Abstract
Accurate knowledge of geographic ranges and genetic relationships among populations is important when managing a species or population of conservation concern. Along the western coast of Canada, a subspecies of the northern goshawk (Accipiter gentilis laingi) is legally designated as Threatened. The range and distinctness of this form, in comparison with the broadly distributed North American subspecies (Accipiter gentilis atricapillus), is unclear. Given this morphological uncertainty, we analyzed genomic relationships in thousands of single nucleotide polymorphisms identified using genotyping‐by‐sequencing of high‐quality genetic samples. Results revealed a genetically distinct population of northern goshawks on the archipelago of Haida Gwaii and subtle structuring among other North American sampling regions. We then developed genotyping assays for ten loci that are highly differentiated between the two main genetic clusters, allowing inclusion of hundreds of low‐quality samples and confirming that the distinct genetic cluster is restricted to Haida Gwaii. As the laingi form was originally described as being based on Haida Gwaii (where the type specimen is from), further morphological analysis may result in this name being restricted to the Haida Gwaii genetic cluster. Regardless of taxonomic treatment, the distinct Haida Gwaii genetic cluster along with the small and declining population size of the Haida Gwaii population suggests a high risk of extinction of an ecologically and genetically distinct form of northern goshawk. Outside of Haida Gwaii, sampling regions along the coast of BC and southeast Alaska (often considered regions inhabited by laingi) show some subtle differentiation from other North American regions. These results will increase the effectiveness of conservation management of northern goshawks in northwestern North America. More broadly, other conservation‐related studies of genetic variation may benefit from the two‐step approach we employed that first surveys genomic variation using high‐quality samples and then genotypes low‐quality samples at particularly informative loci.
Highlights
Conservation policy and management are becoming increasingly important for the survival of wildlife populations, given the growing impact of human populations on the environment (Barnosky et al, 2011; Côté, Darling, & Brown, 2016; Robinson, 2006)
Given that many of the northern goshawk samples are from shed feathers or museum skin samples that provided DNA of insufficient quality for the GBS analysis, we developed assays for 10 markers with high frequency difference between the two main genetic clusters revealed by our genome‐wide analysis
Analysis of the North American northern goshawk samples clearly reveals two genetic clusters: one that includes all individuals from Haida Gwaii (HG) and a second containing all remaining North American individuals
Summary
Conservation policy and management are becoming increasingly important for the survival of wildlife populations, given the growing impact of human populations on the environment (Barnosky et al, 2011; Côté, Darling, & Brown, 2016; Robinson, 2006). Bayard de Volo, Reynolds, Sonsthagen, Talbot, and Antolin (2013) reported some genetic structure in mitochondrial DNA across North America, but did not include northern goshawks from Haida Gwaii Until recently, most such analyses of genetic variation in a conservation context have used a small set of molecular markers (e.g., mitochondrial DNA, which is inherited as a single unit from the mother; or a small number, e.g., 5–20, of microsatellite loci). Most such analyses of genetic variation in a conservation context have used a small set of molecular markers (e.g., mitochondrial DNA, which is inherited as a single unit from the mother; or a small number, e.g., 5–20, of microsatellite loci) These approaches may not reveal true population differences because the portion of the genome that differs between biological groups can be quite limited, even between groups that are morphologically distinct (Mason & Taylor, 2015; Toews, Taylor, et al, 2016). The overall goal of our study was to provide clarity to conservation managers regarding the number, distributions, and genetic distinctiveness of different forms of northern goshawk in northwestern North America
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