Research Interests

I am interested in evolutionary mechanisms that shape reproductive systems in animals. The “general rule” of animals having two sexes which equally contribute to the nuclear genome of individuals in the next generation is not as general as it might seem. Reproduction in animals is very diverse, including systems with asexual reproduction in all-female species, bi-sexual species in which the genome is clonally transmitted by only one of the two sexes, and systems with more than two sexes. Different modes of reproduction may have very different consequences at the genetic, population and community levels and strongly influence the evolutionary trajectory of a species.

In my current projects in Bernie Crespi’s Lab, I use Timema stick insects to identify evolutionary mechanisms leading to the loss of sexuality. Timema is a small genus which comprises about 22 wingless, plant-feeding species, five of which reproduce asexually. The five asexual species represent independent transitions from sexuality to asexuality and each asexual has an ecologically similar sexual sister species. These characteristics make the genus an ideal model system for analyzing the evolution of sex and asexuality, identifying selective asymmetries between sexual and asexual lineages and the genetic basis underlying parthenogenesis. By combining population genetics tools with breeding experiments and cytogenetic analyses, we try to understand how asexual reproduction in Timema stick insects functions, how it has evolved, and how it is maintained.

My previous research focused on Pogonomyrmex harvester ant lineages, which obligately co-occur as complementary pairs because workers develop from inter-lineage crosses while new queens develop from same-lineage crosses. This system can be viewed as a transition to more than two sexes (see Parker, 2004) because females of each lineage need to mate with males of two different lineages, one to produce workers (which are comparable to the soma of non-social animals) and the second lineage to produce new queens (comparable to the germline in non-social animals). These lineages have probably evolved after complex hybridisation events which created genetic incompatibilities in the worker developmental pathway. Research in this system is done in collaboration with Sara Helms Cahan (University of Vermont) and Laurent Keller (University of Lausanne).