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I am an evolutionary biologist with a fascination for the causes and consequences of individual variation. In my research, I aim at disentangling the role of genes and the environment in shaping this variation, and to test for its consequences in terms of individual-level fitness and population-level structure and demography. Using a combination of theoretical and empirical work, my research aims at advancing our understanding of the individual- and population-level consequences of environmental change. To this end, I combine ideas and techniques from population, quantitative and molecular genetics, as well as life-history theory, and apply these to large-scale (individual-based) datasets.

prospective students

Any specific projects that are available will be advertised here. However, I am always looking for motivated students. So if you have an interest in evolutionary biology, behavioural ecology and (population or quantitative) genetics, and in particular in the interface between them, then don't hesitate to contact me to discuss the possibilities.


current projects

Individual-level causes and population-level consequences of variation in fitness

 Switzerland has only a very small number of wild and unmanipulated bird and mammal populations where individuals are marked individually and individual life-histories are being recorded. One of the few of such studies is that of a wild snow vole population (Chionomys nivalis), located in the Swiss Alps. This study population was established in 2006 by Dr. Peter Wandeler.
    Given its in many ways extreme environment, this population provides an excellent system to link life-history theory, quantitative genetics and population ecology to study the effects of environmental variation and climate change on the evolutionary dynamics of isolated populations. Furthermore, their relatively close relatedness to house mouse and rat ensures the availability of a range of genetic and genomic tools.


The evolutionary genetics of life and death in humans

 In this project, we take an evolutionary approach to variation in human reproductive success and lifespan, and try to understand how these are being shaped by genes and the environment. we do this by combining genealogical data with a range of other types of datasets. This can provide us with insights into how important life-history traits, like age at first reproduction, family size and lifespan, as well as a range of socio-economic variables, (co)vary among individuals, villages and regions, and how they have changed over time. By subsequently combining these data with ideas from population and quantitative genetics and life-history theory, we can make a first step towards elucidating the role of genes in shaping life and death, in the past and in the present.


Fitness meets fitness

 Evolutionary biologists are usually the first to emphasize that evolutionary fitness has little in common with the meaning that is commonly attached to fitness by the general public, that is physical fitness. Whereas biologists emphasize the role of performance in shaping evolutionary fitness in non-human animal populations, sports scientists aim at improving performance, i.e. physical fitness, of elite athletes in particular. However, both fields have more in common than generally believed.
    To show these parallels, I use concepts and methods from evolutionary biology, physiology and psychology to study the proximate and ultimate causes of variation in physical fitness, as well as in attractiveness, which is one aspect of evolutionary fitness. By combining physiological, morphometric and genetic data, I try to infer the past and present selective pressures acting on physical fitness in humans.


The genetic basis of inbreeding depression

 Inbreeding depression, the reduced survival and performance of individuals with related parents, is one of the oldest and longest standing topics in evolutionary genetics. The continued interest in inbreeding depression stems from the fact that it affects a large number of phenomena in biology, ranging from fundamental biological processes such as the choice of mating partner and the decision to leave one's birth place to conservation of endangered species, as well as human and animal health and productivity. Studies on inbreeding depression therefore contribute to both basic and applied research. However, despite a century of research on the genetic basis of inbreeding depression, the relative importance of various genetic causes is still debated.
     We aim to elucidate the genetic basis of inbreeding depression in natural populations. In particular, we use extensive field data on survival and reproduction of song sparrows (Melospiza melodia) on Mandarte Island and dipper (Cinclus cinclus) around Zurich, with modern molecular genetic approaches and recently developed statistical tools.


The giants of Aldabra

Aldabra tortoise In 2011, Dennis Hansen, Lindsay Turnbull, Gabriela Schaepman-Strub and myself initiated the Zurich-Aldabra Research Platform (ZARP) with money from the Forschungskredit of the University of Zurich. ZARP is a multi-disciplinary collaboration between scientists based mainly at the University of Zurich and the Seychelles Islands Foundation (SIF) that aims at supporting local SIF staff based on Aldabra Atoll in their research on the Aldabra giant tortoise. My main interest within this project lies with the population genetics of this population.


Previous projects

Y linkage of male ornamentation in guppies

 Male guppies are remarkable for their highly polymorphic colour patterns. Interestingly, there are several lines of evidence suggesting that at least part of the genetic variation underlying male coloration is linked to the Y chromosome. As a consequence, guppies provide a fascinating case study into the causes and consequences of sex-linked genetic variation. In this project, Rob Brooks and I used data from a multi-generation breeding experiment to estimate the amount of quantitative genetic variation underlying male ornamentation, both on and off the Y chromosome.
    Despite a growing awareness that organisms are not one-dimensional, the great majority of studies on the evolution of colour traits continues to reduce an animal's phenotype to a single measurement of one single trait. Evidence is however rapidly accumulating that this univariate approach provides us with an overly simplistic description of an individual's phenotype, and thereby it is unable to advance our understanding of the evolution of complex phenotypes like male ornamentation in guppies. For example, different traits, but also different aspects of the same trait, may provide different types of information, and correlations among them may severely limit there evolutionary trajectory.<


phd research

 In 2001 I started my PhD at the Department of Animal Population Biology at the Netherlands Institute of Ecology, to work on the evolutionary genetics of life-history traits in great tits (Parus major). During these four and a half years I gained ample experience with the estimation of quantitative genetic parameters and selection pressures from long-term data sets. I focussed on the population on the island of Vlieland in particular, where I also spent four field seasons.
    Vlieland is one of the smaller islands in the Dutch part of the Wadden Sea (53.17°N, 5.03°E, 3258 ha). The population consists of five more or less spatially separated woodlands (total surface ca 300 ha) and a small village. The landscape between the woodlands consists mainly of dunes and is unsuitable habitat for great tits.
    Since nest boxes are available in excess in all suitable nesting habitat, it is possible to monitor the complete population and to ring all chicks that are born on the island each year. As a result of the isolated nature of the population, immigration rates are relatively low, whereas local recruitment rates are high. This makes it possible to reconstruct individual pedigrees in great detail, and to obtain relatively accurate fitness measures for all individuals. These characteristics make Vlieland exceptionally suitable for a study into the evolutionary genetic of wild populations.

An electronic version my thesis can be found here