Aim Three paradigm patterns of post-glacial dispersal are known for terrestrial species in Europe. However, the possibility of a fourth arises with the Italian and the Balkan lineages expanding to central Europe and the Iberian one being trapped by the Pyrenees. We test this hypothesis by analysing the molecular biogeography of the Marbled White butterfly.
Location Twelve populations distributed over a major part of the European range of Melanargia galathea and M. lachesis.
Methods We studied 18 allozyme loci of 403 individuals from 12 populations. Butterflies were sampled in the field, frozen in liquid nitrogen and stored under these conditions until analysis. We used cellulose acetate plates for allozyme electrophoresis.
Results We detected three major genetic lineages within the M. galathea/lachesis complex. The M. lachesis sample from the southern Pyrenees was strongly genetically differentiated from M. galathea (FCT: 0.312). Melanargia galathea splits into two major genetic lineages (FCT: 0.115), which both were found in post-glacially invaded regions. The further differentiation within these lineages was comparably low (FSC: 0.028). The genetic diversity within populations was high compared with other butterfly species.
Main conclusions Our findings support the existence of a fourth pattern with only the Iberian lineage not contributing considerably to the post-glacial colonization of central Europe. Preliminary studies in other butterfly species of dry grasslands support the importance of this pattern possibly representing a fourth paradigm. The high genetic diversity within populations might be one reason for the recently observed expansions at the northern distribution limits.