Evolutionary Biology
Schärer Group
Group Members
Main Questions
Current Research
Former Research
Research Methods

Schärer Group
Evolutionary Biology
Zoological Institute
University of Basel
Vesalgasse 1
CH-4051 Basel

Nikolas Vellnow

email: nikolas.vellnow@unibas.ch
phone: +41 61 207 03 75
fax: +41 61 207 03 62

I am a Ph.D. student in the research group of Lukas Schärer and I am interested in sexual selection and cytonuclear conflict in simultaneous hermaphrodites.

Current research

I started my PhD in January 2013 and I have worked on the following questions using the simultaneously hermaphroditic Macrostomum lignano, the model species in our lab:

1) Estimating whether different cytotypes explain phenotypic variance in sex allocation, as predicted under cytonuclear conflict over sex allocation, using a quantitative genetic breeding study.

2) Testing if and under what conditions variation in testis size translates into paternity success.

3) Testing for genotype effects of the sperm donor, the sperm recipient and their interaction on outcomes of different episodes of postcopulatory sexual selection.

For my experiments I made use of the extremely valuable methods previously developed by the Schärer Group. The availability of fluorescent green worms for example makes determining paternity success extremely easy and cheap and since the sperm also express the green flurescent protein.

Former research

During my Masters, I worked with Physa acuta, a simultaneous hermaphroditic freshwater snail studying if the level of mating competition affected inbreeding depression and the opportunity for sexual selection. And indeed I showed that the male sex function of individuals under strong mating competition suffered stronger inbreeding depression and experienced a stronger opportunity for selection. This effect was particularly strong during the postcopulatory stage when individuals had to compete with previously installed sperm from a competitor. Those results confirm the view that postcopulatory sexual selection is an important factor in simultaneous hermaphrodites. During this research I was supervised by Patrice David and Tim Janicke at the CEFE in Montpellier.

I also did a theoretical project about the maintenance of sexually antagonistic genetic variation under polygenic inheritance with Göran Arnqvist at the Uppsala University and Franjo Weissing at the University of Groningen. I used an individual-based simulation approach to explain the ample empirical evidence for sexually antagonistic genetic variation in nature. I found that expanding the number of fitness determining loci from the one or two loci in previously published population genetic models did not change their conclusions significantly. Whether one or many loci determine fitness, the most important parameter for explaining sexually antagonistic genetic variation is the sex-specific dominance of the alleles involved.

Curriculum vitae

Born in 1987 in Neuss, Germany.

2013 to present

Ph.D. in Evolutionary Biology, University of Basel.


M.Sc. in Evolutionary Biology, University of Groningen and University of Montpellier 2 (Erasmus Mundus Master in Evolutionary Biology: MEME).


B.Sc. in Biology, Bielefeld University.


Vellnow, N., Vizoso D.B., Viktorin G., Schärer L. (under review), No evidence for strong cytonuclear conflict over sex allocation in a simultaneously hermaphroditic flatworm.

Arnqvist, G., Vellnow, N., Locke, R. (2014), The effect of epistasis on sexually antagonistic genetic variation. Proc. R. Soc. B. 281: 20140489.

Janicke, T., Vellnow, N., Lamy, T., Chapuis, E., David, P. (2014), Inbreeding depression of mating behavior and its reproductive consequences in a freshwater snail. Behav. Ecol. 25: 288-299.

Janicke, T., Vellnow, N., Sarda, V. and David, P. (2013), Sex- specific inbreeding depression depends on the strength of male-male competition. Evolution. 67: 2861-2875

this page was last updated on Wednesday, December 14, 2016