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 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 -
University of Fribourg, Switzerland
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.
Winter Semester 2015/2016
Beatriz Vicoso - "Frequent sex chromosome turnover in dipteran insects"
In many species, sex is determined by a pair of sex-chromosomes, such as the X and Y chromosomes of mammals. Although they originally arise from a pair of autosomes, X and Y chromosomes eventually acquire very specialized biologies. This is thought to prevent them from reverting to autosomes, so that the acquisition of differentiated sex chromosomes has been assumed to be an irreversible state.
Dipteran insects (flies, mosquitoes and midges) generally have XY sex chromosomes and a conserved karyotype, consisting of six chromosomal arms (5 large rods and a small dot). The XY pair of Drosophila melanogaster was assumed to be ancestral and shared by most Dipteran insects, an assumption supported by the apparent homology of the mosquito and Drosophila X-chromosomes.
Our genomic analysis of 37 species of Diptera shows that, contrary to this hypothesis, there is tremendous diversity of sex chromosome karyotypes in this group. First, we found that the X of Drosophila is not ancestral to Diptera. Instead, the ancestral X corresponds to the small “dot chromosome”, which then reverted to an autosome in Drosophila, demonstrating that such X to autosome reversals can happen. We also identified species with undifferentiated sex chromosomes, and others where a different chromosome replaced the dot as a sex chromosome, or where up to three chromosomes became incorporated into the sex chromosomes.
While surprising in itself, this diversity also allows us to test theories of sex chromosome evolution more systematically than was previously possible. Our multi-species transcriptome analysis shows that dosage compensation has evolved multiple times in flies, consistently through upregulation of the single X in males. However, X chromosomes generally show a deficiency of genes with male-biased expression, possibly reflecting sex-specific selective pressures. These species thus provide a rich resource to study sex chromosome biology in a comparative manner, and show that similar selective forces have shaped the unique evolution of sex chromosomes in diverse fly taxa.
Denis Reale - "Pulses resources and the ecology of eastern chipmunks"
UQAM, Montreal, Canada
Animal populations have to deal with temporal and spatial availability of resources. Pulsed resources represent an extreme case of resources fluctuation in a way that they are produced in huge amounts during restricted periods and are almost inexistent the rest of the time. Pulsed resources create a challenge to animals exploiting them, as these consumers have to find ways to adjust their life history in response to these fluctuations. This is the case of the eastern chipmunk (Tamia striatus) a small Sciurid commonly found in North-American forests, and that relies mainly on the American beech (Fagus grandifolia) in the northern regions of its distribution range. Once every 2-3 years, beech trees produce massive amounts of seeds, during what is generally called a masting even. Although eastern chipmunks can feed on different plants, small invertebrates, and other sources of food, they rely mostly on beech seeds for their reproduction and winter survival. Chipmunks store seeds into their burrow over the summer and the fall, and use these resources for their winter needs. Here we show the case of a chipmunk population in Southern Quebec that we have followed for 10 years. In this individually marked population we have collected information on individual burrow locations, habitat characteristics, behaviour, physiology, and genetics. Using this long-term data set we show how chipmunks life history and ecology depends strongly on beech seed fluctuations. Chipmunk reproductive cycles and population demography depend on masts; chipmunks do not reproduce every year, but concentrate their reproductive effort around masting events. Masts affect winter torpor, dispersal and the genetic structure of the population. Furthermore, because of the temporal fluctuation of seed production, chipmunks born at different cohorts show different life history strategies and personalities, and our results show cohort-dependent personality types fitted with specific life histories. Our results shed light on how fluctuation in ecological conditions may maintain personality differences and relationships between animal personality and life history.
Change of time and room : 15:00 -16:00 in G.00.001 Biocenter
Angela Hay - "Morphomechanical innovation drives explosive seed dispersal"
Abstract: How mechanical and biological processes are integrated across different scales to create complex traits is largely unknown. In this work, we combine biological, mathematical, and computational approaches to understand the mechanical basis for explosive seed dispersal - a key life history trait underpinning invasive behavior in the common weed Cardamine hirsuta. We have exploited the experimental tractability of C. hirsuta - a close relative of the model organism Arabidopsis thaliana – to understand the mechanism of explosive pod shatter and provide insights into the origin of this striking trait.
Krushnamegh Kunte - "Speciation and morphological diversification in Papilio swallowtail butterflies"
Abstract: The hallmark of life on earth is morphological diversity, which is often represented in spectacular sexually dimorphic and polymorphic phenotypes across species. I will address ecological pressures and genetic mechanisms that shape the evolution of morphological diversity with three stories of the iconic PapilioSwallowtail Butterflies. First, I will discuss the species radiation of Papilio in the geologically complex Indo-Australian Region, which has shaped reproductive isolation and speciation in Papilio as a function of biogeographic separation. Second, I will show how Batesian mimicry has driven wing pattern diversification, sexual dimorphism and polymorphism in Papilio. I will show that frequency dependent natural selection (predation) and sex-specific advantages of mimicry appear to have driven most of the wing pattern diversification in Papilio and related tropical butterflies. Finally, I will present the remarkable wing pattern polymorphism in Papilio polytes, which is an emerging genetic model system. Earlier I showed that doublesex, a transcription factor that regulates sexual differentiation in insects, also controls this female-limited mimetic polymorphism. I will present some recent work on the genetics of this polymorphism, which is beginning to characterize molecular variation in doublesex in nature. Thus, in this talk I will present a broad picture of the evolution of morphological diversification with respect to ecological and biogeographic processes, and its genetic and developmental regulation.
Amanda Bretman - "No fly is an island: how Drosophila respond to socio-sexual environments"
University of Leeds, UK
Abstract: We all modify our behaviour in different social situations to adapt, fit in or to become more competitive. Fruit flies also have complex social lives, aggregating independently of any resources, engaging in social learning, forming social networks and having a genetic propensity for different types of social environments. Using Drosophila melanogaster fruit flies as a model, we can investigate both the fitness consequences of changes of social environment and the mechanisms by which individuals can respond to such changes.
One aspect of the social environment that has a particular impact on males is how much mating competition (both before and after mating) they encounter. Theory predicts that if males can mate more than once they need to trade-off current and future mating opportunities, hence they should modify their mating effort at a particular mating depending on the amount of competition they face. Males of many species use plastic strategies to cope with this uncertainty, taking cues from the presence of other males or the mating status of females, and making adjustments to behaviour and ejaculate content accordingly. In D. melanogaster, after being exposed to a potential competitor, males mate for longer and transfer a higher quality ejaculate. This is has fitness benefits, at least in the short term, but is costly. By combining behavioural and life history data with transgenics and transcriptomics, we can investigate how such responses are coordinated and regulated, an important step in understanding how sophisticated, flexible social behaviours evolve. We are also starting to use this paradigm to investigate other consequences of social contact on traits such as ageing, immunity and cognition.
Jochen Blath - "On the role of dormancy in population genetics"
TU Berlin, Germany
Abstract: We analyse patterns of genetic variability of populations in the presence of a large seed bank with the help of a new coalescentstructure called the seed bank coalescent. This ancestral process appears naturally as scaling limit of the genealogy of large populations that sustain seed banks if the seed bank size and individual dormancy times are of the same order as the size of the active population. Mutations appear as Poisson processes on the active lineages, and potentially at reduced rate also on the dormant lineages. The presence of 'dormant' lineages leads to qualitatively altered times to the most recent common ancestor and non-classical patterns of genetic diversity. To illustrate this we provide a Wright-Fisher model with seed bank component and mutation, motivated from recent models of microbial dormancy, whose genealogy can be described by the seed bank coalescent. Based on our coalescent model, we derive recursions for the expectation and variance of the time to most recent common ancestor, number of segregating sites, pairwise differences, and singletons. The effect of a seed bank on the expected site-frequency spectrum is also investigated using simulations. Our results indicate that the presence of a large seed bank considerably alters the distribution of the site-frequency spectrum. Thus, one should be able to detect the presence of a large seed bank in genetic data.
Summer Semester 2015
Maria Anisimova-"Disentangling tandem repeats with computational prediction"
ETH Zürich, Switzerland
Abstract: Tandem repeats (TRs) are frequently observed in genomes across all domains of life. Evidence suggests that some TRs are crucial for proteins with fundamental biological functions, and can be associated with virulence, resistance and infectious/ neurodegenerative diseases. Genome-scale systematic studies of TRs have the potential to unveil core mechanisms governing TR evolution and TR roles in shaping genomes. However, TR-related studies are often non-trivial due to heterogeneous and sometimes fast evolving TR regions. In this talk I will discuss our recent contributions to computational and statistical approaches for TR annotation, TR-aware sequence alignment, and phylogenetic analyses of TR conservation. All these methods explicitly rely on the evolutionary definition of a tandem repeat as a sequence of adjacent repeat units stemming from a common ancestor. The discussed work has a focus on protein TRs, yet is generally applicable to nucleic acid TRs, sharing similar features.
Frank Oliver Glöckner - Environmental Bioinformatics - with a focus on “Marine”
Max Planck Institute for Marine Microbiology & Jacobs University Bremen gGmbH
Abstract: Investigations in molecular biology have transitioned from single experiments to high-throughput “big data” endeavours spearheaded by genomic sciences. New integrative approaches are needed to transform the wealth of environmental sequences and contextual (meta)data into biological knowledge on microbial diversity and function.
The talk will elaborate on the goals and perspectives of bioinformatics capacity building in the EU 7FP “Ocean of Tomorrow Project” Micro B3 (Marine Microbial Biodiversity, Bioinformatics, Biotechnology, www.microb3.eu). It will explain the concept, standards and implementation of the community driven Ocean Sampling Day (OSD, www.oceansamplingday.org). The first OSD took place worldwide on 21st of June (summer solstice) 2014, mobilizing over 190 marine sampling sites. The next OSD is planned for June 2015 with a strong involvement of citizen scientists (www.my-osd.org). These cumulative samples, fixed in time and space supplemented with a broad set of geo-referenced environmental parameters will provide new insights into the relationships between organisms, their genomic repertoire, and the environment surrounding them. Since most of the sampling sites are coastal, OSD provides the unique opportunity to study the effect of human pressure on the unseen majority in our ocean.
Jose Jimenez-Gomez- "Natural variation in circadian rhythms suggests effect of domestication on the circadian clock of tomato"
MPI Cologne, Germany
Abstract: The circadian clock controls many important aspects of plant physiology and development, including several traits of agronomical significance. Variation in circadian rhythms appears to be important for adaptation to specific environments. Domestication in tomato (Solanum lycopersicum) has drastically affected its geographical distribution and many characters of agricultural interest. I will show our work using tomato as a model system to study the importance of circadian rhythms during domestication.
Julian Glos - "Species and functional diversity of amphibian assemblages in a rainforest in Madagascar"
University of Hamburg, Germany
Abstract: Functional diversity illustrates the range of ecological functions in a community, and it allows revealing the appearance of functional redundancy in communities and processes of community assembly. Functional redundancy illustrates the overlap in ecological functions of community members which may be an indicator of community resilience. I will present patterns of species richness and species turnover, and of functional diversity and functional redundancy, in tadpole and frog communities in a rainforest of Eastern Madagascar. This habitat harbours one of the world's most species-rich amphibian communities. It is characterized by environmental changes and steep environmental gradients that are due to either natural changes (i.e., between two seasons) or anthropogenic impact (i.e., habitat fragmentation, disturbances). Accordingly, I will show how the patterns of species and functional diversity in amphibian assemblages vary along these environmental changes.
Ivan Gomez-Mestre- "Micro- and Macroevolution of Life Histories in Anurans:
Can Developmental Plasticity help Connect the Dots?"
Donana Biological Station, Spain
Abstract: Developmental plasticity allows populations to withstand rapid environmental changes and confers an overall faster rate of adaptation. However, selection in stable environments can result in genetic assimilation, potentially leading to trait divergence and species diversification. In that case, we would expect ancestral plasticity to mirror differences among taxa. Thus in that light, we are studying mechanisms of plasticity behind the evolutionary divergence of spadefoot toads. By studying the mechanisms of developmental acceleration in response to pond drying and comparing them across species, we have found that Pelobates tadpoles, which reflect the ancestral state of the group, increase their metabolic rate, and thyroid hormone and corticosterone concentrations in response to decreased water levels. All these parameters, however, seem to have been canalized in the descendant-state group Scaphiopus, leading support to the hypothesis of genetic accommodation.
Holger Goerlitz - "Auditory interactions in the night sky: bats, moths, and global warming"
Abstract: Echolocating bats and moths with bat-detecting ears interact in a predator-prey-relationship that is solely based on acoustic information. Bats use echolocation, an active-sensing strategy, to detect their insect prey. In turn, ears and evasive flight evolved in many insect taxa to prevent being captured by bats. We study these auditory-guided interactions between echolocating bats and eared moths in the field and lab, using neurophysiological recordings from moth ears, molecular diet analysis, flight path tracking in the field and acoustic modelling. This talk will present auditory adaptations in the prey to their sympatric predator ensemble, counter-measures in predators to avoid being heard by the prey, and additionally how external factors such as global warming might affect auditory interactions.
Winter Semester 2014/15
Clelia Gasparini - "Sex in the tank: what guppies can tell us about sexual selection and sexual conflict before and after mating"
The University of Western Australia, Perth, Australia
Abstract: Sex is rarely a harmonious process, and males and females often have conflicting evolutionary interests over reproduction. In most species such conflict rarely ends at mating because females typically mate with multiple males (polyandry), thus extending the opportunities for sexual selection to include sperm competition (where ejaculates from different males compete for fertilization) and cryptic female choice (where females moderate this competition). Using a small livebearing fish, the guppy, I study pre- and post- copulatory sexual selection to unravel strategies used by males and females to maximize their own reproductive success. In this seminar I will present results from my ongoing research that explores how these reproductive conflicts of interest play out across the sexual selection continuum (pre- and postcopulatory sexual selection). Insights from this work reveal how the females’ choice of attractive mates can be undermined by male behavioural strategies, how males make faster sperm to win the (sperm competition) race while ‘fussy’ females potentially counteract these effects by slowing them down, and ultimately why choosing the most popular male may yet pay off for females.
Robert Ptacnik - "Fresh and salty: Spatial pattern in plankton diversity along natural stress gradients"
WasserCluster Lunz, Austria
Abstract: Salinity represents about the strongest selective gradient in aquatic habitats, which is reflected in the distinctive biotas of freshwater and marine habitats. In estuaries, the transition from freshwater to marine conditions is populated by a few tolerant freshwater and marine taxa forming opposing ends of the gradient, plus a limited number of specialized brackish taxa. The brackish taxa, however, do not compensate for the species loss of other taxa. As a result, communities of most higher taxa exhibit a characteristic diversity minimum at intermediate salinities ('Artenminimum', Remane 1934).
This relationship can be understood regarding the limited connectivity among estuaries. It implies that the total species pool available for colonizing this intermediate zone is considerably smaller than the species pools populating its end points. Microscopic organisms are assumed to be highly mobile and at the same time expected to evolve rapidly. Salinity gradients therefore represent a test ground for the assumptions that biogeography of microbes differs fundamentally from higher organisms. I will show data on the spatial pattern of phytoplankton diversity in the Baltic Sea with a focus on the species pools and their origin that populate different salinities in the Baltic Sea.
Michal Kucera - "Cryptic diversity in marine plankton"
MARUM & Fachbereich Geowissenschaften, University of Bremen, Germany
Abstract: Species of marine eukaryotic plankton have numerically enormous populations, exposed to constant passive dispersal by currents that is not limited by physical barrier. Intuitively, these factors can be expected to inhibit speciation. Yet, marine plankton is highly diverse and, paradoxically, genetic fingerprinting has revealed that its biological diversity has been severely underestimated due to the abundance of cryptic speciation. Our research seeks to understand the nature and origin of cryptic species in the plankton and unravel the consequences for the study of biodiversity and evolution in the largest environment on the surface of the Earth. We use planktonic foraminifera, which produce one of the best fossil records available to study, allowing us to combine present-day phylogeography with the evolutionary history of the group. I will present the results from extensive global surveys of single-cell sequence data in three clades that revealed unexpected patterns of geographical and ecological structure in what previously seemed to be cosmopolitan species. Using well constrained molecular clocks, I will show that cryptic divergences are ancient and their existence reflects a fundamental de-coupling of morphological evolution from genetic divergence.
Marie Manceau - "Morphogenesis and Molecular Regulation of Colour Patterning in Natural Populations"
College de France, Paris, France
Abstract: The distribution of color across the body (i.e., color pattern) is a crucial morphological trait involved in survival and reproductive success which varies tremendously both within and between species. Despite their ecological importance, the genetic and developmental mechanisms responsible for the formation and variation of naturally-occurring color patterns have remained a black box. We showed that in deer mice (genus Peromyscus), the formation of a simple bicolor pattern typical of most vertebrates relies on the establishment of an embryonic “pre-pattern” (i.e., the spatial restriction of pigmentation genes) causing regional differences in pigment cell behavior. Moreover, we showed that large adaptive changes in the adult color pattern seen in a derived Peromyscus population are provoked by small accumulating changes in the pre-pattern. These findings laid the groundwork for studying (1) the embryonic origin of pre-patterns in the skin, (2) the molecular control of their formation and (3) the genetic basis of their evolution in other vertebrates groups. To this end, we propose to use analyses of gene expression and function in natural populations of birds displaying a vast array of skin patterns.
Julien Gagneur - "Insights from genetics of gene expression into mutational robustness and causal inference."
LMU Genzentrum, Munich, Germany
Abstract: I will present two of our systems genetics studies.
1. Mechanisms conferring robustness against regulatory variants have been controversial. Previous data suggested widespread buffering of RNA misexpression on protein levels during translation. We do not find evidence that translational buffering is common. Instead, we find extensive buffering at the level of RNA expression, exerted through negative feedback regulation acting in trans, which reduces the effect of regulatory variants on gene expression.
2. We show how non-additive effects between genotype and environment can be exploited for causal inference in molecular networks. Using genome-wide perturbation assays in yeast, we experimentally demonstrate the validity of the approach.
Andrea Betancourt - "Transposable element dynamics in Drosophila”
VedMedUni Vienna, Austria
Abstract: Transposable elements are genomic parasites with an evolutionary strategy of increasing their copy number; the success of this strategy can be seen in many eukaryotic genomes, which contain large fractions of transposon derived DNA. Recently, we have begun to acquire an in-depth picture of the population dynamics of transposable elements in Drosophila, with both bursts of transposition and purifying selection against new insertions appear to affect population frequencies of insertions. However, another important process in transposable element evolution -- horizontal transmission between species -- is less wellunderstood. The classic example of a horizontally transmitted element is that of the P-element in D. melanogaster. Recently, we have found that the P-element appears to have recently spread from D. melanogaster into a sister species, D. simulans. P-element appears to have spread quickly in D. simulans, with strains from the same geographic region showing P-element to have increased from low to high frequency within a decade.
Brian Hollis - "Adaptation and antagonism in populations evolving without sexual selection"
University of Lausanne, Switzerland
Abstract: Sexual selection may accelerate adaptation, as "good genes" theory predicts, or act as a load upon populations because of conflict between the sexes. We investigate these possibilities with fly populations that have evolved in the laboratory for over 150 generations either with sexual selection (a polygamous mating system) or without sexual selection (a monogamous mating system). Monogamous populations benefit from the evolution of reduced sexually antagonistic interactions, which can be detected in the female post-mating transcriptional response. Male selection pressures are also greatly relaxed under monogamy. This has resulted in the evolution of feminized patterns of gene expression, suggesting strong constraints on sexually dimorphic gene expression in nature.
*Brian Hollis will be available to meet with first year EES students on Jan 19th at 15:00*
Wolfgang Stephan - "Population genomics of adaptation in Drosophila melanogaster"
Abstract: In several organisms (whose genome has been sequenced) scans of DNA sequence variation have been carried out to elucidate the recent demographic and adaptive histories of these species. Using selective sweeps, it is possible to identify adaptive events in the genome. I will present results from our work on Drosophila melanogaster. I show that selective sweep analysis can be used to accurately map targets of positive selection in the genome. Furthermore, I will discuss whether selective sweep mapping can be combined with QTL mapping to determine the phenotype selection has been operating on. Two case studies will be highlighted: (1) the divergence of the tandemly duplicated polyhomeotic (ph) genes under positive selection, and (2) the localization of candidate genes for cold tolerance.
Summer Semester 2014
Miltos Tsiantis - "From genes to geometry: towards understanding development and diversification of leaf form"
MPI for Plant Breeding Research, Cologne, Germany
Abstract: A key challenge in biology is to understand how diversity in organismal form is generated. Genetic analyses in model systems have identified key regulators that sculpt the body plans of metazoa and seed plants. However, less is known about how the action of such regulators produces particular organ shapes, or how the balance of conservation versus divergence of such form regulating pathways generated the tremendous morphological diversity of multicellular eukaryotes. One impediment to answering these questions is the relative paucity of experimental platforms where genetic tools can be utilized to unambiguously study morphogenesis and its evolution in a genome-wide, unbiased fashion. To circumvent this problem we developed the Arabidopsis thaliana relative Cardamine hirsuta into a versatile system for studying morphological evolution. We aim to understand the molecular mechanisms through which leaf morphology evolved in these species, resulting in simple, undivided leaves in A. thaliana and dissected leaves with distinct leaflets in C. hirsuta. This presentation will discuss our progress towards understanding the genetic pathways that specify dissected versus entire leaf shapes and that regulate the number, position and timing of leaflet production.
Jonathan Jeschke - "What we know and don’t know about invasive species and other novel organisms"
Technical University of Munich, Germany
Abstract: The talk will consist of two parts, the first one focusing on invasive species and the second one on other types of novel organisms, e.g. range-expanding species, GMOs, or emerging pathogens. I will start with an overview of current understanding, and lack thereof, about invasive species. The focus will be on animals, but comparisons to plants and other organisms will be made as well. I will address the following fundamental questions about biological invasions: (1) How many species become invasive in a given region? (2) Which ecosystems are especially susceptible to invaders? And (3) What are the long-term effects of invaders? In the second part of the talk, I will present a framework that compares invasive species with other types of novel organisms, e.g. emerging pathogens, and allows knowledge transfer among researchers and managers working on different novel organisms.
Gerald Wilkinson - "Sexual selection, genomic conflict and speciation in stalk-eyed flies"
University of Maryland, USA, and Wissenschaftskolleg zu Berlin, Germany
Abstract: Speciation occurs when isolated populations diverge sufficiently to cause reproductive isolation. The processes that drive such divergence remain poorly understood. One possibility is sexual selection, which can cause rapid evolution of traits that influence precopulatory or postcopulatory success, but should only cause divergence if populations exhibit differences in mating preferences. An alternative is some type of genomic conflict, such as that responsible for biased transmission of X or Y-bearing sperm, that leads to an arms race between driving and suppressing elements. If coevolution among elements proceeds independently in isolated populations, then heterogametic hybrid sterility or inviability could occur. In this talk, I will present results from a series of studies on stalk-eyed flies that show how sexual selection and genomic conflict operate and interact to cause rapid evolution of reproductive isolation among allopatric populations in southeast Asia. I will also discuss recent genome and transcriptome studies that provide insight into the genetic causes and consequences of the ongoing sex chromosome conflict. The results suggest the genomic landscape, especially of the sex chromosomes, is remarkably dynamic in this extraordinary group of flies.
Gerald Schneeweiss - "Phylogeny and evolution of the non-photosynthetic parasitic broomrapes (Orobanchaceae)"
University of Vienna, Austria
Abstract: A hallmark of plants is their ability to utilize light as the primary energy source for producing complex organic compounds. Some plants, however, developed deviating nutritional modes including parasitism, which within angiosperms has independently evolved about twelve times. A major lineage of parasitic angiosperms is the family Orobanchaceae, containing c. 2000 species, where the full range of nutritional modes from non-parasitic via facultative and obligate photosynthetic parasites (hemiparasites) to non-photosynthetic parasites (holoparasites) is realized, rendering Orobanchaceae the model group for studying genetic, genomic, physiological and morphological adaptations and changes associated with the shift to and the intensification of parasitism. Here, I will focus on the exclusively holoparasitic clade containing Orobanche and related genera to address phylogenetic-taxonomic and evolutionary questions with respect to, for instance, genome or life history evolution.
Christian Sturmbauer - "Adaptive evolution and phenotypic plasticity in the context of adaptive radiation"
Department of Zoology, University of Graz, Graz, Austria
Abstract: Allopatric speciation often yields ecologically equivalent sister species, so that their secondary admixis enforces competition under sympatry. The rocky shores of Lake Tanganyika harbor more than 100 distinct populations and sister species of the cichlid genus Tropheus, but only some are sympatric. When alone Tropheus occupies a relatively broad depth zone, but in sympatry fish segregate by depth. To assess the effects of competition we studied the partial co-occurrence of Tropheus moorii “Kaiser” and “Kirschfleck” with Tropheus polli along a section of the central eastern shores of the lake. Hybridization experiments demonstrated that some observed differences between Tropheus “Kaiser” living alone and in sympatry to T. polli have a genetic basis despite large-scale phenotypic plasticity. Using geometric morphometrics and neutral genetic markers, we investigated whether sympatric populations differ consistently in body shape from populations living alone and if the differences are adaptive. We found significant differences in mean shape between non-sympatric and sympatric populations, whereas all sympatric populations of both color morphs clustered together in shape space. Sympatric populations had a relatively smaller head, smaller eyes, and a more anterior insertion of the pectoral fin than non-sympatric populations. Genetically, however, non-sympatric and sympatric “Kaiser” populations clustered together to the exclusion of “Kirschfleck”. Genetic distances, but not morphological distances, were correlated with geographic distances. Within- and between-population covariance matrices for T. moorii populations deviated from proportionality. We conclude that natural selection acts on both phenotypic plasticity and heritable traits, and that both factors contribute to the observed shape differences. The consistency of the pattern in five populations suggests ecological character displacement.
Fabian Staubach - "Approaches to better understand the role of microbes in the adaptation of metazoans"
University of Freiburg, Germany
Abstract: Almost all organisms on earth are associated with microorganisms. These microorganisms are important for the evolution of their hosts. However, the role they play for the evolution of their hosts can be very different. On the one hand, disease causing pathogens can exert strong selection pressures on the host that are reflected by fast evolution of host immune genes. On the other hand, microbes that are beneficial for the host have facilitated major adaptations of their host. A prominent example of an adaptation through microorganisms is the protistan microbiota in the gut of termites that facilitates the digestion of wood. I will present approaches to better understand the role of microbes in adaptation using Drosophila and termites as models.
Gerton Lunter - "Inferring demography from whole-genome data"
University of Oxford, UK
Abstract: Genetic data is informative about demography, and holds for instance evidence of past population bottlenecks, admixture and migration. Inferring these from genetic data is however not trivial. Most existing approaches rely on summary statistics, such as site-frequency spectra. More recently, approaches that directly model the process of recombination and coalescence along the sequence have succeeded in inferring past population changes from a single diploid genome. However, extending this approach to multiple samples is not straightforward.
In the talk I will discuss an approach we have been taken, using a fairly recent statistical technique known as particle filters. This approach has the promise to scale to high-dimensional models, and is well suited to this particular inference problem.
Detlev Arendt - "Evolution of the central nervous system in Bilateria"
EMBL Heidelberg, Germany
Abstract: We are intrigued by one of the great remaining mysteries in animal evolution: how did our central nervous system (CNS) come into existence? What did it look like at first and how did it function? We are especially interested in the CNS of an extinct animal known as Urbilateria, the last common ancestor of humans, flies and most other ‘higher’ animals that live today, which lived some 600 million years ago in the ocean. Our lab has chosen to investigate a new molecular animal model, the marine annelid Platynereis dumerilii. As a ‘living fossil’, Platynereis represents an ideal connecting link between vertebrates and the fast evolving protostome models, Drosophila and Caenorhabditis. Genomic resources and molecular techniques have been generated that make it a model marine invertebrate for ocean biology and for organismal systems biology. As characteristic for the Platynereis life cycle with different stages exploring different ecological niches, environmental influences impact directly on the organismal state (eco-devo) or are sensed via the nervous system (organismal neurobiology) and are reflected by the variation on genome, transcriptome or any other level of the cellome.
Miguel Gallach - "Recurrent turnover of chromosome-specific satellites in Drosophila"
Abstract: Non-coding repetitive DNA has the ability to adopt specific folding structures that may help cells identify chromosomes. In addition, repetitive DNA elements have also become a major interest among evolutionary biologists since species-specific interactions between chromatin remodeling proteins and repetitive DNA elements are disrupted in hybrids. Remarkably, in Drosophila, the X and dot chromosomes are identified by chromosome-specific binding proteins and they are particularly involved in genetic incompatibilities between closely related species. I found that these two chromosomes are overpopulated by certain repetitive elements that undergo recurrent turnover in Drosophila species. The biology and evolutionary patterns of the characterized satellites suggest that they provide both chromosomes with some kind of structural identity and are exposed to natural selection. The rapid satellite turnover fits some speciation models and may explain why these two chromosomes are typically involved in hybrid incompatibilities
Winter Semester 2013/14
John Colbourne - "How Genomic Responses to the Environment Vary"
Environmental Genomics Group, School of Biosciences, University of Birmingham, UK
Abstract: Daphnia, or the water flea, is a sentinel species of freshwater ecosystems. Their populations are defined by the boundaries of ponds and lakes, are sensitive to modern toxicants in the environment, and thus are used to assess the ecological impact of environmental change. Their short generation time, large brood sizes, and ease of laboratory and field manipulation have assured Daphnia’s importance for setting regulatory standards by environmental protection agencies, testing chemical safety, monitoring water quality, and as a model for environmental genomics research. In this study, we take advantage of the animal’s clonality and mature genomics tools to dissect the sources of gene expression variation in the stress response of genetic isolates to six environmentally relevant pollutants, and their binary mixtures. One isolate originates from a natural population that has faced severe chemical challenges for over a century of industrial iron/ore smelting and thus demonstrates evolved tolerance to toxic levels of certain metals. Another isolate originates from a population that has no history of chemical stress and is clearly harmed by metal exposure. By interrogating differential expression of 31,000 annotated genes from 50 comparisons across conditions and between isolates, the current study provides new insights into the functional interactions among genes and environment.
The research was conducted during hands-on training in “Environmental Genomics” – an annual summer course offered at the Mount Desert Island Biological Laboratory.
Alexandre Courtiol - "What can humans tell us about mate choice in other species?"
Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
Summary: My talk aims at demonstrating that anthropocentrism is a flaw that can be turned into an asset. Keeping humans in mind can indeed help us to better understand animal behaviour and working on humans allows researcher to gather data that are difficult to collect in other organisms. I will rely on the work I performed on mate choice in humans to illustrate this claim. I will show you how some trivial observations of our everyday life has lead me to rethink the theory of sexual selection. In short, I will explain why humans could be considered as a model organism for the study of mate choice.