The genetic consequences of different dispersal behaviours in lycaenid butterfly species.

Many studies in population ecology have shown that related species have different dispersal behaviours. Species with sedentary and migratory behaviour exist in butterflies. While the genetic responses to population isolation are well studied, the effects of different dispersal behaviours of species are widely unknown. Therefore, we analysed 19 allozyme loci of two lycaenid butterflies, Cupido minimus as a sedentary butterfly and Aricia agestis as a mobile and expansive species. We collected 594 individuals (280 of C. minimus and 314 of A. agestis) in a western German study region with adjacent areas in Luxembourg and northeastern France. The genetic differentiation among populations of A. agestis (FST=3.9%) was lower than in C. minimus (FST=5.6%). Both species built up an isolation-by-distance system, which is more pronounced in A. agestis than in C. minimus. The genetic diversity in C. minumus populations (e.g. Ptot=73.5%) is higher for all analysed parameters than in A. agestis (e.g. Ptot=52.1%). Both species show specific genetic characteristics fitting with their different dispersal behaviours and respective ecological strategies. In the light of conservation genetics, we deduce that highly fragmented populations do not necessarily have a high extinction probability, but this risk depending much more on specific population genetic structures. In the studied species, C. minimus preserves a complex genetic constitution by high population densities. The patchily distributed A. agestis represents less rare alleles, present only in some populations, and holds up genetic diversity by high mobility.