Geographic influences on fine-scale, hierarchical population structure in northern Canadian populations of anadromous Arctic Char (Salvelinus alpinus)

Abstract

Assessments of fine-scale population struc- ture in natural populations are important for understand- ing aspects of ecology, life history variation and evolu- tionary history and can provide novel insights into re- source management. Although Arctic char, Salvelinus alpinus, represent one of the most culturally and com- mercially important salmonids in the Canadian Arctic, fine-scale assessments of genetic structure in northern populations of this species are rare. In this study, we assessedpopulationstructure inanadromousArcticchar from Cumberland Sound in Canada's Nunavut territory using 18 microsatellite loci. Specifically, we aimed at identifying potential habitat and landscape/geographic features influencing genetic variation and population structure and resolving potential barriers to gene flow. Overall population structure was moderate (global FST and Jost's D of 0.042 and 0.236 respectively) and sig- nificant among all sampling locations. Habitat and land- scape/geographic features, with the exception of fluvial (shoreline) distance, appeared to have little influence on genetic variation and population structure. Bayesian clustering revealed a hierarchical model of population structure, in which the 14 sampling locations were nested within two distinct clusters corresponding to the north and south shores of Cumberland Sound. Both isolation-by-distance analysis and calculations of mean dispersal distance suggest dispersal and gene flow is highest among proximate locations. Finally, several pu- tative barriers to gene flow were identified and one, a putative barrier separating north and south Cumberland Sound, was consistent with the hierarchical STRUC- TURE results. Our results suggest that the current river-specific management of commercially harvested Arctic char is appropriate. Overall, we provide further insights into the evolution of genetic variation and pop- ulation structure in iteroparous, Arctic salmonids.