Tanja Schwander

I am interested in the origin and the evolutionary consequences of genetic caste determination in hybridising lineages of Pogonomyrmex harvester ants.

Workers in most social insects are at least partly sterile and thus they reproduce indirectly by favouring the reproduction of the queen. Genetic similarity of reproductive and worker individuals within a colony is presumed to be a fundamental prerequisite for the evolution and maintenance of this reproductive division of labour. However, this view has been challenged by the discovery of consistent genetic differences between the queen and worker castes in hybridising lineages of harvester ants in the genus Pogonomyrmex. Queens of these lineages mate with males of both lineages, but surprisingly, young virgin queens are nearly always fathered by same-lineage males, while workers are invariably interlineage hybrids. Non-hybrid individuals have even lost the potential to develop into workers and in consequence, the queens that are not mated to males of the other lineage fail in founding new colonies. Despite this apparent mutual dependence and the frequent interlineage mating, all lineages described so far are completely isolated gene pools.
In my PhD I will try to get some insight into how these lineages interact and what kind of factors contribute to the apparent isolation of the populations. We use population genetics tools to describe the organisation of sympatric populations and to distinguish independent origins of the caste determination system.

Born on July 3, 1978 in Brugg, Switzerland

2003 -
PhD under the supervision of Dr. Sara Helms Cahan and Prof. Laurent Keller

2003
Diploma thesis under the supervision of PD Dr. Michel Chapuisat: Division of labour and worker size polymorphism in ant colonies: the impact of social and genetic factors

1998 - 2003
Studies in Biology at the University of Lausanne, Switzerland