Data from: Small coastal streams – critical reservoirs of genetic diversity for brown trout in the face of increasing anthropogenic stressors

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
characterised 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.