Allozyme variability in central, peripheral and isolated populations of the scarce heath (Coenonympha hero: Lepidoptera, Nymphalidae); implications for conservation

Genetic drift tends to lower geneticvariability in peripheral and isolatedpopulations. These populations also tend todiverge from more central populations if thedegree of isolation is high enough. Theseprocesses could have opposite effects on thevalue of the respective populations in thespecies conservation context. On the basis ofallozyme polymorphism data, we compare geneticvariability and differentiation between core,peripheral and isolated populations of thescarce heath, a butterfly endangered inNorthern and Central Europe. Genetic variationwas lowest in populations that were bothperipheral and isolated(P = 16.5%, Hobs = 0.017),and highest in the central populations(P = 35%,Hobs = 0.052). However, overall variability waslow also in the core area compared to that ofclosely related butterfly species. Theperipheral region was more differentiated fromthe other regions than the isolated region(FPC = 0.118, FPI = 0.257,FIC = 0.068). This study indicated thatisolation in combination with marginality havecaused an erosion of the gene pool. Theobserved patterns may be caused both by thecontemporary population structure of thespecies, as well as by the colonisationhistory. Both genetic and ecological evidencesuggests that the species is likely to followthe stepping-stone model of dispersal.