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This is a project I started working on as a post-doc at the Evolutionary Botany Department at the University of Neuchatel, Switzerland. During this time I analyzed data comparing geographic variation in neutral ganetic markers and in traits potentially involved in complex plant-insect interaction on the dioecious plant Silene latifolia and its pollinator-seed predator Hadena bicruris. This was quite a new experience for me as it was the first time I worked on species interactions involving organisms from different kingdoms, and looked at questions related to mutualism and coevolution. It was interesting to apply techniques that I had used to study fish to a completely novel system.
As a first part of the project I analyzed the spatial scale of genetic structure within and among nine populations of the white campion, Silene latifolia and its main pollinator and seed predator Hadena bicruris along a latitudinal gradient across northern/central Europe. Silene latifolia is a dioecious, short lived plant that inhabits patchy, often disturbed environments. It is pollinated primarily by the moth Hadena bicruris, who is also a specialist seed predator that reproduces by laying eggs in S. latifolia flowers. The larvae of H. bicruris feed on the seeds of S. latifolia. The analyses of neutral genetic markers revelead significant genetic structure among populations of S. latifolia but not for its pollinator / seed predator, suggesting that despite migration among populations of H. bicruris, pollen is not, or only rarely, carried over between populations, thus maintaining genetic structure among plant populations. This indicates that while significant structure of S. latifolia populations creates the potential for differentiation at traits relevant for the interaction with the pollinator / seed predator, substantial gene flow in H. bicruris may counteract this process in at least some populations.
The analyses of the geographic variation of phenotypic traits relevant for the interaction with the pollinator / seed predator is published in Evolutionary Ecology. We compared divergence in both plant and moth traits across the same 9 populations and compared patterns of phenotypic variation with those of neutral genetic variation. We found that populations of both plant and moth are significantly different for several traits, but these differences are not correlated with genetic differences. The most important differences were actually between sexes of the plant species, males tend to be smaller than females. We found no differences between sexes in the pollinator.
I hope that this comparative analyses of spatial genetic and phenotypic structure of populations of plants and the insects they interact with will help us understand better how gene flow, natural selection, and genetic drift may jointly influence the distribution of genetic and phenotypic variation and potential for local co-adaptation for interacting species.
Collaborators: Giorgina Bernasconi (supervisor), Anne Marie Labouche, Gabriela Gleiser
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