GENETIC-STRUCTURE OF FRENCH POPULATIONS OF THE MOUNTAIN BUTTERFLY PARNASSIUS-MNEMOSYNE L (LEPIDOPTERA, PAPILIONIDAE)

Geographical variation in allozyme frequencies among 24 populations of the butterfly Pamassius mnemosyne in southern France was studied by e nzyme electrophoresis. Clustering procedures were used to define the g eographical organization of genetic variation and an analysis of genet ic differentiation was performed to test the degree of potential gene flow between the colonies using the methodologies derived from F-stati stics and the private alleles model. Further, an approach using reduce d space ordinations (factorial analysis of correspondences and discrim inant analysis), was used to allow the visualization of genetically in termediate populations and to determine the roles of individual allele s at various levels of geographical structure. In P. mnemosyne, the ef fect of both isolation by distance and geographical barriers upon gene flow is complex. Some barriers appear to be very efficient, but other s, at least as strong geographically, do not act in such a way. Multiv ariate analyses underlined the progressive transition between some gro ups while in other instances, a sharp cut was observed without obvious topographical barriers. Ecogeographical data and historical events (s uch as colonization processes) should probably be taken into account i n order to explain the geographical variation of genetic structure.