Oliver Selz

Dr. Oliver Selz

Department Fish Ecology & Evolution

About Me

I have a broad interest in aquatic sciences, especially in the context of ecology, evolution and biodiversity of aquatic organisms’. My preferred approach to a research question is tackling it from multiple directions, employing different field, experimental and laboratory techniques in order to develop as much as possible an organic and coherent understanding of a system.

I have studied the ecology and evolution of different fish species. My main interest is understanding how ecological and evolutionary processes can shape biodiversity. The study systems that I use for understanding these processes are whitefish from different lakes in Switzerland and cichlid fish from the Great African Lakes.

I am currently a PostDoc on the project “whitefish diversity in Swiss lakes” hosted by EAWAG and in cooperation with the Federal Office for the Environment (FOEN). In this project we aim at assessing and describing the current state of whitefish (Coregonus sp.) species-diversity across most of the Lakes of Switzerland. The Alpine whitefish radiation constitutes a monophyletic group that has diverged in-situ into many species flocks and is native to around 40 lakes that are part of three major European drainage systems; the Rhine, Rhone, and Danube. In these post-glacial lakes (glacial retreat 12-20 kyr ago) intralacustrine diversity varies from one to six species and the species are phenotypically differentiated by traits related to feeding ecology (e.g. gill raker number) and traits linked to reproductive isolation (e.g. time and depth of spawning). The major goal of this project is to generate a comprehensive database on the ecology, behaviour, morphology, genetics and evolution of whitefish in Switzerland, by combining existing data on the different species with data that we collect in the field and lab. As part of this we will systematically describe yet taxonomically un-described, but known whitefish species and create a identification key. Currently 28 different species of whitefish are known, of which 10 are not yet formally described taxonomically. This compendium of information on whitefish diversity will enable lake and fisheries managers, environmental offices, sports and commercial fisherman and the interested public to identify, monitor, manage and protect this amazing endemic fish diversity found in Switzerland, the so-called water tower of Europe.

In my PhD I have studied how hybridization between African cichlid fishes can influence speciation and adaptive radiation. Hybridisation between species is a pervasive phenomenon in nature that occurs naturally, but is often also linked to anthropogenic pressures that change the state of a system. The different studies of my PhD showed that the effect that hybridization has on evolutionary processes and speciation is manifold: it can act both as a hindering or stimulating force and depends strongly on the ecological context.

In a similar vein in my master thesis I studied how anthropogenically induced eutrophication of Lake Victoria may influence the propensity for cichlid species to hybridise. I was able to show in lab-experiments that eutrophication-induced turbidity hampers visual communication between two cichlid species (Pundamilia pundamilia and P. nyererei) which is essential for assortative mating, and thereby increases the chance of hybridisation. This work helped to understand the fate of species in changing environments and highlighted the importance of measures to counteract the on-going eutrophication of Lake Victoria.

In my bachelor thesis I studied the adaptive radiation of white fish from Switzerland. The number of phenotypically distinct sympatric species within each lake vary (1 to 5 species). I was able to show that phenotypic diversity can also be predicted by ecological determinants via stable isotope analysis.

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We work to combat what we consider the largest stumbling block on the way to successful biodiversity management and conservation in aquatic ecosystems: the lack of quantitative baseline data
We investigate the mechanisms of speciation and adaptive radiation

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Curriculum Vitae

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Phone: +41 58 765 2146
Fax: +41 58 765 2168
Address: Eawag
Seestrasse 79
6047 Kastanienbaum
Office: SL B19

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Research Focus



Adaptive Radiation




Behavioural Ecology


Adaptive Radiation




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