Conservation biology and genetic structure of fringe populations of the scarce heath butterfly in Sweden
Abstract: During the past century, about 82% of meadows and pastures have been lost in Sweden, with negative consequences for their flora and fauna. An example is the scarce heath butterfly, which is one of the red-listed species threatened by such habitat loss through afforestation. The main aim of this thesis was to study how the scarce heath may be affected by the ongoing loss of habitat and fragmentation. Another aim was to study how the globally peripheral and isolated position of the Swedish populations contributed to the genetic variability and differentiation of the species in Northern Europe. Mark-release-recapture techniques, habitat surveys, breeding experiments and molecular genetic analyses were used to address these questions.Genetic variability was lower in the Swedish populations than populations in more central parts of its distribution. At a local scale, the occurrence and local abundance of the scarce heath were correlated with patch size and isolation, and the abundance of certain plant species. Populations within a six km2 area showed significant genetic differentiation, and small and isolated populations expressed signs of inbreeding depression. Mark-release-recapture studies indicated that mobility between patches was restricted, and the species seemed to disperse primarily in a stepping-stone like fashion. However, the genetic differentiation did not follow an isolation-by-distance pattern. This discrepancy may be due to the relatively recent changes of the landscape. If the ongoing loss of habitat is not stopped and reversed, there is risk of a chain reaction of local extinctions, which may entail collapse of the whole metapopulation.
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