Human mining activity across the ages determines the genetic structure of modern brown trout (Salmo trutta L.) populations.

Josephine R Paris,R Andrew King,Jamie R Stevens

doi:10.1111/eva.12266

Abstract

Humans have exploited the earth's metal resources for thousands of years leaving behind a legacy of toxic metal contamination and poor water quality. The southwest of England provides a well-defined example, with a rich history of metal mining dating to the Bronze Age. Mine water washout continues to negatively impact water quality across the region where brown trout (Salmo trutta L.) populations exist in both metal-impacted and relatively clean rivers. We used microsatellites to assess the genetic impact of mining practices on trout populations in this region. Our analyses demonstrated that metal-impacted trout populations have low genetic diversity and have experienced severe population declines. Metal-river trout populations are genetically distinct from clean-river populations, and also from one another, despite being geographically proximate. Using approximate Bayesian computation (ABC), we dated the origins of these genetic patterns to periods of intensive mining activity. The historical split of contemporary metal-impacted populations from clean-river fish dated to the Medieval period. Moreover, we observed two distinct genetic populations of trout within a single catchment and dated their divergence to the Industrial Revolution. Our investigation thus provides an evaluation of contemporary population genetics in showing how human-altered landscapes can change the genetic makeup of a species.

Highlights

The exploration for and exploitation of metals have played a crucial role in human history
We found that metal-impacted populations have reduced genetic diversity compared to relatively unaffected control populations from clean rivers
Our genetic diversity calculations showed that Hayle trout have significantly reduced variation compared to all other populations studied

Summary

Introduction

The exploration for and exploitation of metals have played a crucial role in human history. Metals are natural constituents of the earth’s crust (Wedepohl 1991), their prevalence within natural systems has been significantly enhanced by human activity (Han et al 2002). Metals are extremely persistent in the environment; they are nondegradable, and readily accumulate at toxic levels. Mining for such metals has a rich history in Britain. Large areas of southwest England have been mined since the Bronze Age (2500 BCE: Dines 1956; Buckley 2002), with increasing exploitation during the Roman occupation (McFarlane et al 2013), and later, as technology improved, throughout the Medieval period

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