Data from: Rapid range expansion increases genetic differentiation while causing limited reduction in genetic diversity in a damselfly

Many ectothermic species are currently expanding their geographic range
due to global warming. This can modify the population genetic diversity
and structure of these species because of genetic drift during the
colonization of new areas. Although the genetic signatures of historical
range expansions have been investigated in an array of species, the
genetic consequences of natural, contemporary range expansions have
received little attention, with the only studies available focusing on
range expansions along a narrow front. We investigate the genetic
consequences of a natural range expansion in the Mediterranean damselfly
Coenagrion scitulum, which is currently rapidly expanding along a broad
front in different directions. We assessed genetic diversity and genetic
structure using twelve microsatellite markers in five centrally located
populations and five recently established populations at the edge of the
geographic distribution. Our results suggest that, although a marginal
significant decrease in the allelic richness was found in the edge
populations, genetic diversity has been preserved during the range
expansion of this species. Nevertheless, edge populations were genetically
more differentiated compared to core populations, suggesting genetic drift
during the range expansion. The smaller effective population sizes of the
edge populations compared to central populations also suggest a
contribution of genetic drift after colonization. We argue and document
that range expansion along multiple axes of a broad expansion front
generates little reduction in genetic diversity, yet stronger
differentiation of the edge populations.