Population genomic analyses reveal a highly differentiated genetic cluster of northern goshawks (Accipiter gentilis laingi) in Haida Gwaii

Abstract

Accurate knowledge of geographic ranges and genetic relationships among populations is important when managing a species or population of conservation concern. In the western Canadian province of British Columbia, a subspecies of the northern goshawk (Accipiter gentilis laingi) is designated as Threatened under the Canadian Species at Risk Act. Historically, the range of this bird of prey has been ambiguous and its genetic distinctness from the other North American subspecies (Accipiter gentilis atricapillus) has not been well established. Given the uncertainty in using morphological traits to assign individual goshawks to these two subspecies, we analyzed genomic relationships in tens of thousands of single nucleotide polymorphisms identified using genotyping-bysequencing of high-quality genetic samples. This genome-wide analysis revealed a genetically distinct population of northern goshawks on the archipelago of Haida Gwaii and subtle genetic structuring among the remainder of our sampling sites within North America. Following from this analysis, we developed targeted genotyping assays for ten loci that are highly differentiated between the two main genetic clusters, allowing the addition of hundreds of low-quality samples to our analysis. This additional information confirmed that the distinct genetic cluster on Haida Gwaii is restricted to that archipelago. As the laingi form was originally described as being based in Haida Gwaii, where the type specimen of that form is from, further study (especially of morphological traits) may indicate a need to restrict this name to the Haida Gwaii genetic cluster.Regardless of taxonomic treatment, our finding of a distinct Haida Gwaii genetic cluster along with the small and historically 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. We anticipate that 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. otherwise differentiated populations) are unclear, efforts to conserve one of those forms are greatly complicated.Northern goshawks (Accipiter gentilis) living along the coast of British Columbia, Canada, and southeast Alaska, USA, provide an example of a species with unclear boundaries between forms that differ in their conservation status listing. Taverner (1940) determined that northern goshawks from the Haida Gwaii archipelago (called the Queen Charlotte Islands at the time) were more darkly colored than those from the mainland, whe...

Cryptic and extensive hybridization between ancient lineages of American crows

“…Today, Northwestern and American crow mtDNA haplogroups overlap across most of coastal Washington and all of coastal British Columbia, consistent with post‐glacial expansion of previously isolated populations into newly available habitat during one or more interglacial periods. Further sampling of crows on Haida Gwaii, the Alexander Archipelago, and other putative northern refugia might uncover additional genetic diversity within the Northwestern mtDNA haplogroup, which would corroborate the Pleistocene refugia hypothesis (e.g., Geraldes et al, 2019; Krosby & Rohwer, 2009).…”

“…During the late Pleistocene, when American and Northwestern mtDNA are estimated to have diverged ~ 443,000 years ago, North America was undergoing extensive glacial advances and retreats at regular ~ 100,000‐year Croll‐Milankovich intervals (Clark et al, 2009; Muller & MacDonald, 1997). Much of the Pacific Northwest was covered in ice sheets during the glacial periods, isolating terrestrial organisms south of the ice sheets or in ice‐free northern refugia such as Beringia, Haida Gwaii, or the Alexander Archipelago (Anderson, Hu, Nelson, Petit, & Paige, 2006; Burg, Gaston, Winker, & Friesen, 2006; Galbreath & Cook, 2004; Geraldes et al, 2019; Godbout, Fazekas, Newton, Yeh, & Bousquet, 2008; Shafer, Cullingham, Côté, & Coltman, 2010). During the interglacial periods, terrestrial organisms expanded from refugial populations into newly ice‐free habitats, leading to secondary contact and potentially renewed gene flow between closely related, previously allopatric forms (Shafer et al, 2010).…”

Long-term population decline of a genetically homogenous continental-wide top Arctic predator

“…2018), Bald Eagle Haliaeetus leucocephalu; F ST = 0.037-0.203 (Judkins et al . 2019), and Northern Goshawk Accipiter gentilis; F ST = 0-0.093 (Geraldes et al . 2019).…”

Extreme sex chromosome differentiation, likely driven by inversion, contrasts with mitochondrial paraphyly between species of crowned sparrows

“…The samples were genotyped using a genotyping-by-sequencing (GBS) procedure first described by Elshire et al (2011) with modifications described in Alcaide et al (2014) and Geraldes et al (2019). We prepared two GBS libraries with a 400-500 bp fragment size.…”