The interplay between dispersal and gene flow in anadromous Arctic char (<i>Salvelinus alpinus</i>): implications for potential for local adaptation

Abstract

Dispersal can influence the process of local adaptation, particularly when the dispersers successfully breed in the non-natal habitat. Anadromous Arctic char (Salvelinus alpinus) display a complex migratory behaviour that makes the distinction between breeding and nonbreeding dispersal especially important. This species does not reproduce every year, but individuals must migrate to fresh water to overwinter such that a large proportion of fish running up-river are not in breeding condition and have no potential for gene flow. We used a genetic assignment approach to identify dispersers among populations of char from Baffin Island, Canada. Estimates of dispersal varied between 15.8% and 25.5% depending on the assignment method, suggesting that Arctic char disperse at a higher rate than other salmonids. Nonbreeding individuals were more likely to use non-natal habitats than breeding individuals, thus resulting in estimates of dispersal that overestimate the potential for gene flow among populations. Finally, we parameterized a population genetic model showing that gene flow is probably sufficiently low to allow for local adaptation among populations, given realistic selection coefficients. Our results underscore the importance of understanding patterns of dispersal to appropriately evaluate their potential consequences for local adaptation and management.