Master projects at the Zoological Institute

Below is a short outline of some of the areas in which groups in the Zoological Institute offer master projects. Further topics can be discussed with the group leaders. The projects are deliberately vague, as the details shall be worked out with the candidates. The development of the details of a project is an important part of doing a master thesis.

Interested candidates should contact the group leaders directly.

Group: Walter Salzburger

Ecological speciation in East African cichlid fishes

The adaptive radiations of cichlid fishes in the East African Great Lakes represent the most species-rich and diverse animal adaptive radiations. More than 1500 cichlid species have evolved in lakes Tanganyika, Malawi and Victoria in a period of no more than a few million years only. The evolutionary success of the cichlids can be attributed to several ecologically relevant and, hence, naturally selected traits such as mouth morphology, but also to sexually selected traits such as coloration (see Salzburger 2009; Molecular Ecology). This project aims to test whether ecological speciation is the causal factor of diversification in cichlids from Lake Tanganyika. To this end, closely related species pairs will be compared in terms of their ecological adaptations.

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The adaptive radiation of the Tropheini from Lake Tanganyika

Lake Tanganyika is the oldest of the three East African Great Lakes and harbors the morphologically, ecologically and genetically most diverse assemblage of cichlid fishes. Unlike in lakes Victoria and Malawi, where only one group of cichlids (the haplochromines) have radiated, the Tanganyikan cichlid assemblage consists of several parallel adaptive radiations. One of these are the Tropheini, a group of about 30 mostly rock-dwelling species. The aim of this project is to study the adaptive radiation of the Tropheini by integrating phylogenetic and population genetic analyses with eco-morphological assessments of all species belonging to this group.

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Group: Dieter Ebert

The ecology and evolution of host-parasite interactions in natural populations

Parasites and pathogens are the largest functional group of species on earth. In natural ecosystems, the vast majority of organisms suffer from some forms of infection. This goes hand in hand with reduced fecundity and survival, lower chances of mating and even with the extinction of local populations. Surprisingly, we still know only very little about the impact of infectious diseases on the ecology and evolution of their hosts. In a long term field project in Southern Finland, we study the impact of infectious diseases on host species of the genus Daphnia. Populations of Daphnia occur in small rock pools on the Skerry islands in the Baltic Sea. In our project we combine experimental work in the field with observations from natural populations. Within our Finland-project several options for master projects are open. The details of project will be worked out with potential master students, to fit the individual interests of the candidates.

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Field station in Finland:

Understanding coevolution: A detailed analysis of coevolution in Daphnia and two of its microparasites

Evolution does not take place in isolation, but rather within a framework of interacting species. Darwin called this "the tangled bank of nature". While coevolution of complex communities is difficult to understand, science made good progress in understanding how pairs of antagonists coevolve. However, we still lack good examples of well documented cases of specific antagonistic coevolution. Host - parasite interactions are often cited as prime examples for this form of coevolution, but evidence is rather thin. Using field and laboratory research we try to understand the coevolution between Daphnia magna and two of its main parasites, the bacterium Pasteuria ramosa and the microsporidium Octosporea bayeri. Within this larger project a number of questions are well suited for master project. The details of project will be worked out with potential master students, to fit the individual interests of the candidates.

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Group: Lukas Schärer

Mechanisms of sexual selection and the evolution of sex allocation

Simultaneous hermaphrodites are male and female at the same time. Individuals therefore need to decide how to distribute limited reproductive resources to their male and female function (e.g. to the production of sperm or eggs). This decision is called sex allocation, and it is an important life history decision in all sexually reproducing organisms. In our earlier work we have shown that the free-living flatworm Macrostomum lignano is a highly suitable model organism to study this question. In this project we will study how different mechanisms of sexual selection, such as sperm competition and cryptic female choice, are important determinants of the evolution of sex allocation, and how these interact with the mating behaviour. The details of project will be worked out with potential master students, to fit the individual interests of the candidates.

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Sexual conflict and the evolution of sperm and genital morphology

In simultaneous hermaphrodites we can expect that individuals often have identical, and therefore incompatible, mating interests (e.g. both individuals may want to give, but not receive sperm). This can lead to a serious conflict of interest over how matings should occur and what should happen to the sperm an individual has received from a partner. These sexual conflicts lead to rapid evolution of sperm and genital morphology. In this project we will study these questions in members the free-living flatworm genus Macrostomum, combining a comparative approach, and experimental work in selected species. The details of project will be worked out with potential master students, to fit the individual interests of the candidates.

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Group: Valentin Amrhein

Communication and sexual selection in songbirds

The song of male birds serves to attract females and to repel males. In studies on nightingales and on winter wrens, we aim to identify strategies that males pursue to accomplish these goals. For example, birds often sing in communication networks in which third individuals can obtain information on the quality and motivation of two males by listening to their singing interactions. We use song playbacks to simulate such interactions between males, to investigate the effect on the interacting birds themselves, or on other birds that listen to the interactions such as male neighbours or mate-searching females. To study how males choose their territories and how females choose their mates, we also use radio-telemetry.

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Songbird migration and winter ecology

Every year, about 2 billion songbirds migrate from Europe to sub- Saharan Africa. Long-distance migrants such as the nightingale have to cope with highly variable environmental conditions in different ecosystems across large geographical scales. To understand the ecology of a species and to take effective conservation measures, we need to know the migration routes of the birds. However, virtually nothing is known about the location of wintering grounds and about habitat use in sub-Saharan Africa in any European songbird. In collaboration with the Swiss Ornithological Institute (Schweizerische Vogelwarte Sempach), we study year-round movements, migration, and winter ecology of nightingales from breeding sites in England, France, Italy and Bulgaria.

see and (link "Mitarbeit") for further information.

Group: Daniel Berner

The genomics of diversification in threespine stickleback fish

Understanding adaptive divergence and speciation benefits from knowledge about the selective environments promoting phenotypic diversification on the one hand, and the genomic changes encoding this diversification on the other hand. While studying the former has been a traditional goal in evolutionary biology, we still have a vague idea about the genomic basis of adaptation. How many genes are under selection when populations start diverging? Are the same genetic variants recycled when multiple populations adapt to similar habitats? What molecular signatures emerge around genes targeted by selection? To shed light on such questions, my group makes use of a top empirical system for evolutionary genetic research – threespine stickleback fish. In particular, we focus on stickleback from Lake Constance (Switzerland, Austria, Germany), and on derived populations that have very recently colonized multiple inlet streams of Lake Constance. These lake and stream populations have different life styles and experience divergent natural selection, allowing powerful genomic investigation grounded in a solid ecological framework. Several PhD and master projects are currently running, but opportunities for new projects.exist – I am happy to develop these with interested students.

Threespine stickleback occurring in the Lake Constance basin exhibit dramatic divergence in elements of their life cycle (so-called life history traits). For example, individuals from the lake are large-bodied and can live up to three years, whereas individuals from inlet streams of Lake Constance are only half as large and generally die after reproducing at one year of age. This life history divergence is important to understanding reproductive isolation between lake and stream populations (and hence the initiation of species formation), because body size is often used as a cue for mate choice in stickleback. Nevertheless, we currently do not know to which extent this divergence is genetically based (local adaptation to lake and streams), or induced directly by the environments (phenotypic plasticity). We are trying to resolve this question through a combination of field and laboratory experiments. Further experiments suited for a master project could be discussed.

See here for further information.