Microsatellite variation and genetic structure of brook trout (Salvelinus fontinalis) populations in Labrador and neighboring Atlantic Canada: evidence for ongoing gene flow and dual routes of post‐Wisconsinan colonization

Abstract

In conservation genetics and management, it is important to understand the contribution of historical and contemporary processes to geographic patterns of genetic structure in order to characterize and preserve diversity. As part of a 10-year monitoring program by the Government of Newfoundland and Labrador, Canada, we measured the population genetic structure of the world's most northern native populations of brook trout (Salvelinus fontinalis) in Labrador to gather baseline data to facilitate monitoring of future impacts of the recently opened Trans-Labrador Highway. Six-locus microsatellite profiles were obtained from 1130 fish representing 32 populations from six local regions. Genetic diversity in brook trout populations in Labrador (average HE= 0.620) is within the spectrum of variability found in other brook trout across their northeastern range, with limited ongoing gene flow occurring between populations (average pairwise FST= 0.139). Evidence for some contribution of historical processes shaping genetic structure was inferred from an isolation-by-distance analysis, while dual routes of post-Wisconsinan recolonization were indicated by STRUCTURE analysis: K= 2 was the most likely number of genetic groups, revealing a separation between northern and west-central Labrador from all remaining populations. Our results represent the first data from the nuclear genome of brook trout in Labrador and emphasize the usefulness of microsatellite data for revealing the extent to which genetic structure is shaped by both historical and contemporary processes.

Microsatellite and mtDNA analysis of lake trout, Salvelinus namaycush, from Great Bear Lake, Northwest Territories: impacts of historical and contemporary evolutionary forces on Arctic ecosystems

“…; Pilgrim et al. ). This may be especially true for systems recently colonized post‐glacially by founding populations with extremely large historical effective sizes where drift is essentially negligible.…”

“…Historical gene flow and the retention of ancestral polymorphisms have been implicated in the lack of differentiation and obscured contemporary population structure in a variety of other northern and Arctic salmonids (e.g., Harris and Taylor ; Pilgrim et al. ). Pronounced historical gene flow in this study is evidenced by the lack of differentiation at mtDNA between Sandy and GBL lakes (sharing of common haplotypes between these systems), although these two systems are clearly isolated from each other based on microsatellite DNA analysis.…”

Genetic Assessment Reveals Population Fragmentation and Inbreeding in Populations of Brook Trout in the Laurel Hill of Pennsylvania

“…High population differentiation is common among Brook Trout and has been documented in many other studies, even when barriers to fish movement are minimal (Pilgrim et al. ; Kelson et al. ; Bruce et al.…”

“…This habitat restriction has resulted in a large degree of genetic structuring among stream‐dwelling Brook Trout populations (Pilgrim et al. ; Kelson et al. ; Bruce et al.…”

Discordance between nuclear and mitochondrial DNA analyses of population structure in closely related triplefin fishes (Forsterygion lapillum and F. capito, F. Tripterygiidae) supports speciation with gene flow

“…Another finding in our data is that the gradient of diversity between North and South Island populations evident in the mtDNA data is much reduced. Gradients of diversity attributed to glaciation on the basis of mtDNA data that were much less obvious in microsatellite data have been seen in other fishes (Pilgrim et al 2012). This suggests that the imprint of glaciation is much less discernible at microsatellite loci.…”