Genetic Characteristics of Southern and Northern Brook Trout (Salvelinus fontinalis) Populations at the Zone of Contact

Abstract

Population genetic evidence suggests differentiation among evolutionarily significant units of southern and northern Appalachian brook trout, with the zone of contact in southwestern Virginia. Before this differentiation was recognized, brook trout of northern origin were stocked throughout the southeastern United States. In order to determine this differentiation, established allozyme markers were used to classify 56 southwest Virginia populations as southern, northern, or introgressed. Variation at 4 polymorphic loci, including the diagnostic creatine kinase (CK-A2*) locus, indicated that 19 populations were of southern origin, 5 of northern origin, and 32 of mixed genetic origin. Data compiled among genetic studies of brook trout in the southern Appalachians showed that the southern/northern break is sharp, occurring at the New/Roanoke-James watershed divide. New River drainage populations exhibited the southern allele at high frequency, suggesting their historic native character as southern, with presence of northern alleles due to stocking or stream capture events. In conclusion, the present study suggests that management of southern Appalachian brook trout should include: (1) genetically cognizant planning of stocking events, (2) management of populations on a stream-by-stream basis, (3) prioritized conservation of pure southern brook trout populations, and (4) use of southern Appalachian hatchery stocks in restoration efforts.

Population Genetics of Brook Trout in the Southern Appalachian Mountains

“…We did not find evidence for a crisp genetic break between putative northern and southern lineages at the New River watershed (Printz et al. 2018). Rather, we interpret the southern cluster as the descendants of fish radiating from a Pleistocene refugium in the Mississippi River drainage, which colonized much of North America west of the ECDD, with evidence of dispersal as far north as Pennsylvania and New York.…”

“…1993; Printz et al. 2018). Our findings based on microsatellite allele frequencies support the distinctiveness of Brook Trout in the southern Appalachian Mountains, which may be explained, in part, by a zoogeographic boundary along the ECDD.…”

“…These studies fostered a widespread perspective that southern Appalachian Brook Trout represent a distinct entity (i.e., “northern” versus “southern” strains), with a sharp transition area near the New River drainage (Figure 1; Palmer and Hallerman 2000; Davis 2008; Printz et al. 2018; S. Guffey, 1998 unpublished report to the Virginia Department of Game and Inland Fisheries on population genetics of Brook Trout in Virginia) and potentially even warranting a taxonomic revision (Stoneking et al. 1981).…”

“…2018; Printz et al. 2018), possibly resulting in a loss of regional diversity and local adaptations (Laikre et al. 2010).…”

“…1993; Printz et al. 2018), allowing us to assess the putative genetic break between “northern” and “southern” Brook Trout at the New River drainage and to identify other zones of discontinuity where they occur. This information may help to provide the foundation for ongoing conservation and management activities across the region.…”