Hybridization between invasive and native species, a significant threat to worldwide biodiversity, is predicted to increase due to climate‐induced expansions of invasive species. Long‐term research and monitoring are crucial for understanding the ecological and evolutionary processes that modulate the effects of invasive species. Using a large, multidecade genetics dataset (
- Award ID(s):
- 1652278
- NSF-PAR ID:
- 10318973
- Date Published:
- Journal Name:
- Science Advances
- Volume:
- 7
- Issue:
- 52
- ISSN:
- 2375-2548
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract As humans cause the redistribution of species ranges, hybridization between previously allopatric species is on the rise. Such hybridization can have complex effects on overall fitness of native species as new allelic combinations are tested. Widespread species introductions provide a unique opportunity to study selection on introgressed alleles in independent, replicated populations. We examined selection on alleles that repeatedly introgressed from introduced rainbow trout (
Oncorhynchus mykiss ) into native westslope cutthroat trout (Oncorhynchus clarkii lewisi ) populations in western Canada. We found that the degree of introgression of individual single nucleotide polymorphisms from the invasive species into the native is correlated between independent watersheds. A number of rainbow trout alleles have repeatedly swept to high frequency in native populations, suggesting parallel adaptive advantages. Using simulations, we estimated large selection coefficients up to 0.05 favoring several rainbow trout alleles in the native background. Although previous studies have found reduced hybrid fitness and genome‐wide resistance to introgression in westslope cutthroat trout, our results suggest that some introduced genomic regions are strongly favored by selection. Our study demonstrates the utility of replicated introductions as case studies for understanding parallel adaptation and the interactions between selection and introgression across the genome. We suggest that understanding this variation, including consideration of beneficial alleles, can inform management strategies for hybridizing species. -
Success of stream restoration can be difficult to define because many interacting abiotic and biotic factors across spatio‐temporal scales can have measurable effects. Consequently, failure in habitat restoration to achieve targeted biological goals may reflect interactions of habitat restoration with unaccounted risks that have yet to be addressed on the landscape. This is particularly true within invaded landscapes, where habitat restoration can benefit non‐native competitors as much as the native fishes for which restoration is designed. We tested for interacting effects of a reach scale habitat restoration effort and non‐native trout competition on habitat use by a brook trout (
Salvelinus fontinalis ) metapopulation within a productive main stem corridor of the Shavers Fork watershed, West Virginia. We used a joint species occupancy model within a BACI sampling design to show that brook trout occupancy of main stem habitat was highest post‐restoration within restored sampling reaches, but this benefit to native brook trout was conditional on brown trout (Salmo trutta ) not being present within the main stem habitat. Collectively these results indicate that habitat restoration was only beneficial for native brook trout when non‐native trout were absent from the restored sampling area. Proactive approaches to restoration will be integral for supporting resilient ecosystems in response to future anthropogenic threats (e.g. climate change), and we have shown that such actions will only be successful if non‐native competitors do not also benefit from the restoration actions. -
Abstract The invasion of freshwater ecosystems by non‐native species can constitute a significant threat to native species and ecosystem health. Non‐native trouts have long been stocked in areas where native trouts occur and have negatively impacted native trouts through predation, competition, and hybridization. This study encompassed two seasons of sampling efforts across two ecoregions of the western United States: The Great Basin in summer 2016 and the Yellowstone River Basin in summer 2017. We found significant dietary overlaps among native and non‐native trouts within the Great Basin and Yellowstone River Basin ecoregions. Three orders of invertebrates (Ephemeroptera, Trichoptera, and Diptera) composed the majority of stomach contents and were responsible for driving the observed patterns. Great Basin trout had higher body conditions (k), and non‐native Great Basin trout had higher gut fullness values than Yellowstone River Basin trout, indicating a possible limitation of food in the Yellowstone River Basin. Native fishes were the least abundant and had the lowest body condition in each ecoregion. These findings may indicate a negative impact on native trouts by non‐native trouts. We recommend additional monitoring of native and non‐native trout diets, regular invertebrate surveys to identify the availability of diet items, and reconsidering stocking efforts that can result in overlap of non‐native fishes with native cutthroat trout.
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As molecular techniques become more advanced, scientists and practitioners are calling for restoration to leverage genetic and genomic approaches. We address the role of genetics in the restoration and conservation of cutthroat trout in the western United States, where new genetic insights have upended previous assumptions about trout diversity and distribution. Drawing on a series of examples, we examine how
genetically pure trout populations are identified, protected, and produced through restoration practices. In landscapes that have been profoundly impacted by human activities, genetics can offer seemingly objective metrics for restoration projects. Our case studies, however, indicate that (1) genetic purity is fragile and contingent, with notions of what genetics are “pure” for a given species or subspecies continually changing, and (2) restoration focused on achieving “genetically pure” native populations can deliberately or inadvertently obscure the socioecological histories of particular sites and species, even as (3) many “genetically pure” trout populations have endured on the landscape as a result of human modifications such as roads and dams. In addition to raising conceptual questions, designations of genetic purity influence policy. These include tensions between restoring connectivity and restoring genetic purity, influencing Wild and Scenic River Act designations, and the securing of water rights. Cutthroat trout restoration would benefit from adopting a broader, more holistic framework rather than fixating exclusively or primarily on genetic purity and hybridization threats.