Abstract

We developed eight polymorphic microsatellites from the parasitic nematode Baylisascaris procyonis. Amplification of these loci in a sample of 74 worms collected from 10 raccoons in Western Michigan revealed significant population structure. Bayesian clustering indicates two subpopulations, one on either side of the Grand River which bisects the region sampled. Estimates of F_ST, and results from AMOVA and isolation by distance, further corroborate a scenario whereby the river is acting as a barrier to gene flow, a rather unusual finding given the high vagility of raccoons and microgeographic scale of the analysis. We describe one possible mechanism for how this pattern of structure could have become established.