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.
Summer Semester 2018
Martin Kapun - Clines and inversions as evidence for local adaptation in Drosophila melanogaster
University of Fribourg, Switzerland
Abstract: Clines, which are gradual changes of genotypes or phenotypes along environmental transects, are often taken as prima facie evidence for the action of spatially varying selection. However, only due to recent advances in sequencing technology it now becomes possible to compare genome-wide clinal patterns and test for alternative models. We use the Drosophila melanogaster system to study genomic diversity along a latitudinal temperature gradient at the North American east coast. We found evidence for steep and temporally stable clinal variation associated with In(3R)Payne, a common cosmopolitan inversion, that cannot be explained by demography alone. To learn more about the potential adaptive effect of this inversion, we compare karyotype-specific genomic and transcriptomic variation on different continents. We find genomic regions in the center of the inversion that are in strong linkage disequilibrium with the inversion breakpoints possibly as a result of selection for inversion-specific genetic variation. Finally, with the help of a newly founded population genetics consortium, we now expand the genome-wide analysis of clinal genomic variation to the yet largely unexplored European continent and find further evidence for the clinal variation of In(3R)Payne despite complex demographic patterns.
Dieter Heylen - Evolutionary ecological interactions between songbirds, ticks and Borrelia burgdorferi s.l.: a community perspective
University of Antwerp, Belgium
Abstract: Dieter Heylen is postdoctoral at the University of Antwerp (Biology department, Evolutionary Ecology group). He has more than ten years of experience in the study of ticks, songbirds and tick-borne diseases (TBD). He studies how the evolutionary ecology of host-parasites interactions relates to virulence, ecological specialization, adaptation, and spatio-temporal occurrence of ticks and TBD in songbirds. In more recent work, he investigates how ticks and birds contribute in the maintenance and establishment of TBD foci, by studying the reservoir competence of songbird species, and the vector-competence of bird-specialized tick species. He currently investigates how landscape determines TBD transmission flows over urbanisation gradients, and how isotope ratios of ticks can help in
elucidating transmission dynamics in the wild. In his seminar, he will consider the findings on the ecological interactions between ixodid ticks, common European songbirds and the Lyme disease causing bacteria Borrelia burgdorferi s.l..
Chris Jiggins - Understanding porous species boundaries by studying butterfly genomes
University of Cambridge, UK
Abstract: A major undertaking in evolutionary biology is to link genotype to phenotype and understand the evolutionary changes that lead to adaptation and speciation. Here I will give an overview of our work on the brightly coloured Heliconius butterflies, showing that hybridisation makes species boundaries remarkably porous across the genome. Patterns of species relationships are highly variable across the genome, and this can offer insight into the process of speciation. There is little evidence for changes in recombination rate or inversion differences between species during speciation. Despite these loci of large effect, across the genome there is evidence for pervasive polygenic selection maintaining species differences in the face of ongoing gene flow, indicated by a strong association of admixture with regions of high recombination.
Gergely Szollosi - Gene transfers, like fossils, can date the tree of life
University of Budapest, Hungary
Abstract: The geological record provides the only source of absolute time information to date the tree of life. But most life is microbial, and most microbes do not fossilize, leading to major uncertainties about the ages of microbial groups and the timing of some of the earliest and most important events in life's evolutionary history. I discuss our recent results, which show that patterns of lateral gene transfer deduced from analysis of modern genomes encode a novel and highly informative source of information about the temporal coexistence of lineages throughout the history of life. We use new phylogenetic methods to reconstruct the history of thousands of gene families and show that dates implied by gene transfers are strongly correlated with estimates from relaxed molecular clocks in Bacteria, Archaea and Eukaryotes. A comparison with mammalian fossils shows that gene transfer in microbes is potentially as informative for dating the tree of life as the geological record in macroorganisms.
Rodrigo Medellin - How to do conservation science, implement it, and not die trying.
Instituto de Ecología, UNAM, Mexico
Abstract: Conducting research for conservation is, unfortunately, too often cut short or rarely implemented. I will discuss a few examples of research projects that have become official federal government programs with nation-wide implications. Mexico is the fifth country with the greatest biodiversity in the world. Challenges are thick and plentiful. Recently Mexico became the first country in the world to have an estimate of how many jaguars inhabit the country and the National Jaguar Strategy is fully in place and being implemented today. I will also speak about bighorn sheep and how a sustainable harvest has become the heart and soul of a strong conservation and development program for the Seri indigenous group. Bats represent about one-fourth of Mexico’s mammals and they include critically endangered and endangered species. The lesser long-nosed bat has been a focal species for my research and after 25 years it was recently delisted from Mexico’s Endangered Species List. The recovery implied lots of research, education, and specific conservation actions. The job of conservation professionals must include working with government and public to be effective.
Tuncay Baubec - Function and regulation of mammalian DNA methylation
University of Zurich, Switzerland
Abstract: DNA methylation is a prevalent epigenetic modification involved in transcriptional regulation and essential for mammalian development. In mammalian genomes, DNA methylation is a prevalent modification that decorates the majority of cytosines. It is found at the promoters and enhancers of inactive genes, at repetitive elements, and within transcribed gene bodies. Its presence at promoters is dynamically linked to gene activity, suggesting that it could directly influence gene expression patterns and cellular identity. While the genome-wide distribution of this mark has been studied to great detail, the mechanisms responsible for its correct deposition, as well as the cause for its aberrant localization in cancers, have not been fully elucidated. I will present our recent efforts to elucidate the targeting preferences of DNA methyltransferases to the genome, and how chromatin states, histone modifications and DNA sequence help to guide deposition of DNA methylation to specific genomic sites.
Homa Papoli - The evolution of sex chromosomes and sex-linked sequences in systems with female heterogamety
Uppsala University, Sweden
Abstract: Sex chromosomes evolved from a pair of autosomes between which recombination stopped. We can look at sex chromosome evolution at two levels. The first is looking at a large evolutionary time scale to investigate the steps involved in recombination cessation. In another level, we can look at the consequences of recombination cessation in the evolution of sex linked sequences. We used ostrich, as a representative of a basal clade of birds, together with several avian species to infer the chromosomal inversions involved in the evolution of sex chromosomes. To understand the consequences of recombination suppression on the evolution of DNA sequences, we used multiple avian species and a population level data of ostrich sex chromosomes to infer determinants of genetic diversity.
Thomas Gilbert - Dogs and Wolves in Time and Space
University of Copenhagen, Denmark
Abstract: Despite the key position that dogs hold in the lives of many of us, and the extensive efforts of many previous scientific studies, a surprising amount remains to be learnt about our faithful friends. For example, considerable controversy exists over such basic questions as: When did we first domesticate the dog? Where was the domestication centre? Was there more than one? And perhaps most surprisingly, what was the dog even domesticated from? Given the extent to which we have both moved and shaped dog breeds in recent centuries, and taken a good stab at eradicating their wild relatives, it seems unlikely that analyses of modern genetic material alone will be able to solve these questions. As such deciphering dog domestication represents an exciting frontier on which palaeogenomic approaches stand to make enormous contribution, and indeed, in light of a vastly expanded reference dataset of contemorary genomic material, a number of intriguing findings are already coming to light.
Winter Semester 2017/2018
Samantha Patrick - Life history correlates of consistency and variability in behaviour
University of Liverpool, UK
Abstract: How individuals obtain the resources they need for survival and reproduction is integral to their fitness. Individuals may differ in the way in which they search for food or the spatial and temporal consistency in their foraging strategy. The fitness consequences of short and long term consistency are poorly understood and whether differences within populations emerge due to adaptive strategies or constraints linked to quality has rarely been studied. In this presentation I will discuss the emergence of individual differences in the exploration-exploitation trade off, indicative of differences in searching behaviour. I will present evidence of short and long term consistency in foraging area and habitat choice and examine whether specialists and generalist coexist or whether specialisation is always adaptive. I will look at how these foraging traits change over the lifetime of individuals and reveal the importance of intrinsic drivers in shaping the links between foraging and fitness.
Katie Peichel - Genetics of adaptation in sticklebacks: the roles of pleiotropy and linkage
University of Bern, Switzerland
Abstract: Despite recent progress, relatively little is known about the specific genetic and molecular changes that underlie adaptation to new environments. Stickleback fish have been at the forefront of research to uncover the genetic and molecular architecture that underlies adaptation and speciation. A wealth of quantitative trait locus (QTL) mapping studies in sticklebacks has provided insight into the distribution of effect sizes during adaptation and has also revealed that several regions of the genome contain more loci than expected for traits involved in adaptation. It is unknown whether these trait clusters result from tight physical linkage of multiple genetic changes responsible for different traits, or from a single genetic change with pleiotropic effects. I will discuss recent research in my group that is focused on disentangling the roles of pleiotropy and linkage in adaptation, using both genome-wide approaches and more focused studies of specific loci with a major effect on adaptation.
Christian Schlötterer - Evolution of gene expression in Drosophila
VedMedUni Vienna, Austria
Abstract: Temperature is a major environmental factor affecting many traits, including gene expression. While at benign temperatures the gene expression pattern is very similar between genotypes, at more extreme temperatures large genotype specific differences can be detected. Most of the differences in expression can be attributed to trans-effects. Nevertheless, it is not apparent to what extent these differences in gene expression reflect adaptive responses. We address this question by exposing a natural Drosophila population to new temperature environments and study the change in gene expression after more than 60 generations of experimental evolution. We show that the ancestral plasticity in natural Drosophila populations is most likely adaptive, because after 60 generations most of the ancestrally plastic genes increased their plasticity at the extreme laboratory environments.
Daniel Hooper - Chromosome inversions and avian speciation
Cornell University, USA
Abstract: Species divergence is associated not just with the accumulation of molecular changes in DNA composition but oftentimes also with structural changes to the genome, such as chromosomal inversions. Because the speciation process is protracted, it appears that gene flow among incipient species is common and may often influence the generation of reproductive isolation. While gene flow generally acts to homogenize differences between diverging populations it can, paradoxically, play a creative role in speciation by promoting the evolution of chromosome inversions that encompass and keep together sets of locally adapted genes. Chromosome inversions commonly distinguish the genomes of closely related bird species and are increasingly found as polymorphisms within species. Why? I will first share results from a pair of comparative studies on inversion evolution using cytological data from more than 400 species in the most speciose order of birds, the
passerines, in order to test support for alternative models of inversion fixation (1,2). Secondly, I will share results from an ongoing project examining the extent to which chromosome inversions contribute to reproductive isolation in an avian hybrid zone.
1. Hooper, D. M. & T. D. Price. Rates of karyotypic evolution in Estrildid finches differ between island and continental clades. 2015. Evolution 69:890-903.
2. Hooper, D. M. & T. D. Price. Chromosomal inversion differences correlate with range overlap in passerine birds. 2017. Nature Ecology & Evolution 1:1526-1534.
Jonathan Jeschke - Hierarchies of hypotheses and other new tools for research synthesi
Freie Universität Berlin, Germany
Abstract: Massive amounts of ecological and other data are accumulating each year. In the current era of Big Data, the statement by Naisbitt that “we are drowning in information but starved for knowledge” from the 1980s seems to be more applicable than ever before. We arguably lack effective tools for research synthesis at a macro level, tools that help “connect the dots.” I will present new synthesis tools – Hierarchies of Hypotheses (HoHs), networks of major hypotheses and research questions, among others – and give examples for applications of these tools in invasion ecology and biogeography.
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.
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.
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”.
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.