Population Genetics of Arctic Grayling Distributed Across Large, Unobstructed River Systems

Abstract

We investigated the population genetics of Arctic Grayling Thymallus arcticus distributed throughout several connected river systems in Alberta, Canada. Broad- and fine-scale population structure was examined by genotyping nine microsatellite loci in 1,116 Arctic Grayling captured from 40 sites in the Hay, Peace, and Athabasca River basins. Genetic diversity tended to decline from north to south (allelic richness versus latitude: Spearman's rank correlation r_s = 0.793, P < 0.05); the lowest level of diversity was detected in a stocked population. We found significant genetic divergence between and within major river basins (overall genetic differentiation index F_ST [θ_ST] = 0.13) and strong isolation-by-distance patterns in the Peace River basin (Mantel's r = 0.97, P < 0.001) and Athabasca River basin (Mantel's r = 0.95, P < 0.001). Evidence for gene flow among sites in neighboring rivers (i.e., 25–100 km apart) was common; significant genetic differentiation tended to occur at the subbasin level. The spatial scale of differentiation for Arctic Grayling is intermediate to those reported for other sympatric salmonid species that differ in population size and degree of spawning site fidelity.

Received September 24, 2013; accepted January 15, 2014

ACKNOWLEDGMENTS

Support for this research was provided by the Alberta Conservation Association; Natural Sciences and Engineering Research Council of Canada; Canadian Wildlife Federation; Alberta Sport, Recreation, Parks, and Wildlife Foundation; Golder Associates Ltd.; Northern Lights Fly Tyers/Trout Unlimited Edmonton Chapter; Edmonton Old Timers Fishing Club; and the Canadian Circumpolar Institute, University of Alberta (a Circumpolar/Boreal Alberta Research grant funded by the office of the University of Alberta's Vice-President of Research; and a Northern Scientific Training Program grant funded by Aboriginal Affairs and Northern Development Canada through the Canadian Polar Commission). Tissue samples were provided by Alberta Environment and Sustainable Resource Development and by the Northern Lights Fly Tyers/Trout Unlimited Edmonton Chapter. We thank F. Noddin for assistance in the field and C. Davis, J. Miller, and S. Dang for assistance in the laboratory. We also thank two anonymous reviewers for their comments on an earlier version of this manuscript. Fish collection by University of Alberta staff was conducted in accordance with guidelines approved by the University of Alberta's Animal Care and Use Committee (Protocol Number 758/09/13) and was permitted under provincial fish research licenses (License Numbers 12-2003 FRL, 12-0437 FRL, and 12-1201 FRL).