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

Genetic drift tends to lower genetic variability in peripheral and isolated populations. These populations also tend to diverge from more central populations if the degree of isolation is high enough. These processes could have opposite effects on the value of the respective populations in the species conservation context. On the basis of allozyme polymorphism data, we compare genetic variability and differentiation between core, peripheral and isolated populations of the scarce heath, a butterfly endangered in Northern and Central Europe. Genetic variation was lowest in populations that were both peripheral and isolated (P = 16.5%, Hobs = 0.017), and highest in the central populations (P = 35%, Hobs = 0.052). However, overall variability was low also in the core area compared to that of closely related butterfly species. The peripheral region was more differentiated from the other regions than the isolated region (F-PC = 0.118, F-PI = 0.257, F-IC = 0.068). This study indicated that isolation in combination with marginality have caused an erosion of the gene pool. The observed patterns may be caused both by the contemporary population structure of the species, as well as by the colonisation history. Both genetic and ecological evidence suggests that the species is likely to follow the stepping-stone model of dispersal.