Genetic population structure of the Scotch argus butterfly (Erebia aethiops) in Britain : implications for conservation and future reintroduction

Gunson, Lucy and Menendez Martinez, Rosa and Roberts, Mike (2019) Genetic population structure of the Scotch argus butterfly (Erebia aethiops) in Britain : implications for conservation and future reintroduction. Masters thesis, Lancaster University.

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Abstract

Along with many other species, the Scotch argus (Erebia aethiops) has suffered a decline in range, particularly in England, with some populations experiencing long-term isolation. This thesis studied the genetic structure of the species in Britain on a national scale and at the metapopulation level with the aim of advising future management of the species and potential reintroductions across its former range in England. AFLP analysis carried out on populations from England, Scotland and the western Scottish islands found that there was no significant difference in genetic diversity between the regions. None of the study populations showed clear signs of inbreeding, suggesting inbreeding depression (a reduction in fitness due to inbreeding) is not a concern. Even those populations in England which were probably isolated for a long time (e.g. Arnside Knott) showed genetic diversity levels that were relatively high. However, populations were genetically differentiated with significant differences observed among both regions and populations. Genetic differences among populations were significantly related to geographic distance. On a local scale, the Smardale Gill metapopulation was found to be genetically robust with gene flow occurring between all patches. This was confirmed with a mark-release-recapture study which show that males are able to move long distances and the total population estimate for the whole area was high (over 7000 individuals). However, females moved only small distances, and none were reported to move between patches, suggesting that gene flow between patches is only maintained by males and colonisation of empty patches is limited. The results of this study provide support for several management recommendations for the conservation of the species. The struggling Arnside Knott population at the most southern range margin was found not to be suffering from inbreeding, so it is recommended that no supplementary translocations be made until the cause of the decline is determined. As populations were genetically differentiated, a geographically close population is recommended as a source to increase the chance of success of any future reintroduction. In this respect the Smardale Gill metapopulation appears the most suitable source for future reintroduction attempts across the species’ former range in England.