Research Focus
Why Sex?
This simple question is a
major conundrum in evolutionary biology.
The central question is as follows: what selective forces maintain sexual reproduction and genetic recombination in nature?
John Maynard Smith, in The Evolution of Sex 1978
Sex has many costs. Demographic costs of males, transmission costs, costs of mating (predator exposure and STDs), and so on. But why are then the huge majority of organisms mixing genomes through sexual reproduction involving males and females, when there is the straight-forward way of just producing asexual (parthenogenetic) females? What are the profound advantages of sex that offset its costs in most organisms?

One way to find out what the big benefits of costly sex are, is to compare sexuals with their asexuals relatives to identify the differences. In that way theoretical predictions can be empirically tested. Nowadays this happens via the generation and analyses of (population) genomic data.
Ancient Asexual Scandals
In our lab, we focus on animals that persisted in the absence of sex for millions of years. Normally, asexual lineages are thought to be driven to extinction because of ineffective selection. However, many species of asexual oribatid mites are able to adapt, diversify and get rid of harmful mutations. They are evolutionary scandals, because they escape their fate of extinction.

Such incidences of ancient asexuals are important to study, because identifying the singularities that allow for their evolutionary persistence through time will help vice versa to identify the benefits of sex.

“All you really need to know for the moment is that the universe is a lot more complicated than you might think, even if you start from a position of thinking it’s pretty damn complicated in the first place." — Douglas Noel Adams

Projects we are working on right now
Meselson effect

In asexual mites, do intra-individual haplotypes diverge over time (Meselson effect)?
-> It seems so!

How do asexuals speciate? What are genomic features of speciation? Do asexual species occupy ecologically different niches and are these signatures found in genomes?
Escape extinction

How can asexual mites maintain effective selection? Because of large and stable populations and/or effective repair mechanisms?
Asexual Innovation

Is plasticity a feature of asexual genomes? Are they more free to evolve novelty? How do sexual and asexual genomes differ?
Single individuals

We use new sequencing technologies for generating chromosome scale genomes from very little DNA amount of single individuals
Sex determination

How do mites produce males and females? Are there sex chromosomes?
MSc and BSc theses

We are open for own project ideas.

We communicate our results with the public and try to spark the excitement for science in kids.
Meet our team
This is the core research team.
Jens Bast
Principal Investigator
Jens takes care of the big picture. He develops the direction of research, takes care of scientific needs of group members and the labs funding.
Hüsna Öztoprak
PhD student and Lab lead
Hüsna is interested in the evolution of asexual speciation. She develops new methods for processing small animals in the wet-lab for genomics. These allow her to link ecology, morphology and genomics in her work.
Shan Gao
PhD student and Bioinfo lead
高山 is interested in the bioinformatic side of things. He analyzes the genomic landscapes of asexuals and sexual relatives and identifies what makes them special.
Nadège Guiglielmoni
Postdoctoral researcher
Nadège is interested in assembling tricky animal genomes to chromosome and haplotype level using long reads and Hi-C, and she develops tools for assembly. She works in the Sex Lab and in the Worm Lab in a joint research effort about consequences of asexuality.
Svenja Wulsch
Master student
Svenja is interesed in sex determination of the non-model organism Hermannia gibba.
Yichen Zheng
Postdoctoral researcher
Yichen is interested in the population dynamics of old asexuals using simulations and empirical data
Our publications (selection)
Short description of selected published papers
The Meselson effect in mites
Haplotype divergence supports long-term asexuality in the oribatid mite Oppiella nova.
Brandt et al. 2021 PNAS
What are common features of asexual genomes?
Genomic Features of Parthenogenetic Animals
Jaron et al. 2021 J Hered
TEs are benign in asexuals
Asexual reproduction reduces transposable element load in experimental yeast populations
Bast et al. 2019 eLIFE

Selection works better for asexual mites than sexuals
Effective purifying selection in ancient asexual oribatid mites
Brandt et al. 2017 Nat Commun

Mutation accumulation and arrested gBGC in asexual Timema
Consequences of Asexuality in Natural Populations: Insights from Stick Insects
Bast et al. 2018 MBE
TEs load in nature is not influenced by reproductive mode
No Accumulation of Transposable Elements in Asexual Arthropods
Bast et al. 2015 MBE

If you want to discuss science with us, you can find us here.
Institute for Zoology, University of Cologne
Zülpicher Str 47b, 50674 Köln
Phone: +49 221 470 3119
E-mail: jbast [at]

We are located in the Biocenter.
The nearest trainstation is Köln Süd
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