Genetic consequences of an introduction-colonization process in an endangered butterfly species

From a theoretical point of view, the genetic consequences of foundation events are relatively well known but few field experimental data are available on this subject. At the beginning of the 1970s, a small number of Proclossiana eunomia females were released in a region where this glacial relict was absent. We report here the genetic aspects of the evolution of the populations generated by these translocations. Both enzyme electrophoresis and wing pattern morphometry disclosed a significant differentiation of the populations both with their mother population and within themselves. Field observations and enzyme data suggest a stepping-stone colonization process, but there is no significant isolation by distance at this stage of population establishment, as predicted by Slatkin's 1993 model. Concerning phenotypic characters, there is a significant correlation between morphometric and geographical distances; this may be due to isolation by distance but the action of environmental gradients cannot be excluded. Our results show that this colonization, although induced with a low number of founders, was a success, despite a predicted loss of polymorphism