Genetic analysis of Dolly Varden (Salvelinus malma) across its North American range: evidence for a contact zone in southcentral Alaska

Abstract

Contact zones between divergent lineages of aquatic taxa have been described from the northeastern Pacific Ocean. We surveyed samples of Dolly Varden (Salvelinus malma) from their North American range for variation at 14 microsatellite DNA loci. After accounting for hybridization between Dolly Varden and co-occurring bull trout (Salvelinus confluentus) and Arctic char (Salvelinus alpinus), we found evidence for two genetic lineages of Dolly Varden consistent with the previously recognized subspecies, northern Dolly Varden (S. m. malma) and southern Dolly Varden (S. m. lordii). We documented a contact zone between the two subspecies from the eastern Alaska Peninsula to Cook Inlet, Alaska, where admixture values (i.e., the proportion of the genome estimated to be composed of northern Dolly Varden, Q NDV ) ranged between Q NDV = 0.245 and 0.754 across about 700 ocean kilometres. Populations of Dolly Varden showing low admixture (i.e., less than 5%) were located a minimum of 346 km to the west to 1200 km to the southeast, respectively, from the contact zone. The two lineages of Dolly Varden probably stem from isolation and subsequent divergence in, and dispersal from, distinct northern and southern Pleistocene glacial refugia and substantiate the treatment of S. malma as two subspecies and as at least two designatable units under Canada's Species at Risk Act.

Low levels of hybridization between sympatricArctic char (Salvelinus alpinus) andDollyVarden char (Salvelinus malma) highlights their genetic distinctiveness and ecological segregation

“…The Dolly Varden from BC are a different subspecies ( S. malma lordi ) than the Egegik Dolly Varden ( S. m. malma , see review by Kowalchuk et al. 2010; Taylor and May-McNally 2015), but the results of simulations using either subspecies did not change and we gained the advantage of knowing that the BC Dolly Varden are allopatric with respect to Arctic char. Next, these reference populations were designated as “learning samples” by implementing the USEPOPINFO model combined with simulated hybrids and char from Lake Aleknagik and Lake Nerka through five replicated analyses in STRUCTURE (Pritchard et al.…”

Life-history characteristics and landscape attributes as drivers of genetic variation, gene flow, and fine-scale population structure in northern Dolly Varden (Salvelinus malma malma) in Canada

“…In North America, the northern Dolly Varden occurs as anadromous and fluvial forms in the western Arctic of Canada, the North Slope of Alaska, and south to at least the northward draining (Bering Sea) drainages along the Alaska Peninsula (Behnke 1980;Reist et al 1997;DeCicco and Reist 1999;Taylor and May-McNally 2015). Along the Alaska Peninsula, northern and southern Dolly Varden from the northeastern Pacific form a contact zone (as revealed in microsatellite DNA analyses; Taylor and May-McNally 2015). Throughout its range, Dolly Varden exhibit prominent variation in demographic characteristics COSEWIC 2010), including sympatric anadromous and resident (nonmigratory riverine) forms (Reist 1989;Everett et al 1997).…”

Introgressive hybridization between two phylogenetic lineages of charrs ( Salvelinus : Salmonidae) in northeastern Asia

“…In some cases, secondary contact could lead to historical introgressive hybridization between lineages (Radchenko, 2004b; Redenbach & Taylor, 2002; Taylor & May‐McNally, 2015; Wilson & Bernatchez, 1998; Yamamoto et al, 2006). One of the most interesting consequences of the secondary contact emerges in the fixation of the historical hybridization in the regions where one of the participating taxa is not present nowadays.…”