Genetic consequences of range expansions along several fronts in Crocothemis erythraea


Global warming has altered the ranges of many species, especially those of insects and other ectotherms that are particularly susceptible to rising temperatures. Four decades ago, the dragonfly Crocothemis erythraea began to demonstrate northern range expansion in Germany, as well as in Belgium, the Netherlands, Poland and the UK. The rapid range expansion of C. erythraea has highlighted the capacity of this dragonfly for dispersal, making this species a good model to investigate the genetic consequences of expansions from several fronts. We predict that the recently established populations of C. erythraea in central Europe (Germany & Switzerland) will show only a minimal reduction in genetic diversity (because founders may derive from a broader set of core populations) with respect to populations from core regions of this species, and an increase in the genetic differentiation (given the multiple independent expansion axes along the broad front). To test our hypothesis, we compared genetic variation, in terms of genetic diversity and genetic differentiation using two mitochondrial genes (cytochrome b and NADH dehydrogenase), between central Europe and three core regions (south-west Europe, Italy and Africa). Results were in concordance with our hypothesis: populations from central Europe did not show a significant reduction in the overall genetic diversity but were highly differentiated from Africa, Italy and south-west Europe populations.

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