Geomorphological and climatic processes drove the evolution and population genetic differentiation of brook trout

Brook trout Salvelinus fontinalis is a popular sportfish native to North America and introduced worldwide, as well as an indicator of environmental quality. We review published studies and synthesize a view of how geomorphological, climatological, and ecological factors gave rise to the current distribution of brook trout and the geographic patterning of its population genetic diversity. Phylogenetic studies show that the center of diversity for charrs – i.e., members of Genus Salvelinus – is east Asia and northwestern North America and that divergence of most Salvelinus species occurred during the Miocene Epoch. Members of the Salvelinus lineage dispersed throughout northern Canada and eastern North America, the contemporary natural distribution of brook trout, perhaps with the opening of the Bering Strait at ~5.3 mya near the end of the Miocene Epoch or perhaps earlier through the Paleo-Bell River system. The contemporary population genetic structure of brook trout was patterned by retreat to refugia from Pleistocene glaciation, followed by Holocene recolonization of eastern North America. That is, contemporary populations of brook trout represent the descendants of fish from Acadian, Mid-Atlantic, or Mississippian refugia and from recent mixing upon secondary contact. Population genetic variation mostly conforms to watershed boundaries, a finding that informs fisheries and conservation management strategies. A growing body of research provides insights into local adaption of brook trout populations. The future viability of many populatons of brook trout will depend upon implementation of well-considered, conservation-oriented management actions. • Fossil salmonids date to 50 Ma in the Pacific Northwest of North America. • Brook trout arose around 9 Ma, and colonized eastern North America via the Bering Strait or the Paleo-Bell River system. • Neutral genetic variation reflects expansion of populations from three glacial refugia. • Recent research demonstrates adaptive genetic variation within and among brook trout populations.