Every semester, EES organise a seminar series, which takes place on Mondays at 17:00 at Biozentrum, Großhaderner Str. 2, 82152 Planegg-Martinsried, Lecture Hall B 01.027
Speakers are invited from mainly around Europe across all three areas (Evolution, Ecology and Systematics), leading to a wide-range of presented research topics.
Winter Semester 2017/2018
Stefan Lüpold - "Sperm wars: rise of the giants"
University of Zurich, Switzerland
Abstract: Sexual selection drives the evolution of male ornaments and armaments used in gaining access to mates. However, whenever females mate with multiple males, sperm of different males will compete for fertilization. Selection for sperm that are both more competitive and better able to overcome the challenges of the female reproductive tract has brought about tremendous variation in sperm size and shape. I will discuss our recent work on the causes and consequences of variation in sperm form and function, including the evolution of the longest sperm ever measured. I will further discuss how males trade off the allocation of their limited resources between producing masses of high-quality sperm and the costly ornaments and armaments to gain mating opportunities in the first place.
Christiane Fuchs - "Estimating single-cell heterogeneities from small cell populations"
HelmholtzZentrum München, Germany
Abstract: Cell-to-cell variation in gene expression occurs in a number of biological contexts, such as development and cancer. Discovering such heterogeneities from large bulks of cells is impossible due to the inherent population averaging. The analysis of single cells, on the other hand, is challenging because of e.g. technical noise. Here, I show that we can infer single-cell regulatory states by statistically deconvolving measurements from small groups of cells. This averaging-and-deconvolution approach allows us to quantify single-cell heterogeneities while avoiding the measurement noise of global single-cell techniques. Application of the statistical technique to breast epithelial tissues helped gain new insights about some breast cancer associated genes. I will outline how the method can be used to detect transcriptomic heterogeneity in leukemia cells within the CRC 1243 “Cancer Evolution”.
Robert Page - "Beyond the Superorganism: how social mechanisms evolve"
Arizona State University, USA
Abstract: More than a century ago (1911) William Morton Wheeler proposed that social insects should be considered organisms because they have the defining properties of individuals "... a complete, definitely coordinated and therefore individualized system of activities, which are primarily directed to obtaining and assimilating substances from an environment, to producing other similar systems, known as offspring, and to protecting the system itself and usually also its offspring from disturbances emanating from the environment. The three fundamental activities enumerated in this definition, namely nutrition, reproduction, and protection ... ." In 1928 Wheeler first used the term "superorganism" to describe social insects, which became a permanent part of the vocabulary of social insect biologists. But, Wheeler's superorganism was little more than a metaphor created to explain the evolution of cooperative behavior, something he thought impossible with Darwinian selection, focused on the struggle for life and reproduction, best depicted by the phrase of Herbert Spencer "the survival of the fittest". Over the past century the metaphor has gone through phases of use and abuse and at least two different "revivals", but always as a metaphor, a conceptual scaffold on which analogies are hung, offering a way to explain observed social phenomena, but little in the way of predictive hypothesis and new questions. What is missing, in my view, is a theory of the superorganism that incorporates and integrates the following components: 1) how cooperation resulting in reduced reproduction (altruism) evolves (a major theoretical enterprise for 50 years), 2) how colony level selection affects multiple levels of biological organization -- genes to societies, 3) the mechanisms by which coordinated division of labor emerges from a group of individuals without a global control system and how such mechanisms evolve. I will discuss a 25-year experiment with honey bees where I addressed components 2 and 3.
Daniel Jeffares - Populations, genomics and transposon mutagenesis in the (fission) yeast model
University of York, UK
Abstract: The fission yeast Schizosaccharomyces pombe is an important model for molecular and cellular biology. In contrast to the budding yeast, we knew very little about the diversity, ecology or evolution of the species until very recently. I’ll introduce what little is known about the ecology of this yeast (1), and then describe three of my studies of genome diversity and function. First, I’ll outline our study of genomic and phenotypic diversity, where we describe population structure, date the dispersal of the species and show that genome-wide association studies are feasible in this species (2). Secondly, I’ll describe our analysis of structural variation from short read data demonstrating that copy number variants both contribute to heritable traits, and are unstable (3). On a slightly different track, I’ll describe our recent analysis of saturating transposon mutagenesis in S. pombe (unpublished). In this study, we generated very dense transposon insertion libraries using the Hermes transposon, to one insertion per 14nt of the genome. We developed a hidden Markov Model that uses the transposon insertion density to classify the relative importance of each position in the genome. We show that HMM states assign similar functional constraints to comparative genomics and genetic diversity, but with far higher resolution. This data will bring us closer to quantifying the functional significance of every base in the genome.
Jonathan Jeschke -
Freie Universität Berlin, Germany
Daniel Hooper -
Cornell University, USA
Christian Schlötterer -
VedMedUni Vienna, Austria
Katie Peichel -
University of Bern, Switzerland
Samantha Patrick -
University of Liverpool, UK
Summer Semester 2017
Kris Murray - "Pathogeography - the biogeography of human infectious diseases"
Imperial College London, UK
Abstract: With infectious diseases having repeatedly altered the course of human history, and still responsible for almost a fifth of the global burden of disease, understanding the distributions of infectious diseases is a central public and global health objective. I will discuss some recent work in which we show that human infectious diseases exhibit striking biogeographic grouping patterns at a global scale, reminiscent of “Wallacean” zoogeographic patterns. This result is surprising, given the global distribution and unprecedented connectivity of humans as hosts and the homogenizing forces of globalization; despite these factors, infectious disease assemblages appear to remain fundamentally constrained in their distributions by ecological barriers to their dispersal or establishment. Biogeographic processes thus appear to provide an overarching context in which other factors promoting infectious disease emergence and spread are set, providing a potentially useful prior with which to evaluate a range of disease risks and potential management interventions.
Robert Whittaker - "Oceanic island biogeography through the lens of the General Dynamic Model"
University of Oxford, UK
Abstract: The general dynamic model of oceanic island biogeography (GDM) provides a theoretical framework incorporating the dynamics of island platforms alongside the key biological drivers of immigration, extinction and speciation. It provides an essentially non-equilibrium framework generating novel predictions for emergent diversity properties of oceanic islands and archipelagos. Based on efforts of the biodynamics of islands workshop group I review progress, both in testing the GDM’s predictions and in developing and enhancing ecological-evolutionary understanding of oceanic island systems, through the lens of the GDM. The presentation considers such themes as: 1, what we have learnt from species-area relationships for remote islands; 2, macroecological tests of the GDM using a space-for-time rationale; 2, extensions of theory to islands following different patterns of ontogeny; 3, the implications of GDM dynamics for lineage diversification and trait evolution; 4, the potential for downscaling GDM dynamics to local-scale ecological patterns and processes within islands; 5, island theory and non-native species.
Justin Crocker - "Decoding evolution and development: from enhancer structure to function"
EMBL Heidelberg, Germany
Abstract: In animals, Hox transcription factors define regional identity in distinct anatomical domains. How Hox genes encode this specificity is a paradox because different Hox proteins bind with high affinity in vitro to similar DNA sequences. Here, I will show that the Hox protein Ultrabithorax (Ubx) binds specifically to clusters of very low-affinity sites in Drosophila. These low-affinity sites conferred specificity for Ubx binding in vivo, but multiple clustered sites were required for robust expression when embryos developed in variable environments. Although most individual Ubx binding sites are not evolutionarily conserved, the overall enhancer architecture—clusters of low-affinity binding sites—is maintained and required for enhancer function. Natural selection, therefore, works at the level of the enhancer, requiring a particular density of low-affinity Ubx sites to confer both specific and robust expression. Finally, I will discuss results that suggest that low-affinity sites drive efficient transcription by utilizing nuclear microenvironments with high concentrations of transcription factors and cofactors. Mechanisms that generate these microenvironments are likely to be a general feature of eukaryotic transcriptional regulation.
Martin Wikelski - "The ICARUS Project"
Max Planck Institute for Ornithology, Konstanz, Germany
Abstract: The goal of the ICARUS (International Cooperation for Animal Research Using Space) Initiative is to observe global migratory movements of small animals through a satellite system. Global data about animal movements are indispensable in our today international networked world to understand how to safe human health and wildlife simultaneously. To this date scientists are unable to follow small animals and insects on their long journey. Billions of songbirds move every year from continent to continent. Also many bats and numberless species of insects manage long distances and in doing so possibly move from one continent to another. We do not know exactly. However, this knowledge plays a fundamental role to understand the propagation of pathogens through their hosts for instance to preserve ecosystem services or to predict natural disasters through intelligent sensors of animals. To remedy the worldwide lack of knowledge about the distribution and the individual migratory habits of small animals and insects, an international consortium of scientists got the ICARUS project underway in 2002. With the data generated by ICARUS, scientists expect revolutionary new insights about life, behavior, vital functions and death of the animals on our planet. The globally collected data allows us among other things conclusions for the spread of diseases (zoonosis), understanding of climate change and disaster forecast. The research results to be expected here are of invaluable importance for mankind and finally for life on earth.
Susanne Foitzik - “The evolution of division of labor and parasite defense: from the phenotype to changes in gene expression and regulation”
University of Mainz, Germany
Abstract: Social insects show fascinating behaviours, from slavery, over social immunity to an effective division of labour in their societies. In this talk, I will give insights into the evolution and molecular basis of behaviour in ants and present recent results that reveal, which proteins, genes and gene regulatory mechanisms are involved. In most insect societies, division of labour among workers is age dependant and we demonstrate this also for the small Temnothorax ants. Transcriptome analyses allowed us to identify candidate genes, which control the behavioural transition from brood care to foraging behaviour. RNAi-mediated knockdown of a brood care gene, vitellogenin-6, showed that division of labour is indeed controlled via response thresholds to social cues, which shift with gene expression. Inhibition of histone-acetyltransferase revealed that behavioral transitions in ant workers are controlled by histone acetylation via an alteration of gene expression. Parasites can also affect ant behaviour, either by direct manipulation or by selecting for behavioral defense mechanisms. Our study on a cestode parasite and its ant host show, that parasite infection not only affects behaviour (by lowering general activity), but also increases longevity. Proteome analyses of proteins released by the cestode into the host indicate that the parasite directly manipulates the host phenotype. Finally we investigate the evolution of slavery in ants and can show, which genes are differently expressed during slave raids and host defence in three slavemakers and their three hosts. We could functionally characterize some of these candidates using RNAi. Selection analyses reveal that different genes are under selection in independent origins of slavery, suggesting convergent evolution of these fascinating behaviours.
Meike Wittmann - "Fluctuating balancing selection and its effects on neutral genetic diversity”
University of Vienna, Austria
Abstract: For organisms with several generations per year, seasonally fluctuating selection can be a powerful mechanism to maintain genetic polymorphism. For example, an allele favored during summer may stably coexist with an allele favored during winter, a form of balancing selection. Despite intense debate over decades, it is still unclear how much of the variation observed in the genomes of natural populations is due to balancing selection. In recent years, evolutionary biologists have started scanning genomes for genetic footprints of balancing selection (e.g. regions of increased diversity and positive Tajima's D). However, these scans have generally assumed the simplest form of balancing selection where alleles are maintained at constant frequencies over time. There is currently insufficient theory to tell us what genetic footprint to expect under seasonally fluctuating selection, and how to distinguish it from neutrality but also from other forms of balancing selection. In this talk I will present results from coalescent models and stochastic simulations to characterize the impact of fluctuating balancing selection on neutral genetic diversity at various scales: at closely linked sites, at the scale of the chromosome, and at the genomic scale.
Winter Semester 2016/2017
Nico Posnien - "Systems-Evo-Devo: Evolution of developmental gene regulatory networks”
University of Göttingen, Germany
Abstract: The size and shape of an organism and its organs is tightly controlled during embryonic and postembryonic development to ensure proper functionality. However, in the light of the breath-taking diversity of body forms observed in nature, adult features are certainly targets for evolutionary changes. This contradiction suggests that developmental gene regulatory networks (GRNs) are constrained to a certain level, but nodes within this network are prone to change to give rise to morphological divergence.
We have previously shown that the three closely related Drosophila species D. melanogaster, D. simulans and D. mauritiana exhibit natural variation in eye size and overall head morphology. In this survey, D. melanogaster has the smallest eyes and D. mauritiana has the largest eyes. The aim of our research is to identify flexible nodes within the GRN underlying adult head formation in these three Drosophila species. To this end, we combine unbiased genome-wide approaches like quantitative trait loci (QTL) mapping and comparative transcriptomics with developmental genetics and geometric morphometrics to identify genes and developmental processes responsible for the observed differences in head morphology.
Our genome-wide expression analysis of different developmental stages of eye and head development shows that many genes that are differentially expressed between D. melanogaster and D. mauritiana are regulated by the GATA transcription factor Pannier (Pnr). Using interspecific crosses with D. melanogaster pnr deficiency lines, we provide further support for an involvement of the pnr locus. Eventually, we place pnr in the developmental gene regulatory network underlying eye development. All this data strongly suggests that divergence at the pnr locus is likely to be responsible for the morphological differences between D. melanogaster and D. mauritiana.
Qi Zhou - "Evolution of sex chromosomes of flies, birds, snakes and beyond"
University of Vienna, Austria
Abstract: Sex is a nearly universal biological feature, and is determined by sex chromosomes in many, but not all the eukaryotes. After the birth of sex-determining genes, X and Y chromosomes start their separate evolutionary trajectories and form opposite patterns of gene content and epigenomic landscapes. Over the past several years, I have studied birds, snakes and Drosophila species, and will use them as examples to introduce my current and future research. We have studied complete genomes of 50 bird species. We reconstructed complex scenarios of recombination loss between sex chromosomes, caused by Z- or W-chromosome inversions, and uncovered a great diversity of their evolution rate comparing to the mammalian XY systems. In Drosophila, we show Y chromosomes can degenerate very quickly, manifested by increased bindings of heterochromatin modification, and decreased bindings of euchromatin modification together. This process is not random across the Y-linked regions, but constrained by the ancestral chromatin configuration. It is probably triggered by the vulnerability of Y against the transposable element insertions, and further results in the chromosome-wide silencing of Y-linked genes. It also creates an arms-race between the piRNA and TEs, which forms my main topic of research in Vienna for the next five years.
Tom Tregenza - "Ageing in the wild"
University of Exeter, Cornwall, UK
Abstract: In recent years a growing number of field studies have identified senescent declines (age-related degeneration) across a broad range of taxa. However, studies examining changes in behaviour are rare, and insects in their natural context have hardly been studied all, despite their importance as laboratory model systems. I will describe our decade long study of a population of wild crickets which has allowed us to analyse patterns of mortality and the effect of age on a suite of traits including naturally and sexually selected behavioural traits measured at the individual level. We find substantial evidence of actuarial senescence, with the probability of death increasing with individual age. However the nature of these declines varies among years and the key prediction that males should age faster than females is only true in some years. Behavioural traits show a range of patterns, although evidence of senescence is abundant. I will discuss potential explanations for the striking variation we observe.
Patrik Fink - "The challenged consumer - aquatic herbivores’ response to variable resource quantity and quality”
University of Cologne, Zoological Institute, Workgroup Aquatic Chemical Ecology &
Heinrich-Heine-University of Duesseldorf, Institute for Zoology and Cell Biology, Germany
Abstract: Herbivores play a key role in aquatic food webs as they are responsible for the trophic transfer of photosynthetically assimilated carbon into the animal food web, which makes them crucial for the functioning of marine and freshwater ecosystems. It is hence of paramount importance for ecologists to understand the reasons for constrained efficiency of the transfer of matter and energy at the plant-herbivore interface, but also the potential compensation mechanisms that consumers have evolved to cope with such constraints. This relies on a firm understanding of food web structure and the physiological ecology of the respective organisms. In this presentation, I summarize some of my recent research on the structure of aquatic food webs with particular focus on aspects of biodiversity and the impact of invasive species. I highlight some of the nutritional constraints for the efficient transfer of algal biomass to benthic and pelagic herbivores and their consequences for herbivore fitness. I further discuss potential strategies of aquatic herbivores to compensate or overcome nutritional constraints through the evolution of physiological and/or behavioural adaptation strategies and show case studies for such strategies from both marine and freshwater environments.
Siegfried Roth - "The evolution of dorsoventral patterning in insects"
University of Cologne, Germany
Abstract: Toll-dependent patterning of the dorsoventral axis in Drosophila represents one of the best-understood gene regulatory networks. However, its evolutionary origin has remained elusive. Outside the insects Toll is not known for a patterning function, but rather for a role in pathogen defense. I will present our recent findings on the evolution of dorsoventral patterning in insects. In particular, I will describe our work on a hemimetabolous insect, the milkweed bug Oncopeltus fasciatus, whose lineage split from Drosophila’s more than 350 million years ago. In Oncopeltus, Toll is only required to polarize a dynamic BMP signaling network. Modeling of this network reveals that shallow Toll signaling gradients are sufficient to initiate axis formation. Dynamic BMP signaling combined with long-range, shallow Toll signaling gradients can explain the twinning of embryos upon egg fragmentation which has been observed in many insect lineages except the higher dipterans to which Drosophila belongs. Broad Toll signaling during early embryogenesis may also explain the emergence of Toll’s patterning function from a prior role in protecting the egg and embryo against microbial attacks.
Stefan Laurent - "Using population genetics and field experiments to study molecular evolution at Agouti: a gene underlying coat color adaptation in the Nebraskan deer mouse"
University of Lausanne, Switzerland
Abstract: Natural selection is widely accepted as the evolutionary force driving adaptation in natural populations, but in higher organisms, there are only a limited number of adaptive events that have been described not only at the phenotypic but also at the molecular and ecological level. One of these well-described adaptations is the evolution of cryptic coat color in the deer mice (Peromyscus maniculatus) living in the Nebraskan Sand Hills. In this region, a large field of dunes established around 10 to 15 thousand years ago and caused the color of the soil to become significantly lighter than the ancestral (and currently surrounding) darker soils. This change in substrate color is thought to have had dramatic consequences for dark-coated wild-type individuals because they are preys of visually-hunting predators. It has been hypothesized that by increasing their camouflage, light-coated mutants increase their fitness and that strong and recent positive selection, acting on the Agouti gene, is responsible for the correlation between substrate color and coat color observed in populations on and off the Sand Hills. In this talk I will present the results of population genomic analyses that improved our understanding of the selective sweep on Agouti and show that several mutations and recombination events contributed to this adaptive event. I will also present the results of a manipulative field experiment in which survival rates and genome-wide allele frequency changes (before/after predation) have been measured in controlled populations of dark and light populations on and off the Sand Hills. The results of this experiment highlight the reproducibility of positive selection on Agouti in this system. Finally, I will discuss statistical issues related to the analyses of this new type of temporal population genetic data.
Daniel Wegmann - "Inferring evolutionary processes from temporal and ancient data"
University of Fribourg, Switzerland
Abstract: Evolutionary change is the result of both genetic drift and selection, but disentangling these two processes has been proven difficult. Recent technological progress now hold promise to address this by looking at data from many individuals and the entire genomes. I will discuss recent statistical advances to make use of such new data and argue that power is maximized by investing into larger samples or over larger temporal scales, rather than the accuracy of individual samples. I will first discuss the potential of time series data to observe evolutionary change and introduce a novel method to jointly infer demography and selection from such data. As an example I will identify the loci conferring resistance to Influenza viruses that were evolved experimentally in the presence of Oseltamivir. Second, I will discuss statistical challenges along with solutions to include ancient DNA into evolutionary analysis to increase the temporal scale at which we quantify evolution of long-lived organisms such as humans. As an example I will discuss our latest insights into the spread of farming into Europe that we gained from sequences of the very first farmers in both the fertile crescent as well as the Aegean region. Interestingly, these data suggest that while farming spread from the Aegean mainly by the movement of people, it initially reach the shores of Europe by cultural diffusion.
Summer Semester 2016
Katja Räsänen - "Phenomics of maternally mediated adaptive divergence: insight from Rana arvalis and Salvelinus alpinism"
EAWAG Zürich, Switzerland
Abstract: Natural selection acts on the composite phenotype of organisms, meditated through a web of interactions between the external environment and genotype. One important source of phenotypic variation – especially at early life stages - are maternal effects, which can influence speed and direction of evolutionary responses and facilitate rapid local adaptation. Katja will focus on egg coats (maternally derived extra-embryonic membranes) as facilitators of adaptive divergence along an acidification gradient in the moor frog (Rana arvalis), and on egg size as facilitators of resource polymorphism evolution in sympatric arctic charr (Salvelinus alpinus). She will provide insight to the molecular and functional basis of these maternal effects, and emphasize that early life stage traits can play an important role in evolutionary diversification.
Tobias Uller - "Adaptive evolution of inheritance"
Lund University, Sweden
Abstract: Evolution by natural selection requires three conditions: variation between individuals, that some variants leave more descendants than others, and that offspring resemble their parents. The high-fidelity replication of DNA gives the impression that inheritance can be treated as a fixed channel of transmission. However, there is more to heredity than genes. Treating parent-offspring similarity as an evolving feature of life cycles allows us to address how mechanisms of inheritance change under natural selection. This sheds light on the adaptive evolution of a suite of transgenerational phenomena, from environmental maternal effects to incomplete epigenetic resetting. This perspective demonstrates that epigenetic and behavioural mechanisms can play several roles in evolution – from being a cause of phenotypic variation to enabling adaptive transgenerational plasticity and stable transmission of species-typical phenotypes.
Marc Naguib - " The evolution of communication: information flow in territorial animal societies"
Wageningen University, The Netherlands
Abstract: Many animals hold specific social relations to other individuals, like their mates, relatives, other group members, or territorial neighbours. To maintain such relations, communication is essential. Among such signals, advertisement signals are particularly interesting as they attract and repel others and are important in mating decisions and decisions to defend resources. To obtain information from such signals individuals often need move around to be in range of the signals, so that communication and spatial relations are strongly linked. This presentation will provide an overview over signalling, communication networks and spatial behaviour in animals, mainly using our long-term research on nightingales (Luscinia megarhynchos) and great tits (Parus major) as example. This includes also a current large-scale automatized radio-tracking project where we integrate social and communication networks to better understand the functioning on territorial animal societies.
Leonida Fusani - "The interplay between condition, food, and rest in migratory birds"
University of Vienna, Austria
Abstract: During migration, birds experience continuous changes in body condition. During long migratory flights over ecological barriers, such as deserts and seas, they use most of their energy stores. Therefore, birds spend a considerable amount of time at so-called stopover sites to refuel between flights. In the last decade, we studied the mechanisms controlling decision-making at stopover sites, that is, how birds decide whether they are ready to resume migration or not. Our work showed that when controlling for environmental factors, the extent of subcutaneous fat stores is the best predictor of the migratory disposition and in fact of the duration of the stopover. However, food has a strong effect on migratory behaviour, which is not necessarily linked to changes in body mass. As migratory birds literally eat their guts during migration, they need to rebuild their gastrointestinal tract before they can restore their energy reserves. This requires a fine control of activity patterns, because refuel occurs during the day whereas migration is mostly nocturnal. In this talk, I will present some highlights of our recent research on stopover physiology.