Electronic Thesis and Dissertation Repository


Master of Science




Dr. Beth MacDougall-Shackleton


Although much speciation occurs in allopatry, populations with overlapping geographic ranges may also experience reduced gene flow due to ecological differences. Parasites are an important feature of the biotic environment, and place important selective pressures on their hosts, potentially reducing gene flow among geographically separated host populations. However, virtually nothing is known about host-parasite interactions in systems where hosts have nomadic distributions, and where ecologically distinct populations exist in sympatry. I examined population genetic structuring and characterized bloodborne parasite communities across four ecologically distinct, but partially sympatric, “vocal types” of nomadic red crossbills (Loxia curvirostra) sampled at multiple sites. I found evidence for isolation by distance in one vocal type, but vocal types were not genetically differentiated from one another, nor were they characterized by significantly different parasite communities. Despite differences in foraging ecology, crossbill vocal types do not appear to be incipient species or subject to different parasite communities.