EES seminars 0708
Tuesday Seminar Series in Ecology, Evolution and Systematics
The EES program has its own seminar series. The organizers for this year are Aurélien Tellier, Stefan Laurent and Pleuni Pennings. If you would like to meet with one of the speakers while they are here, of if you have suggestions for speakers for next semester, please talk to one of us.
Department Biologie II LMU BioZentrum, Grosshaderner Strasse 2 82152 Planegg-Martinsried
- link to EES Seminars 0809
All seminars will be held in Room B 01.019 (Hörsaal 1) from 17.00 until 18:00
15/04/08 Prof Dr Michael NACHMAN
Department of Ecology and Evolutionary Biology, University of Arizona
Title: The genetic basis of adaptation and speciation in mice
Adaptive changes within species and the origin of new species constitute the two major features of evolution. Finding the genes underlying these processes is a major challenge for evolutionary genetics. I will present recent work from my lab on the genetic basis of adaptive coat color variation in pocket mice and on the genetic basis of reproductive isolation in house mice. Rock pocket mice are typically light and live on light-colored rocks. In several places, however, dark mice have evolved on dark lava flows as an adaptation against predation. Association studies and genetic crosses have identified the genes underlying this adaptation and demonstrated that dark mice have evolved independently in different populations through changes at different genes. House mice in the genus Mus consist of young species that hybridize in nature and are isolated by hybrid male sterility. Laboratory crosses show that the X chromosome play a key role in reproductive isolation. Hybrid sterility has a surprisingly complex genetic basis, despite the fact that these species are recently diverged.
29/04/08 Prof Dr Laurent EXCOFFIER
Zoology Institute, University of Bern
Title: Statistical evaluation of models of human evolution
An appropriate model of recent human evolution is not only important to understand our own history, but it is necessary to disentangle the effects of demography and selection on genome diversity. Although most genetic data support the view that our species originated recently in Africa, it is still unclear if it completely replaced former members of the Homo genus, or if some interbreeding occurred during its range expansion. Several scenarios of modern human evolution have been proposed on the basis of molecular and paleontological data, but their likelihood has never been statistically assessed. Using DNA data from 50 nuclear loci sequenced in African, Asian and Native American samples, we show here by extensive simulations that a simple African replacement model with exponential growth has a higher probability (78%) as compared with alternative multiregional evolution or assimilation scenarios. A Bayesian analysis of the data under this best supported model points to an origin of our species approximately 141 thousand years ago (Kya), an exit out-of-Africa approximately 51 Kya, and a recent colonization of the Americas approximately 10.5 Kya. We also find that the African replacement model explains not only the shallow ancestry of mtDNA or Y-chromosomes but also the occurrence of deep lineages at some autosomal loci, which has been formerly interpreted as a sign of interbreeding with Homo erectus
13/05/08 Prof Dr Brian CHARLESWORTH
Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh
Title: The evolution of Y chromosomes
Sex in many higher organisms is determined by a pair of genetically and structurally distinct chromosome, the X and Y chromosomes. In the heterogametic (XY) sex, these fail to cross over with each other over most or all of their length, whereas crossing over is normal in the homogametic (XX) sex, This means that the Y chromosome is maintained permanently heterozygous, in the almost complete absence of genetic recombination. This makes it a unique component of the genome. These properties are associated with the degeneration of Y chromosomes: they usually have very few active genes, and contain a large quantity of repetitive DNA, although there is strong evidence that the X and Y were originally largely identical in content. Population genetic processes that lead to the degeneration of the Y are described, with especial emphasis on the evolutionary consequences of lack of recombination. Two model systems for testing the predictions of the population genetic models are described. The first is the neo-Y chromosome of Drosophila miranda, which evolved from an autosome that became joined to the Y chromosome, and hence is inherited in the same way. The second is the newly-evolved Y chromosome of the plant Silene latifolia and its relatives. Studies of DNA sequence variation and evolution in these two systems will be presented, which shed light on the evolutionary forces that have caused Y chromosome degeneration.
27/05/08 Prof Dr Manfred MILINSKI
Department of Evolutionary Ecology, Max-Planck-Institute for Evolutionary Biology
Title: The evolutionary economy of human cooperation. Can we rescue the global climate?
The problem of sustaining a public resource that everybody is free to overuse emerges in many social dilemmas. We obviously overuse public goods, e.g., by over fishing oceans, driving pension and health insurance systems to bankrupt or risking the collapse of the global climate through unlimited use of fossil energy. These are showpieces of the 'tragedy of the commons', for which Hardin envisaged only inevitable breakdown. Public goods experiments, i.e. the experimental paradigm to study such problems, usually confirm that the collective benefit will not be produced. Because individuals and countries often participate in several social games simultaneously, the interaction of these games may provide a sophisticated way by which to maintain the public resource. Indirect reciprocity, 'give and you shall receive', is built on reputation and we found that it can sustain a high level of cooperation. In collaboration with the MPI for Meteorology we applied this approach to test whether humans are willing to invest in sustaining the global climate and found surprising results.
10/06/08 Prof Dr Armin MOCZEK
Indiana Molecular Biology Institute, Center for Integrative Study of Animal Behavior & Program in Cognitive Sciences
Title: On the origins of novelty in development and evolution: a case study on beetle horns
Evolutionary biology offers several frameworks for understanding how complex traits may be modified over evolutionary time. However, we know remarkably little about how such traits might originate in the first place. What are the genetic, developmental, and ecological mechanisms, and the interactions between them, that mediate not just the modification of existing traits, but the origin of novel traits and trait diversity? In my talk I explore the genetic, developmental, and ecological underpinnings of a class of traits that is both novel and highly diverse: beetle horns. Several thousand species of beetles express horns, and dramatic variation in size, location, shape, and number of horns exist both within and between species. Most importantly, beetle horns lack obvious homology to other insect traits, instead they can be viewed as a novel feature that horned beetles invented during their evolutionary history, and which has since undergone one of the most dramatic trait radiations in the animal kingdom. Using a combination of morphological, developmental, genetic and genomic studies I explore the evolutionary origins of horns, as well as the mechanisms that mediated the subsequent diversification of horn expression across species.
24/06/08 Dr Sylvia CREMER
Evolution, Behavior and Genetics Dpt, University of Regensburg
Title: Social immunity in ants
Abstract: Living together in groups increases the risk of disease transmission, as individuals live together in close densities and are often closely related. In groups of temporarily crowding solitary individuals, such as the migratory locust and some butterfly larvae, individuals try to counteract this increased risk by a higher investment into individual immunity. Contrary to this, members of social groups, such as the colonies of social insects, protect themselves by a collective investment into colony-level immunity. These social immune systems comprise both the physiological immune systems of all group members and their cooperatively performed hygienic behaviours. I study the interaction between healthy and diseased individuals in ant colonies, and the risks and potential benefits of performing hygienic behaviours.
08/07/08 Prof Dr Dieter EBERT
University of Basel, Switzerland
Title: Antagonistic coevolution
Parasites are assumed to evolve to optimise their exploitation of hosts, while hosts evolve to minimize the damage done by the parasite. In coevolutionary models of this process high specificity in host parasite interactions are assumed. These interactions result in rapid response to selection, i.e. genotype frequency changes within a few host generations. In the Daphnia system this can be conveniently addressed experimentally. In my talk I present experiments, which we undertook to understand the shape of antagonistic coevolution. In particular I will try to disentangle the outcomes of models based on selective sweeps and models based on negative frequency dependent selection. I show that host-parasite interactions are indeed highly specific and that populations evolve rapidly in response to parasite mediated selection and that hosts and parasite coevolve. Combined these results are more consistent with a model based on negative frequency dependent selection than a model based on selective sweeps. Experiments are conducted with the Daphnia magna - Pasteuria ramosa system. D. magna reproduce clonally in the laboratory with a generation time of only 10 days. Populations can be easily studied in the laboratory and under field conditions, so that epidemiological aspects of host-parasite interactions can be considered. P. ramosa is a fast evolving endospore forming bacterium.
Carius, H. J., Little, T. J. and Ebert, D. (2001). "Genetic variation in a host-parasite association: Potential for coevolution and frequency-dependent selection." Evolution 55(6): 1136-1145.
Decaestecker, E., Gaba, S., Raeymaekers, J. A. M., Stoks, R., Van Kerckhoven, L., Ebert, D. and De Meester, L. (2007). "Host-parasite 'Red Queen' dynamics archived in pond sediment." Nature 450: 870-U16.
- For more seminar to come in the Winter Semester 0809 see EES Seminars 0809