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

Abstract

Whether natural or man-made, landscape features often influence the patterns of genetic variation within a species and can have important conservation implications. This is especially true for Brook Trout Salvelinus fontinalis, which are typically restricted to high-quality headwater streams. In this study, we characterized the patterns of genetic partitioning and diversity among Brook Trout populations in the Laurel Hill of southwestern Pennsylvania with respect to landscape features and potential barriers to migration. In total, 354 wild Brook Trout samples collected across 10 streams were analyzed using 12 microsatellite loci. Our results showed a wide range of genetic diversity (allelic richness A R = 3.404-7.124; expected heterozygosity H e = 0.432-0.727) and effective population size estimates (N e = 13.5-1,106.6) and indicated that some sites contained small, low-diversity populations of Brook Trout. Three populations were located upstream of reservoirs; however, our results did not show significant differences in the genetic diversity metrics between upstream and downstream populations. Although isolation by distance could be a factor, the patterns of genetic differentiation revealed minimal contemporary gene flow between watersheds and among most streams. Overall, our results highlight the need for continued population monitoring and habitat restoration for Brook Trout populations in southwestern Pennsylvania.

A novel quantitative framework for riverscape genetics

“…We highlighted the utility of our framework and the increased predictive performance of the BGR model in a study of brook trout riverscape genetics. Numerous population genetic studies have suggested that brook trout populations isolate at small spatial scales, including isolation of neighboring tributaries with no known movement barrier (Kazyak et al 2016, Beer et al 2019). This, along with behavioral observations, has led many to assume that brook trout can have limited dispersal ability, particularly when intervening habitat consists of larger rivers that are only seasonally habitable.…”

Genetic predictors of population resilience: A case study of native Brook Trout in headwater streams

“…The negative relationship we observed between F IS and F ST and the reactivity envelope metric would support that higher F IS and F ST result in greater resistance to change. High levels of inbreeding and isolation could be a consequence of population fragmentation (Beer et al 2019). Brook Trout populations have been observed to respond to isolation with high juvenile survival and faster generation times (Letcher et al 2007) potentially accounting for the positive relationship we observed between F IS and F ST and resistance metrics.…”

“…High levels of inbreeding and isolation could be a consequence of population fragmentation (Beer et al. 2019). Brook Trout populations have been observed to respond to isolation with high juvenile survival and faster generation times (Letcher et al.…”

Conservation genetics of the endangered California Freshwater Shrimp (Syncaris pacifica): watershed and stream networks define gene pool boundaries

“…In networks of streams and rivers, physical settings such as elevation, drainage configuration, unidirectional water flow, limited lateral connectivity and extreme hydrological events (ex. droughts, floods) all influence population size and gene flow (Bohonak and Jenkins 2003;Crispo et al 2006;Díez-del-Molino et al 2016Beer et al 2019;Whelan et al 2019). Human activities such as agriculture, urbanization, and dams also tend to reduce genetic connectivity among populations (Horreo et al 2011;Roberts et al 2013;Beer et al 2019;Richmond et al 2018).…”

“…droughts, floods) all influence population size and gene flow (Bohonak and Jenkins 2003;Crispo et al 2006;Díez-del-Molino et al 2016Beer et al 2019;Whelan et al 2019). Human activities such as agriculture, urbanization, and dams also tend to reduce genetic connectivity among populations (Horreo et al 2011;Roberts et al 2013;Beer et al 2019;Richmond et al 2018). For these reasons, freshwater systems tend to have a higher density of threatened species than marine and terrestrial systems (Dudgeon et al 2006;Strayer and Dudgeon 2010).…”