Elucidating the impact of anthropogenic supplementation, isolation and ecological heterogeneity on Brook Trout (Salvelinus fontinalis) genetic structure

Abstract

Preservation of genetic diversity is a commonly cited, yet under-evaluated aspect of species conservation plans. Understanding the influence of human-mediated translocations and habitat constraints on landscape patterns of genetic structure in threatened fish species is essential to maintaining biodiversity and adaptive potential. We evaluated the degree of influence from supplemental stocking, assessed the spatial population genetic structure, and examined the potential relationship between hybridization and ecology for Brook Trout (Salvelinus fontinalis) in the Black River watershed in New York State, USA. We used 13 microsatellite loci from over 450 fish at 18 sampling locations to map genetic structure and diversity, estimate the level of influence from stocked conspecifics, and model the relationship between hybridization and ecological characteristics. We found widespread genetic introgression attributable to state-based stocking activities and a pattern of hierarchical genetic diversity across the landscape, which has additionally been influenced by geography. Site-specific fish assemblage variables appear to be unrelated to introgressive hybridization from stocked conspecifics, and only one hydrochemical variable, SO42−, exhibited strong explanatory power in predicting hybridization between wild and supplemented fish. A single locality exhibited genetic structure consistent with no history of introgression potentially associated with differences in elevation, and thus contributed disproportionately to the level of genetic diversity observed across the landscape. When examining genetic structure in fluvial riverine networks, it is important to consider the combined and interacting effects of both hybridization and habitat, which may result in augmented genetic structure not predictable from any single factor.