Data from: Evolution and origin of sympatric shallow-water morphotypes of Lake Trout, Salvelinus namaycush, in Canada's Great Bear Lake

Range expansion in north-temperate fishes subsequent to the retreat of the
Wisconsinan glaciers has resulted in the rapid colonization of previously
unexploited, heterogeneous habitats and, in many situations, secondary
contact among conspecific lineages that were once previously isolated.
Such ecological opportunity coupled with reduced competition likely
promoted morphological and genetic differentiation within and among
post-glacial fish populations. Discrete morphological forms existing in
sympatry, for example, have now been described in many species, yet few
studies have directly assessed the association between morphological and
genetic variation. Morphotypes of Lake Trout, Salvelinus namaycush, are
found in several large-lake systems including Great Bear Lake (GBL),
Northwest Territories, Canada, where several shallow-water forms are
known. Here, we assess microsatellite and mitochondrial DNA variation
among four morphotypes of Lake Trout from the five distinct arms of GBL,
and also from locations outside of this system to evaluate several
hypotheses concerning the evolution of morphological variation in this
species. Our data indicate that morphotypes of Lake Trout from GBL are
genetically differentiated from one another, yet the morphotypes are still
genetically more similar to one another compared with populations from
outside of this system. Furthermore, our data suggest that Lake Trout
colonized GBL following dispersal from a single glacial refugium (the
Mississippian) and support an intra-lake model of divergence. Overall, our
study provides insights into the origins of morphological and genetic
variation in post-glacial populations of fishes and provides benchmarks
important for monitoring Lake Trout biodiversity in a region thought to be
disproportionately susceptible to impacts from climate change.