Small coastal streams-Critical reservoirs of genetic diversity for trout (Salmo trutta L.) in the face of increasing anthropogenic stressors.

R Andrew King,Bruce Stockley,Jamie R Stevens

doi:10.1002/ece3.6306

R Andrew King, Bruce Stockley + Show 1 more

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https://doi.org/10.1002/ece3.6306

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Abstract

We used microsatellite markers to investigate levels and structuring of genetic diversity in trout (Salmo trutta L.) sampled from 16 rivers along the south coast of Cornwall in southwest England. This region is characterized by many small coastal streams with a few larger catchments. At a regional level, genetic structuring of contemporary populations has been influenced by a combination of events, including the last Ice Age and also more recent human activities over the last millennium. All populations are shown to have gone through strong genetic bottlenecks, coinciding with increased exploitation of mineral resources within catchments, beginning during the Medieval period. At more local levels, contemporary human‐induced habitat fragmentation, such as weir and culvert construction, has disproportionally affected trout populations in the smaller catchments within the study area. However, where small catchments are relatively unaffected by such activities, they can host trout populations with diversity levels comparable to those found in larger rivers in the region. We also predict significant future loses of diversity and heterozygosity in the trout populations inhabiting small, isolated catchments. Our study highlights how multiple factors, especially the activity of humans, have and continue to affect the levels and structuring of genetic diversity in trout over long timescales.

Highlights

Identifying patterns of intraspecific genetic diversity and investigating the processes that generate such patterns is a central tenet of molecular ecology and conservation genetics
In a study of particular relevance to the topic, Spielman, Brook, and Frankham (2004) explored the impact of genetic factors on extinction risk for threatened populations and species and articulated the idea that reduced population genetic diversity correlates with reduced reproductive fitness and an elevated risk of future extinction linked to genetic factors
There is a disproportionately large number of these streams in southwest England, where the Devon/Cornwall peninsula precludes the development of large dendritic catchments and it has been suggested that the relatively small populations of trout residing in such small streams may collectively make a significant contribution to the genetic diversity of the species, in relation to those fish exhibiting an anadromous life cycle (Consuegra et al, 2005; Whelan, 2014), albeit with the caveat that small populations increase the effects of genetic drift, often leading to distinct but genetically depauperate populations (e.g., Paris, King, & Stevens, 2015; Perrier, Ferchaud, Sirois, Thibault, & Bernatchez, 2017)

Summary

| INTRODUCTION

Identifying patterns of intraspecific genetic diversity and investigating the processes that generate such patterns is a central tenet of molecular ecology and conservation genetics. There is a disproportionately large number of these streams in southwest England, where the Devon/Cornwall peninsula precludes the development of large dendritic catchments and it has been suggested that the relatively small populations of trout residing in such small streams may collectively make a significant contribution to the genetic diversity of the species, in relation to those fish exhibiting an anadromous (sea trout) life cycle (Consuegra et al, 2005; Whelan, 2014), albeit with the caveat that small populations increase the effects of genetic drift, often leading to distinct but genetically depauperate populations (e.g., Paris, King, & Stevens, 2015; Perrier, Ferchaud, Sirois, Thibault, & Bernatchez, 2017).

| MATERIALS AND METHODS

Findings

| DISCUSSION