Justyna Wolinska
Ph.D. (2006)Eawag Switzerland

go to my new page (LMU Munich)

My research focus is on the ecology and evolution of host-parasite interactions. Specifically, A) I have been investigating the role of parasites (and predators) in maintaining the coexistence of species in Daphnia (water fleas) hybridizing systems (PhD project, Switzerland, Eawag/ETH) and currently B) I am involved in the project headed by Mike Lynch that investigates the most striking question in evolution: “why sex and recombination?” (Postdoc project, Indiana University, Department of Biology).

A) The role of parasites in hybridizing host communities

Hybridizing systems are very attractive because in contrast to slow evolutionary processes like drift or mutations, hybridization might change genetic diversity within one generation. In particular, I am looking for evidence of parasite-driven frequency dependent selection in natural populations of Daphnia hybridizing systems. The dynamic coevolutionary aspect of host-parasite interactions is often neglected in hybridizing hosts; differences in infection levels between parental species and hybrids are considered to be fixed. My project challenged this idea; indeed, I found that species that are rare and under-infected are likely to increase in frequency and subsequently to become over-infected. I additionally confirmed some assumptions of a model of negative frequency-dependent selection under experimental conditions. In contrast to common knowledge about hybridizing systems, I believe that the infection patterns as observed under natural conditions may be rather temporal and unstable.

parasites infecting Daphnia galeata x hyalina x cucullata species complex

bacterium yellowish bacterium whitish Saprolegnia sp. Caullerya mesnili

B) Why sex and recombination?

Our model system is Daphnia pulex, which consist of both sexual and asexual races. Together with Curt Lively I am investigating the potential role of parasites in maintaining the unusual coexistence of these reproductive systems. At the moment I am in the process of developing a new host-parasite system (Daphnia pulex - water mould parasites) which may eventually  be a very powerful tool, because water mould parasites are highly virulent and thus can impose tremendous selective force their hosts. Moreover, in contrast to Daphnia parasites used in other laboratories, water moulds can be cultured in vitro.

parasites infecting Daphnia pulex

Saprolegnia sp. Saprolegnia sp. on agar Aphanomyces sp. Aphanomyces sp. on agar