Forschungsschwerpunkte

Density influences selection; selection influences genetic make-up; and in turn, genetic make-up influences density.
D. Pimental, 1961, The American Naturalist, 95

We are interested in how communities respond to changes in genetic diversity, rapid evolution, changes in intrinsic and extrinsic parameters, and food web structure. We seek to link genetic and phenotypic variation to population dynamics, to understand the ecological consequences of evolutionary processes and the evolutionary consequences of ecological interactions (eco-evolutionary feedback dynamics).

Therefore we study how ecologically important traits evolve under different ecological conditions and how phenotypic changes are determined at the genetic level and how genetic diversity is maintained. To gain insight into these fundamental processes, we  use empirical data derived from experiments using fast-growing organisms (e.g., rotifers, green algae and aquatic viruses).

Eco-Evolutionary Dynamics

 

Rapid evolution has recently been recognized as an important player for many ecological processes. It is now well recognized that evolutionary change can affect the interactions between species within a few generations and that ecological interaction can influence the outcome of evolution in return. However, the concept of these so-called eco-evolutionary dynamics has not been fully integrated into our current thinking on how we for instance manage populations and biodiversity.

In our lab we use microcosm experiments in combination with mathematical modeling and sequencing to study eco-evolutionary feedback dynamics for different species interactions and communities. Fast growing, aquatic organisms (e.g., the rotifer Brachionus calyciflorus and the green alga Chlamydomonas reinhardtii) enable us to follow evolutionary change and ecological dynamics at the same time for dozens of generations.  We link ecological and evolutionary change to dynamics on the genome and transcriptome level to improve our understanding of evolutionary changes on the molecular level and the mechanisms that underlie adaptive evolutionary responses on the time-scale of the ecological and environmental changes that evoke rapid evolutionary responses.

Why sex?

 

Explaining the prevalence of sexual reproduction over asexual reproduction across animals and plants is an ongoing challenge in biology. While numerous mechanisms have been hypothesized to explain the evolution of sex, there is still no conclusive understanding of the conditions under which sex is beneficial. Because sexual reproduction comes with several disadvantages – the so-called costs of sex – the predicted conditions for sex to be advantageous are often limited.

Despite extensive study, there is little empirical support for any of these theories. Indeed, tests of theory through experimental evolution of sex have been almost absent. Using facultative sexual rotifers of the genus Brachionus and/or the green alga Chlamydomonas reinhardtii we test and develop hypothesis on the evolution of sexual reproduction. We use these systems to go one step further and study the underlying population genetic mechanisms and link them to the large body of theory.

Aquatic Viruses

 

Aquatic viruses infecting bacteria or algal species are considered to be key players in structuring microbial communities and biogeochemical cycles due to their abundance and diversity within aquatic systems. Their high reproduction rates and short generation times can make them extremely successful, often with immediate and strong effects for their hosts and thus in biological and abiotic environments. There is, however, very little known about the relative role of aquatic viruses in lake systems. To better understand the ecology and evolution of aquatic viruses, we study viruses infecting algal cells by combining lake sampling and laboratory experiments and develop high-throughput methods for measuring their traits and how the traits change over time, e.g., over the course of an experiment or a season. We are specifically interested in how traits involved in the interaction with the host and other viruses change.