Identification of a barrier height threshold where brook trout population genetic diversity, differentiation, and relatedness are affected

The overall goal of the study was to evaluate effects of landscape features, barriers, on Brook Trout Salvelinus fontinalis population genetics and to identify a potential barrier height threshold where genetic diversity was reduced upstream of the barrier and differentiation and relatedness increase. We screened variation at eight microsatellite DNA loci within Brook Trout populations upstream and downstream of ten putative natural barriers ranging in height from 1.5 to 61 m to quantify allelic variation, differentiation (F-ST), individual assignment probability (Q), and relatedness (r(xy)). Average gene diversity per locus (H), differentiation (F-ST), and mean relatedness values (r(xy)) became significantly greater in relation to barrier height starting at 4 m according to piecewise linear regression. This potential barrier height threshold is greater than the barrier height criterion identified for Brook Trout based on physical criteria and jumping ability (0.74 m). The 4 m barrier-height criteria can be used to identify barrier sites where Brook Trout populations may be at risk due to reduced genetic diversity and increased relatedness.