Abstract
Establishing true phylogenetic relationships between populations is a critical consideration when sourcing individuals for translocation. This presents huge difficulties with threatened and endangered species that have become extirpated from large areas of their former range. We utilise ancient DNA (aDNA) to reconstruct the phylogenetic relationships of a keystone species which has become extinct in Britain, the Eurasian beaver Castor fiber. We sequenced seventeen 492 bp partial tRNAPro and control region sequences from Late Pleistocene and Holocene age beavers and included these in network, demographic and genealogy analyses. The mode of postglacial population expansion from refugia was investigated by employing tests of neutrality and a pairwise mismatch distribution analysis. We found evidence of a pre-Late Glacial Maximum ancestor for the Western C. fiber clade which experienced a rapid demographic expansion during the terminal Pleistocene to early Holocene period. Ancient British beavers were found to originate from the Western phylogroup but showed no phylogenetic affinity to any one modern relict population over another. Instead, we find that they formed part of a large, continuous, pan-Western European clade that harbored little internal substructure. Our study highlights the utility of aDNA in reconstructing population histories of extirpated species which has real-world implications for conservation planning.
Highlights
Reintroduction programs are an essential tool in the restoration of viable, free-ranging populations[1] but over 50 percent result in failure[2]
Recent evidence from ancient DNA has uncovered a huge decrease in genetic diversity within C. fiber, which is wholly attributed to anthropogenic influences and which has created the artificial pattern of strong population structure observed in remnant extant populations[26]
The second specimen from Gough’s Cave, MM004 (11,989-11,405 cal BP), falls within the Younger Dryas range, the range on the date extends into the earliest Holocene
Summary
Reintroduction programs are an essential tool in the restoration of viable, free-ranging populations[1] but over 50 percent result in failure[2]. In 2011, the Enclosed Beaver Project was initiated, which saw a mating pair, of unknown/unpublished origin, released into a captive site in Western Devon[19] The success of these populations, combined with favourable feasibility studies[20,21], indicate that large-scale reintroductions to Britain may be initiated soon. Any British beaver reintroduction program must, consider the ancestral relationship of the source population/s to the original British population in addition to factors such as, i) the relative merits of selecting founders from single versus multiple populations, ii) mixing individuals from disparate clades, iii) levels of pre-existing genetic diversity in the source population/s and iv) the potential for inbreeding or outbreeding depression. Ancient DNA allows the sampling of populations that have become regionally extinct and cannot be included in studies that utilize DNA from extant populations alone[30,31] as is the case with British populations of C. fiber
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