Welcome to the American Ornithological Society 2018 Annual Conference. We are pleased to have you join us at the lovely Hilton El Conquistador Resort in Tucson, AZ.
The Northwestern Crow (Corvus caurinus) has long been a controversial taxon because it is morphologically and behaviorally indistinguishable from the American Crow (Corvus brachyrhynchos) near the poorly defined range boundary in northwestern Washington state. Using recent museum specimens from across the ranges of both taxa, we found two clades of mitochondrial DNA haplotypes that likely diverged during the Pleistocene, consistent with past isolation in glacial refugia. The geographic distribution of these clades approximates the published ranges of Northwestern and American, and an overlap zone in northwestern Washington and western British Columbia where crow populations contain both haplotype groups is consistent with secondary contact. Using ddRAD SNPs from the nuclear genome, we inferred a phylogeographic pattern consistent with the mitochondrial signal and discovered that all crows in a broad area of western Washington and southwestern British Columbia are hybrids. Thus, these two taxa are conspecific under the biological species concept. Interestingly, the hybrid zone coincides with the most heavily urbanized part of the Pacific Northwest. One published hypothesis is that human land use changes and urbanization since {raise.17exhbox{\$scriptstylemathtt{sim}\$}}1850 have allowed crow populations to expand into new anthropogenic habitat types, reducing assortative mating and increasing the geographic breadth of the overlap zone. We use DNA sequences from 19th century museum specimens to test the hypothesis that the geographic distribution of Northwestern and American Crows has changed during the past 100 to 150 years.
