Comparative Phylogeography of Salmonids in the British Isles: Implications for the Management of Biodiversity

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Intraspecific biodiversity underpins species' character and abundance. An understanding of its nature and distribution is needed by managers to develop effective programmes for conserving local fish stocks. Prior to 18,000 yrs bp, much of northern Europe was glaciated. The fish fauna of the British Isles, much of which was glaciated at the time, is dominated by salmonids and has largely evolved since this time. A comparative study was made of the distribution of mitochondrial DNA variation in Atlantic salmon, brown trout and Arctic charr based on restriction enzyme analysis of the D-loop, cytochrome b, and the ND1 gene regions of the mitochondrial genome. The study found all three species to display significant spatial diversity, both within and among river systems. Arctic charr populations and nonanadromous populations of brown trout showed the greatest spatial divergence, including major regional differences, as well as the lowest within population diversity. Significant divergence was also found for Atlantic salmon and anadromous brown trout, even between tributaries of the same river but with only limited regional differentiation. The implications of the work for understanding of the post-glacial evolution of biodiversity in salmonids in Europe, and the implications of the results for species management, are considered.