimental Plant Ecology

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

Background: 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 for species persistence, however, are unclear. A better understanding of these factors and their incorporation into projections of species persistence and potential future range shifts are crucial to provide guidance for long-term sustainable forest management.

Goals of the projects: We will quantify the importance of phenotypic plasticity and genetic adaptation of F. sylvatica for projections of species persistence and range shifts. Existing data of phenotypic plasticity, heritability, and genetic adaptation will be used to constrain hybrid species distribution models (e.g. Ecol. Lett. 19: 1468) and to develop species distribution models taking within-species variability into account (e.g. Ecol. Evol 3: 437-449). This project focuses on modelling and profits from existing data. Additional field sampling in existing, long-term provenance trials is possible, but not mandatory.

Required skills:

• University degree (M. Sc. or equivalent) in biology, ecology, environmental physics, biomathematics or a related subject
• Strong background in statistical and/or simulation modeling and data handling in R or a similar scripting language (e.g. MATLAB, Python)
• Knowledge in plant ecology and/or forestry
• Experience with or strong interest to learn about species distribution modelling and eco-evolutionary dynamics
• GIS and spatial data handling skills are a plus
• Organizational skills and ability to work in a team
• Profound knowledge of English (speaking and writing)

Supervisors: Prof. Dr. Martin Schnittler & Dr. Nikki Dagamac, General Botany & Plant Systematics

Thesis topic: Local genetic adaptation through evolution of reproductive systems in myxomycetes

Background: Amoebae of nivicolous myxomycetes (slime molds, Amoebazoa) are common in alpine (Sci. Rep. 8: 11662) and many lowland (Fungal Ecol. 39: 80) soils, playing a crucial role in soil ecosystems (PLoS ONE e2527) as predators of bacteria. Dispersal occurs via airborne spores produced in fruiting bodies; gene flow between mountain ranges seems to be high but not unlimited (Protist 167: 234). This may lead to outbreeding depression, but many species seem to segregate by a yet unknown mechanism into reproductively isolated units (putative biospecies), which should allow for local genetic adaptation. This is the case for our model species Physarum albescens, with more than a dozen of such units, recognizable by their barcodes (Shchepin et al., in prep.) and occurring in most mountain ranges of the northern hemisphere (Dagamac et al. 2020, Fungal Ecol., in review). In addition, asexual propagation via spores may occur (Janik et al. 2020, Protist, in press). A hint on the underlying mechanisms give macrospores showing roughly the double volume of normal spores (Woyzichovski et al. 2020, submitted).

Goals of the projects: We first want to focus on the distribution of putative biospecies, using a combination of fruitbody sampling (barcoding plus genotyping by sequencing, GBS) and metabarcoding (to detect possible non-fruiting units that are out of their optimum range) to (i) assess their distribution and (ii) model ecological niches with mesoclimatic data. In addition, spore size will be quantitatively assessed via particle measurement (flow cytometry) as a proxy for dispersal potential. Subject to the global health situation, we want to extend the sampling on the entire northern hemisphere to relate gene flow between mountain ranges to differences in spore size. As a second line of evidence, we want to use GBS to test for asexual reproduction via spores (clones that cover distances that cannot be bridged by active/passive amoebal migration) to test the hypothesis that asexual reproduction is a favourable strategy to colonize marginal habitats. This could lead to a new response model for very dispersive organisms on changing environments: on one hand, long distance dispersal allows to run out changing environments, on the other hand, segregation into reproductively isolated units with limited occurrence allows local genetic adaptation.

Required skills:

• Some background in evolutionary biology of lower organisms, best in protistology
• Preferably first experience with bioinformatics pipelines for next generation sequencing methods (Illumina, metabarcoding and/or GBS)
• Knowledge of statistics, data handling and graphics (desirable is Phyton or R)
• Excellent knowledge of English (speaking and writing)
• Willingness to combine field work (sampling in different mountain ranges) with lab work (molecular genetic methods, bioinformatics)
• good organizational skills and strong ability to work cooperatively in a larger team
• if you have never seen a myxomycete: do not be afraid, we will fix that!

Supervisors: Prof. Martin Wilmking & Dr. Tobias Scharnweber, Landscape Ecology and Ecosystem Dynamics

Thesis topic: Treeline dynamics of Picea glauca in Alaska – From plot scale mechanisms to species distribution models

Background: 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 (Glob Change 23: 5509), 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 (Ecology Letters, 14, 373). But how well are local populations adapted to expected climatic extremes and gradual shifts in climate? Here we will combine field and modelling studies to 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.

Goals of the projects: This project will take advantage of a large existing field and genetic data set of white spruce from several study sites across Alaska (over 1000 trees) and the species distribution range (over 10000 trees). Additional field work will target specific data needs, and the student will develop and “fine-tune” his/her project with the help of the supervisor after acceptance. Ideally, the student will use field-based data on growth performance, seedling success and phenotypic plasticity of white spruce to inform local and regional species distribution models. You will become part of a dynamic, international working group, and your project can develop close cooperation with project A5 (supervised by Prof. Schnittler). And, last but not least, awesome landscapes and exciting field work is waiting for you, as is the small but vibrant Baltic sea coast town of Greifswald.

Required skills:

• Strong background in plant ecology, forestry or ecosystem ecology
• Knowledge of statistics, data handling and graphics (preferably in R)
• Excellent knowledge of English (speaking and writing)
• Expertise in ecological field work and field methods (preferentially with woody species)
• Willingness to work under strenuous conditions for extended periods of time in harsh environments
• Very good organizational skills and strong ability to work cooperatively in a team
• Prior modelling experience is a plus

Supervisors: Prof. Dr. Steffen Harzsch & Dr. Jakob Krieger, Cytology and Evolutionary Biology; Dr. G. Torres & Dr. L. Giménez, Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

Thesis topic: Global ocean change drives range expansion of marine species: exploring northern distribution limits

Background: Coastal and shelf seas are characterized by a high biodiversity and unique ecosystems and are fundamentally important for sustaining and enhancing human welfare and industry. It is forecasted that in the next 50 – 100 years, between 50 and 70 % of the population will be living in coastal areas which creates competing demands from different sectors such as tourism, fisheries and aquaculture, on scarce coastal and shelf sea resources. Furthermore, anthropogenic stressors related to climate change already have a major impact on coastal ecosystems by affecting environmental drivers such as water temperature, salinity, pH and oxygen content. Crab species are key organisms in many marine habitats and are renowned for their massive impact in coastal ecosystems where they act as strong predators but also serve as an important link in the food web because of their complex life cycle. In many crustaceans, dispersing pelagic larvae are essential for population persistence and dispersal, and larval stages of crabs are known to be more vulnerable to fluctuations in environmental key parameters in the water column than the adult animals. Therefore, one area of research on population persistence and range expansion in crustaceans addresses the capacity of crustacean larvae to tolerate the combined effects of environmental drivers. Within the framework of RESPONSE, we have previously quantified the combined effects of abiotic stress on various aspects of larval quality in the European shore crab Carcinus maenas, an iconic member of intertidal ecosystems of many European coasts. These experimental studies were carried out at the Alfred-Wegener-Institute (AWI) at the island of Helgoland using animals from the local population of Carcinus maenas. Because multi-population comparisons are instrumental to species responses to climate change, we are also analysing if larvae of this species taken from mothers from different populations across most of its native range (from S. Spain to S. Norway) display different levels of resistance to environmental stress (temperature and salinity).

Goals of the project: Our previous studies have suggested, C. maenas has a strong potential to expand its native range northwards along the Norwegian coast, as a consequence of global warming. The project advertised here seeks to predict the future northern range expansion of this species and will be carried out in collaboration with Dr. Gabriela Torres (AWI Helgoland) and Dr. Luis Giménez (AWI Helgoland and School of Ocean Sciences, Bangor University, Wales). In a common garden experiment, larvae from Norwegian crab populations will be reared under a previously tested regime of thermal stress at the AWI Helgoland. To that end, we will compare the performance of larvae from edge populations at the northern distribution limit with those from the core of the Norwegian distribution range. Building on the expertise from the previous project, we will measure key parameters of larval performance such as survival, developmental duration, respiration and feeding rates, biomass, and gene expression of target genes. In a second step, we will establish predictions for the northern range expansion of this species using phenological models.  

Requirements: Candidates should have a strong background in aquatic biology (e.g. ecology or physiology), must be prepared to work independently for extended time periods at a marine biological station and should have experience in culturing marine organisms. The candidate should also be prepared to carry out field sampling over extended time periods and spatial scales (including having a driving licence). It is desired that candidates have good knowledge of statistical methods and some basic knowledge of programming in R or a similar software (e.g. Matlab, Python). These skills will facilitate the development of modelling approaches for species persistence predictions. Organizational skills and ability to work in a team are also essential as well as a profound knowledge of the English language (speaking and writing) as well as basic knowledge in German.

Supervisors: PD Dr. Peter Michalik, Prof. Dr. Klaus Fischer, NN, Zoological Institute & Museum, Animal Ecology

Thesis topics: Drivers of rapid range expansion in an European butterfly: beyond climate and dispersal potential

Background: For investigating responses to anthropogenic climate change and specifically range dynamics, butterflies seem to comprise an eminently suitable taxon (Parmesan et al. 1999). This is because poleward range shifts, as a possible response to climate change, have been repeatedly documented, owing to particularly solid data bases in terms of species records and a high sensitivity to thermal conditions (Konvicka et al. 2003; Settele et al. 2008). Additionally, important ecological, evolutionary, and behavioural traits are particularly well understood in butterflies, including knowledge on the temperature-dependence of phenology as well as physiological and behavioural adaptations to climatic conditions (Dennis 1993; Klockmann et al. 2016). Results obtained from this model taxon will also be relevant to other climate-sensitive organisms with similar population structures such as grasshoppers, beetles, rodents, and frogs (Parmesan et al. 1999).

This study explores the factors driving rapid range expansions, exploiting the spectacular case of the southern small white Pieris mannii. This butterfly was confined to the Mediterranean and was first found north of the Alps in 2008. Since then it gradually extended its range and is now even sighted in northern Germany. Recent work on this species indicated that the recent range expansion is unlikely to be directly caused by anthropogenic climate change. Rather, expanding as compared with historical populations show a more generalist lifestyle, namely a reduced host-plant specialization, and an overall increased fecundity. Currently, it is unclear whether these genetic changes occurred before the range expansion or during the course of it.

Goals of the project: We will here use population geneticanalyses to determine (1) the geographic origin of newly established edge populations, (2) the degree of genetic differentiation between edge and source populations, and (3) the potential role of genetic modifications (e.g. admixture) as a potential driver of range shifts, and (4) landscape features affecting gene flow and thus dispersal. We will apply double digest restriction-site associated DNA sequencing (ddRADseq) to call SNPs using a de novo pipeline. Using the resulting SNP panel we will (1) explore the population genetic structure (STRUCTURE), (2) investigate the impact of landscape features on population structure (distance-based redundancy analyses, dbRDA), (3) model spatial patterns of genetic diversity and gene flow (estimated effective migration surface; EEMS), (4) analyse isolation by distance, resistance and environment based on distance and resistance surfaces derived from MAXENT distribution modelling, and (5) search for outlier loci under selection (BAYPASS, FDIST2). The combination of using (i) a species with a particularly well-documented and outstandingly rapid range expansion and (ii) modern population and landscape genetic methods is expected to generate novel insights into the factors underlying a species’ ability to establish in new habitats.

We will test the following hypotheses:

1. We hypothesize that the populations established in Germany originate from southern France (subspecies alpigena). We further predict an admixture event between alpigena and the Italian subspecies rossii, which has promoted the emergence of more dispersive phenotypes and an enhanced ability to settle within the new range.
2. We expect intraspecific genetic differentiation between edge and core populations to be high, due to short-distance dispersal in combination with allele surfing. Thus, the frequency of specific alleles will be high at the leading edge, while overall genetic diversity will be low.
3. Landscape features, namely mountain regions, which strongly impact dispersal routes.
4. Newly established edge populations show local adaptation as indicated by outlier loci under selection.

Finally, we may compare our findings with those obtained from the Green-veined white Pieris napi, which is a species with a circumboreal distribution and has not shown any recent range expansions. A much less pronounced population genetic structure and a weaker impact of geographic features is expected here.

Required skills:

• Strong background in behavioural and evolutionary ecology
• Interest, knowledge and previous experience with biochemical and genetic analyses
• Knowledge in experimental design, data handling and statistical analyses
• Interest in entomology and lepidopterology
• Expertise in field methods (preferentially with insects and butterflies)
• Interest in flight biomechanics
• Good command of English; basic knowledge in German would be an advantage
• Organizational skills, willingness and ability to work in a team

Supervisor: Prof. Gabriele Uhl, General & Systematic Zoology

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

Background: 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, which moved from the Mediterranean region into continental climates as far as Scandinavia and Finland in less than 100 years. Consequently, its current distribution spans 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). To understand the range expansion dynamics, and subsequent adaptation of these spiders in novel environments, we use common garden experiments to compare populations of A. bruennichi from the range expanding front of the distribution (Baltic countries) with those of the original range in the Mediterranean.

We have developed state-of-the-art genomic resources for the species (bioRxiv: doi.org/10.1101/2020.05.21.103564), as well as detailed population genomic data, which we use to detect adaptation at the sequence level. Common garden physiological experiments at the phenotypic level point to both genetic adaptation and plasticity as important factors contributing to cold tolerance and overwintering success. Gene expression studies and metabolomic data will provide the connecting link between genomic and phenotypic evidence for adaptation. Our work contributes to the overall aim of the RTG by pinpointing the mechanisms driving success in species that colonise, and subsequently adapt to, new habitats.

Goals of the project: We will investigate variation between populations from the northern range limit (Estonia) and the core of the range (Southern France). In this project, we aim to assess the degree of phenotypic plasticity and genetic adaptation underlying the variability in traits related to temperature tolerance, specifically in adaptation to colder winters. The methodology will include field collection of spiders, with overwintering of offspring in a common garden design followed by physiological measurements, including gene and metabolite expression. We will work closely with Henrik Krehenwinkel (Uni Trier) and an interdisciplinary collaboration network at our university to generate and analyse the expression data. Analysis will be aided by the use of our high quality genome assembly. We will use these fitness-relevant data to parameterize various models with the aim of predicting population persistence and distribution of A. bruennichi in the future.

Required skills:

• Strong background in evolutionary biology and molecular biology
• Interest in environmental physiology
• Knowledge of statistics (preferably in R)
• Interest in species distribution modelling
• Excellent knowledge of English (speaking and writing)
• Very good organizational skills
• Strong ability to work cooperatively in a team

Supervisors: Prof. Dr. Gerald Kerth & Dr. Jaap van Schaik, Zoological Institute & Museum

Thesis topic: Combining population genetic data and modelling to explore the influence of environmental and social factors on range expansion and colony formation in R. hipposideros.

Background: 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, as the Palearctic bat R. hipposideros, range 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 climate change models predict a northward progression of this species during the next decades (Glob Change Biol 16: 561). However, these predictions do not take into account the species’ dispersal capacity and trade-offs between life history traits and sociality that evolve in expanding populations (Ecol Lett 13: 1210). For example, (obligate) coloniality may fundamentally constrain the effect of individual dispersal decisions. To date, how dispersal leads to novel colony formation, and thereby range expansion at the edge of a species’ distribution, remains unknown for bats. The differing ways in which dispersal can lead to the foundation of new colonies and range expansion will be reflected in the genetic structure and diversity of the newly established population. As genetic diversity represents the raw material upon which selection can act, allowing species to respond to changing environments, it is crucial to better understand factors shaping genetic diversity in leading-edge populations. During the first two project phases of RESPONSE, our international team obtained over 17,000 multilocus genotypes from 20 colonies (2015-2020) of an expanding meta-population of R. hipposideros located in Thuringia. Life history traits were estimated from an integrated population model that was developed to make full use of the information contained in non-invasively collected multilocus genotypes. By using population size estimates, sex ratios and genetic diversity data in a combined model we estimated survival, fecundity and dispersal in our target colonies. Results indicated a higher rate of dispersal (ca. 2-5 %) in German populations than in those of a stable population in France (movement between colonies; < 0.1 %), fitting our expectations of higher dispersal rate in the expanding population. In the second phase, individual genotyping is being supplemented with higher resolution SNP data to yield individual identity, in order to track dispersal events and gain a better understanding of the genetic composition of newly established colonies.

Goals of the projects: Building upon the findings described above, 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), most notably in newly establishing colonies. These parameters will be used to parametrize models to predict colony formation and range expansion in R. hipposideros and compare it to other bat species for which similar data are available. Modelling will be done in cooperation with our local partner Barbara Bauer (Projekt P).

Required skills:

• The candidate should have (or be willing to develop) skills in population dynamics, population genetics and/or species distribution modeling
• Excellent written and spoken English,
• Good knowledge of statistics, data handling and programming in R or a similar language (e.g. MATLAB, Python, Julia, C++)
• Good organizational skills and ability to work in a team (incl. with NGOs),
• Experience with fieldwork (preferentially with bats) and knowledge of German will be an advantage but is not mandatory