Genetic variability and structuring of Arctic Charr (Salvelinus alpinus) populations in northern Fennoscandia

Abstract

Variation in presumably neutral genetic markers can inform us about evolvability, historicaleffective population sizes and phylogeographic history of contemporary populations. We studied genetic variability in 15 microsatellite loci in six native landlocked Arctic charr (Salvelinusalpinus) populations in northern Fennoscandia, where this species is considered near threatened. We discovered that all populations were genetically highly (mean FST ≈0.26) differentiated and isolated from each other. Evidence was found for historical, but not for recent population size bottlenecks. Estimates of contemporary effective population size (Ne) ranged from seven to 228 and were significantly correlated with those of historical Ne but not with lake size. A census size (NC) was estimated to be approximately 300 individualsin a pond (0.14 ha), which exhibited the smallest Ne (i.e. Ne/NC = 0.02). Genetic variability in this pond and a connected lake is severely reduced, and both genetic and empirical estimatesof migration rates indicate a lack of gene flow between them. Hence, albeit currently thriving, some northern Fennoscandian populations appear to be vulnerable to further lossof genetic variability and are likely to have limited capacity to adapt if selection pressures change. Copyright: