Rangewide and local barriers to gene flow in white-crowned sparrows (Zonotrichia leucophrys)

Abstract

Although white-crowned sparrows (Z. leucophrys) have been extensively researched for physiology and behaviour, surprisingly little recent work has been done to characterize the population genetic structure of this widespread North American passerine. This study used molecular markers and habitat modelling to test theories of Pleistocene refugia that could explain current subspecies delineations, then investigated rangewide and local barriers causing contemporary genetic differentiation across the geographical range of three subspecies: Z. l. gambelii, Z. l. oriantha, and Z. l. pugetensis. Phylogenetic analysis showed weak and inconclusive support for the genetic differentiation of subspecies and the theories of their Pleistocene origin. Mitochondrial, nuclear Z-linked, and microsatellite markers show a north-south genetic split caused by isolation by distance, and an east-west split caused by mountains as a barrier to gene flow between Alberta and British Columbia populations. Analysis revealed the importance of habitat ecotype and anthropogenic disturbance on contemporary population genetic structure.