Survival of the endangered butterfly Lycaena helle in a fragmented environment: Genetic analyses over 15 years

Temporal changes in allele frequencies are often assumed in studies addressing the history of populations affected by different anthropogenic and natural impacts at different time scales. Yet, few studies directly compare the genetic composition of populations over time spans of more than 10 years. Therefore, to test the genetic effects of 15 years of population isolation in the butterfly Lycaena helle, we analysed 472 individuals from 27 samples, of which nine were collected in 1991 and 18 in 2006. Sampling was performed in five mountain regions (Pyrenees, Massif Central, Jura, Vosges and Ardennes). Genetic analyses were performed using five polymorphic microsatellites. Old and new samples of identical or neighbouring populations revealed similar genetic differentiations among these five mountain regions. A comparatively strong genetic differentiation among populations combined with a high amount of private alleles for each mountain area was detected, but mountain‐specific alleles were in most cases identical in 1991 and 2006. Nevertheless, the obtained data also indicate moderate changes between 1991 and 2006 in the species’ genetic structure – genetic differentiation among local populations increased marginally and allele frequencies showed corresponding modifications. A significant decline in genetic diversity was not detectable, and nine private alleles exclusive to a single mountain region were only detected in samples from the year 1991, whereas eleven were only observed in the individuals collected in 2006. These observations might indicate the results of genetic drift within isolated populations.