This Thursday, Dr. Scott Colbourne will talk on
Sympatric speciation: Foraging ecology and sexual selection in pumpkinseed sunfish (Lepomis gibbosus)
at 12:30 in the EEB lounge (BioSciences 4338)
The seminar is hosted by Fran Bonier
Sympatric speciation is typically thought to require both disruptive natural selection and a mechanism of reproductive isolation that results in genetic differentiation. Divergent selection related to foraging has been described in many taxa, but the contribution of foraging to reproductive isolation and ultimately sympatric speciation are not yet well understood. Here I used stable isotope analysis of diet and morphological analysis of body shape to examine phenotypic divergence between littoral and pelagic foraging ecomorphs in a population of pumpkinseed sunfish (Lepomis gibbosus). I then examined reproductive isolation between ecomorphs by comparing the isotopic compositions of nesting males to eggs from their nests (a proxy for maternal diet), and used nine microsatellite loci to examine genetic divergence between ecomorphs. The data support the presence of distinct foraging ecomorphs in this population and indicated that there is significant positive assortative mating based on diet. However, there was no evidence of genetic divergence between ecomorphs, indicating that isolation is either relatively recent or is not strong enough to result in genetic divergence. Based on our findings, pumpkinseed sunfish represent an interesting system in which to further explore the mechanisms by which natural and sexual selection contribute to phenotypic and genetic divergence within a population, prior to the occurrence of sympatric speciation.
Scott is currently a post-doctoral fellow at the Great Lakes Institute for Environmental Research in Windsor, ON working with Aaron Fisk and Dan Heath on the foraging ecology of Great Lakes fishes and the development of eDNA detection techniques for invasive species. In this seminar he will be focused on his PhD research with Bryan Neff and Fred Longstaffe at the University of Western Ontario during which he focused on the foraging ecology of sunfish in relation to reproductive tactics, sexual selection, invasive species, and sympatric speciation.