Patterns of genetic differentiation in orange-crowned warbler Vermivora celata populations across their breeding range

The orange-crowned warbler Vermivora celata is a Neotropical migrant passerine broadly distributed across North America. The breeding range of this species would have been subject to a cycle of contractions and expansions during Pleistocene glaciations. This may have isolated populations in different glacial refugia resulting in allopatric differentiation. This scenario has been invoked to explain concordant biogeographic patterns seen in many North American taxa. The orange-crowned warbler breeds on Haida Gwaii, British Columbia (formerly know as the Queen Charlotte Islands). Largely due to a pattern of morphological endemism in diverse taxa, a glacial refugium is thought to have persisted in the area of this archipelago during late Pleistocene glaciations.; To investigate intraspecific genetic structure in the orange-crowned warbler on continental and regional scales, I analysed patterns of microsatellite variability among seven breeding localities encompassing two of the four described subspecies. I found low genetic differentiation among populations ( FST = 0.022), with significant continental-scale structuring and weak differentiation within western populations. I did not find evidence of a genetically endemic population of orange-crowned warblers in Haida Gwaii. Microsatellite differentiation supports the classification of two of the four currently recognized subspecies (V. c. celata and V. c. lutescens). Evidence of equilibrium between gene flow and drift supports a hypothesis of restricted contemporary gene flow between V. c. lutescens and V. c. celata. Further genetic research, including analysis of V. c. orestera and V. c. sordida, is required to fully elucidate the taxonomy and conservation priorities of this species.