Phylogeographical lineages of Arctic grayling (Thymallus arcticus) in North America: divergence, origins and affinities with EurasianThymallus

Abstract

The number and location of Arctic glacial refugia utilized by taxa during the Pleistocene are continuing uncertainties in Holarctic phylogeography. Arctic grayling (Thymallus arcticus) are widely distributed in freshwaters from the eastern side of Hudson Bay (Canada) west to central Asia. We studied mitochondrial DNA (mtDNA) and microsatellite DNA variation in North American T. arcticus to test for genetic signatures of survival in, and postglacial dispersal from, multiple glacial refugia, and to assess their evolutionary affinities with Eurasian Thymallus. In samples from 32 localities, we resolved 12 mtDNA haplotypes belonging to three assemblages that differed from each other in sequence by between 0.75 and 2.13%: a 'South Beringia' lineage found from western Alaska to northern British Columbia, Canada; a 'North Beringia' lineage found on the north slope of Alaska, the lower Mackenzie River, and to eastern Saskatchewan; and a 'Nahanni' lineage confined to the Nahanni River area of the upper Mackenzie River drainage. Sequence analysis of a portion of the control region indicated monophyly of all North American T. arcticus and their probable origin from eastern Siberian T. arcticus at least 3 Mya. Arctic grayling sampled from 25 localities displayed low allelic diversity and expected heterozygosity (H(E)) across five microsatellite loci (means of 2.1 alleles and 0.27 H(E), respectively) and there were declines in these measures of genetic diversity with distance eastward from the lower Yukon River Valley. Assemblages defined by mtDNA divergences were less apparent at microsatellite loci, but again the Nahanni lineage was the most distinctive. Analysis of molecular variance indicated that between 24% (microsatellite DNA) and 81% (mtDNA) of the variance was attributable to differences among South Beringia, North Beringia and Nahanni lineages. Our data suggest that extant North American Arctic grayling are more diverse phylogeographically than previously suspected and that they consist of at least three major lineages that originated in distinct Pleistocene glacial refugia. T. arcticus probably originated and dispersed from Eurasia to North America in the late to mid-Pliocene, but our data also suggest more recent (mid-late Pleistocene) interactions between lineages across Beringia.

Population genetic structure of North American burbot (Lota lota maculosa) across the Nearctic and at its contact zone with Eurasian burbot (Lota lota lota)

“…The greater diversity found in the Mississippi subclade suggests that it harboured larger refugial population sizes during the Last Glacial Maximum relative to the other two refugia (Avise 2000). These three southern refugia are the source of many North American fish postglacial expansions (Rempel and Smith 1998;summarized in Turgeon and Bernatchez 2001;Stamford and Taylor 2004). Their exact location can only be generally known and surely varied during different times in glacial history (Bernatchez 1997;Rempel and Smith 1998).…”

Climate Change and the Molecular Ecology of Arctic Marine Mammals

“…Over the past two decades this phylogeographic approach (sensu Avise et al 1987) has illuminated the species and population histories of many high-latitude organisms (e.g., Bernatchez and Wilson 1998, Weider and Hobaek 2000, Stamford and Taylor 2004, including marine mammals. The star-like phylogenies of mtDNA lineages observed in beluga whales and the substantial phylogeographic partitioning of these lineages today argue that the origins of separate summering concentrations date back to postglacial expansion from refugial populations and indicate limited dispersal among these summering groups for long periods (Brennin et al 1997, Brown Gladden et al 1997.…”

Asymmetric admixture and morphological variability at a suture zone: parapatric burbot subspecies (Pisces) in the Mackenzie River basin, Canada

“…Barriers to gene flow tend to be asymmetric when there is a difference in fitness between groups (Barton & Hewitt, 1985) or expanding populations of ecologically similar taxa meet (e.g. Stamford & Taylor, 2004;Elmer et al, 2008). For example, Lu et al (2001) identified variable levels of introgression among glacial refugial groups of whitefish and argued that this reflected differential impacts of natural selection stemming from the use of different environments.…”