Microsatellite analysis of brook trout, Salvelinus fontinalis, in western Pennsylvania

Abstract

In western Pennsylvania, the brook trout, Salvelinus fontinalis, has dramatically declined in population due to the environmental stressors of mining, logging, water withdrawal, and acid deposition. Brook trout are game fish and are valued economically in this region which makes their declining populations concerning. To better understand brook trout population dynamics in western Pennsylvania, we conducted a genetic analysis to determine patterns of population connectivity and genetic diversity. Microsatellites are short repeat sequences within the genome, and are highly susceptible to mutation making them suitable as neutral markers for analyzing patterns of regional population variation. Therefore, we conducted a microsatellite analysis of 16 individuals from 4 streams, for a total of 64 samples. Seven tri-and tetranucleotide microsatellite DNA markers were analyzed to investigate allelic diversity of brook trout. Amplified microsatellite loci were analyzed using Geneious 6.0 software that estimated PCR product sizes and converted sizes into estimates of the number of microsatellite repeats at each locus. Genepop 4.2 program was used to obtain the fixation index (FST) to measure levels of population differentiation and connectivity. The results showed moderate divergence (average pairwise divergence FST= 0.24; range of 0.06-0.30) with highly significant differentiation (P < 0.001). My study suggests that even populations that are spatially close to one another show evidence of divergence. This finding suggests limited dispersal between streams and will inform species management strategies for this species.