Geographic Variation in the Lateral Line Scale Counts of the Arctic Grayling, Thymallus arcticus

Abstract

An examination of Arctic grayling (Thymallus arcticus) collected on either side of the continental divide (Brooks Range) in Alaska revealed that lateral line scale counts were significantly higher on the North Slope than in the Yukon Basin to the south. An examination of geographic variation in this character within the North American range of the species suggested a division into three geographic areas: an area of uniformly low mean counts in the Bering Sea–North Slope of Alaska; an area of uniformly high counts in the remainder of Alaska and parts of the Yukon Territory and British Columbia; an area of variable mean counts in the Northwest Territories. Only two glacial refugia need be postulated to explain this pattern if it is assumed that populations in the first and last of these areas have a similar Mississippian origin and the high count populations a Beringian origin.

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

“…McCart & Pepper (1971) described so‐called ‘large’‐ and ‘small’‐scale phenotypes of T. arcticus distributed north and south of the Brooks Range in Alaska. Although we did not study mtDNA variation from the same populations, our documentation of mtDNA haplotype groups A and B, that also roughly coincide with a division north and south of the Brooks Range is consistent with the idea that Arctic grayling survived glaciation in two isolated regions in Beringia (i.e.…”

“…These observations, coupled with high genetic diversity within populations carrying group B mtDNA along the Arctic coast and apparently low mtDNA diversity in Montana (Redenbach & Taylor 1999) suggest that these extant Montana were founded by North Beringia grayling. The Montana grayling appear phenotypically intermediate, however, between the large‐ and small‐scale forms of T. arcticus (McCart & Pepper 1971) and the greatest proportion of genetic variance at microsatellite loci occurred among groups when Saskatchewan populations (that share haplotypes at high frequency with Montana grayling) were treated as a separate group. These subtle differences suggest that although these southern and eastern populations of Arctic grayling probably owe their ultimate origin to dispersal from North Beringia during early Pleistocene glaciations, they may have originated most recently by survival in and dispersal from southern Great Plains refugia during the last glaciation (cf.…”

“…A sample located further downstream in the Mackenzie River, closer to the Peel River contained only mtDNA lineage B haplotypes (Keel River, Table 2). In addition, Arctic grayling with the large‐scale phenotype that was associated with mtDNA group B (North Beringia) are found in the Peel River north of the Nahanni River (McCart & Pepper 1971; Bodaly & Lindsey 1977). Both these observations suggest a North Beringia lineage origin for grayling found between the Nahanni River Valley and the Arctic Ocean rather than the existence of a second, more northern refuge in the Mackenzie River area.…”

“…Arctic grayling in Montana, however, are genetically distinct from grayling in the northern part of the species’ range (Lynch & Vyse 1979; Redenbach & Taylor 1999), which suggests that they may represent descendants of fish that survived the Pleistocene glaciations in the Great Plains (upper Missouri River) glacial refuge (Lindsey & McPhail 1986). In addition, morphological evidence suggests that there are two distinct lineages in northwestern North America; north and south of the Brooks Range in the Alaskan portion of Beringia (McCart & Pepper 1971; Reed 1973). There is also evidence that points to an inland glacial refuge (Nahanni Refuge) that harboured freshwater fish in the Northwest Territories (Lindsey et al .…”

Comparative biology and management of Arctic and European grayling (Salmonidae, Thymallus)

“…Significantly different meristic characteristics were recognized in grayling from the Yukon basin and north slope (Arctic) drainages, suggesting their multiple origin in at least two glacial refugia (McCart and Pepper, 1971). Shortly thereafter, several groups of isozyme phenotypes were found in grayling (Massaro, 1973) and such biochemical genetic analysis was used to indicate significant differences in Alaskan populations (Phillip, 1983).…”