Local and Regional Population Genetic Structure of the Threatened Channel Darter in Ontario and Quebec

Genetic information can be a critical tool when designing recovery strategies for species at risk by informing spatial structure and diversity. The Channel Darter (Percina copelandi) is a small benthic fish with a naturally disjunct distribution that extends into central Canada (southern Ontario and Quebec), with additional fragmentation of some riverine populations by dams.  A number of Ontario and Quebec populations are presumed extirpated, and recent sampling suggests that populations in Lake Erie and Lake St. Clair are in decline.  Its disjunct distribution means that natural re-colonization of extirpated sites will likely not occur.  Re-establishment efforts need to identify the location of potential source populations and the number of individuals required to establish new, self-sustaining populations.  Ideally, source populations should possess similar genetic ancestry and diversity, as well as occupying similar ecological conditions to the re-establishment site. 

 To assess the genetic variation and relatedness of populations across its range, sampling trials tested the effectiveness of minimally invasive buccal swab sampling versus collecting fin clips for obtaining DNA.  Buccal swabs were found to provide DNA of sufficient quality and quantity for genotyping analysis and showed results consistent with that of fin clips.

 Channel darters from eight Ontario and Quebec populations were genotyped for ten microsatellite DNA loci and mitochondrial DNA (cytochrome-b) was sequenced.  The mitochondrial and microsatellite DNA both detected significant population differentiation among adjacent populations and across its Canadian range.  Remarkably, populations in southwestern Ontario and Quebec were more closely related than geographically intermediate populations in Lake Ontario tributaries.  In contrast to the observed regional population structure , analysis within the Trent and Salmon rivers showed no evidence of fragmentation or population substructuring resulting from the system of dams and locks, suggesting that either fish are able to circumnavigate barriers (in some cases) and/or that population genetic data do not yet reflect the physical fragmentation of these river systems.