Sympatric divergence in Arctic charr: Genetic and morphological evidence

Background/Question/Methods

Arctic charr (Salvelinus alpinus) frequently show a trophic polymorphism within
lakes which is related to their habitat (benthic or pelagic). In this study we examined
morphological and genetic differences within and between 7 loch populations in
Scotland- 4 polymorphic and 3 monomorphic.

Results/Conclusions

Geometric morphometric analysis confirmed a priori classifications of the two morphs within lochs, as well as revealing
strong morphological differences between lochs. Structure analysis of 10
microsatellite loci revealed almost complete partitioning of benthic and pelagic
morphs. However, variation at ND1 and control region genes in mitochondrial (mt)
DNA showed no clear pattern of structuring between or within lochs. These results
suggest that that differentiation has arisen in situ, rather than as a consequence of
historical patterns of recolonization of lakes from different glacial refugia. The
lack of gene flow as well as the morphological differences observed, suggest that
reproductive isolation may interact with environmental variables to produce frequent
ecological adaptation within charr populations.