Coding Gene Single Nucleotide Polymorphism Population Genetics of Nonnative Brook Trout: The Ghost of Introductions Past

Abstract

Fish have been translocated throughout the world, and introductions often have been executed repeatedly and have used mixtures of different strains from the native range. This history might have contributed to their invasive potential by allowing introduced and invading populations to circumvent expected reductions in genetic diversity from founder effects in a scenario termed the "genetic paradox" of invasions. We characterize patterns of genetic diversity in nonnative Brook Trout Salvelinus fontinalis, which have been introduced across the western United States for over a century but have also invaded broadly and pose a primary threat to native trout. We analyzed 155 coding gene single nucleotide polymorphisms (SNPs) in 34 nonnative Brook Trout populations sampled across eight large river systems as well as samples from the only four hatchery strains with documented use in Idaho. We uncovered similar within-population genetic diversity and large effective population sizes in naturalized populations compared with hatchery samples. Naturalized populations also showed substantial genetic structuring (maximum pairwise F ST = 0.23) across and even within watersheds and indicated suggestions of admixture in certain regions. Assignment probabilities confirmed two main hatcheries as the origin of most fish collected in the field; however, the four hatcheries were excluded as being the origin for 8% of individuals, mirroring results from clustering analyses and suggesting the influence of an additional unsampled hatchery source or sources. Simulated admixtures of hatchery samples produced genetic patterns similar to those observed in field samples, further supporting an influence of multiple historic hatchery stocks on the contemporary genetic structure of Brook Trout in Idaho. Our study highlights the potential contribution of historic hatchery and introduction practices in creating genetically variable and structured naturalized Brook Trout populations across Idaho, which may have allowed these fish to defy the "genetic paradox" early on in their nonnative history and set the stage for successful establishment and subsequent invasion.

Genomic patterns of diversity and divergence of two introduced salmonid species in Patagonia, South America

“…For Brook Charr, Paradise Hatchery from North America was a probable source stock representing Lago Fagnano and Alonso River in the extreme southern end of Patagonia. This was consistent with expectations that Paradise Hatchery would be a possible source stock as it has been identified as a common source for broad introductions in other geographic regions outside the species’ range (Neville & Bernatchez, ). The other collections of Brook Charr from Patagonia were highly distinct from those in the native range in Quebec, Canada, which is consistent with the high level of genetic divergence commonly observed in this species (e.g., Marie et al., ).…”

Contrasting genetic metrics and patterns among naturalized rainbow trout (Oncorhynchus mykiss) in two Patagonian lakes differentially impacted by trout aquaculture

“…Our LD N b results are in line with findings showing higher genetic diversity for Lake Llanquihue and lower genetic diversity for Lake TLS. Artificially propagated populations resulting from multiple introduction events may show effective population sizes greater than naturally propagated ones as seen in introduced vendace Coregonus albula in Europe (Præbel et al., ) and brook trout in North America (Neville & Bernatchez, ). However, Narum et al.…”

“…Estimates for the effective number of breeders using LD (N b ) were larger for rainbow trout from Lake Llanquihue than from Lake TLS. (Praebel et al, 2013) and brook trout in North America (Neville & Bernatchez, 2013). However, Narum et al (2017) recently found that estimates of LD N b among Chinook salmon Oncorhynchus tshawytscha populations introduced in Patagonia were smaller than among native populations, suggesting that there may be exceptions to these findings.…”

Influence of Stream Condition on Habitat Diversity and Fish Assemblages in an Impaired Upper Snake River Basin Watershed

“…Brook Trout were abundant in the high-gradient, cold streams, whereas Cutthroat Trout and Rainbow Trout were abundant only in the moderate-gradient, cold sites that we sampled, a pattern also observed by Maret et al (1997) for least-disturbed streams in the upper Snake River basin. The mechanisms driving patterns of salmonid relative abundances requires further study, as those patterns could reflect negative competitive interactions (Peterson et al 2004;Benjamin et al 2011), hybridization (Meyer et al 2006), and stocking and invasion history (Benjamin et al 2007;Neville and Bernatchez 2013). Inconsistent capture of Rainbow Trout suggests this species has invaded only the lower portion of the watershed in streams nearest Lower Goose Creek Reservoir.…”