| Using a combination of mitochondrial and z-linked sequence data, microsatellites and spatio-geographical modelling, I examine the historical and contemporary factors influencing the genetic structure of the purple finch (Carpodacus purpureus). The last glacial maximum likely forced the purple finch into multiple refugia: one on the Pacific Coast, one in south western United States, and one off the Atlantic shelf. The two subspecies remain distinct lineages, with little evidence of gene flow between C. p. purpureus and C. p. californicus. The contact zone between subspecies appears in south western British Columbia. As C. p. purpureus expanded from their refugia following a stepping-stone model, eastern and western populations came into secondary contact, resulting in extensive admixture. Contemporary levels of gene flow between populations are low with at least five genetic clusters, likely due to high site fidelity and morphological variation upon which mate selection occurs. Physical barriers do not appear to affect dispersal of the purple finch. |
