Genomic dynamics of brown trout (Salmo trutta) populations released to a novel environment

• Population translocations occur for a variety of reasons, from displacement due to climate change, to human-induced transfers. Such actions have adverse effects on genetic variation and understanding their microevolutionary consequences requires monitoring. Here, we return to an experimental release of brown trout (Salmo trutta) in order to monitor genomic effects of population translocations. In 1979, fish from each of two genetically and ecologically separate populations were released at one point in time to the same lake system. Whole-genome sequencing data is used to characterize diversity within and divergence between introduced fish from different source populations and fish inhabiting two lakes down-stream of the release sites, sampled 30 years later (c. 5 generations). Diversity and divergence among introduced populations and fish sampled in the wild c. 5 generations later suggest extensive hybridization. Introduced fish are unequally represented in the lakes down-stream of the release sites, with fish from one population mainly contributing to the lake closest to the release site, and the fish from the other dominating the lake further downstream. We also identify genomic regions putatively under directional selection in the new lake system, where genes from one of the introduced populations, regulating metabolism, appear advantageous. Our results demonstrate that genetic effects of population translocations e.g., establishment, hybridization, and adaptation can be rapid after release into novel environments – even for a species with relatively small local effective population sizes and a large, complex genome. This is an important contribution to understanding the microevolutionary effects population translocations have on intraspecific diversity.  

Nyckelord

Population translocations

WGS

genetic monitoring

conservation genetics

hybridization

populationsgenetik

Population Genetics

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