Strong genetic divergence indicates that congeneric damselflies Coenagrion puella and C-pulchellum (Odonata: Zygoptera: Coenagrionidae) do not hybridise

Coenagrionid damselflies are in general decline in the British Isles. Numerous factors have been implicated in the loss of these species including recent speculation that hybridisation between congeners may result in species decline. Here we use a panel of 12 microsatellite loci to examine levels of genetic divergence and the likely occurrence of hybridisation in five populations of Coenagrion puella and C. pulchellum using samples from four sites in south-east England. Coenagrion puella and C. pulchellum were highly genetically divergent, and there was no evidence of hybridisation between any of the populations examined, even where C. puella and C. pulchellum were sympatric. There was some suggestion that C. pulchellum was less genetically diverse than C. puella, though this may have been a result of ascertainment bias associated with cross-species application of microsatellite markers. We conclude that there is no evidence that hybridisation between C. puella/pulchellum could be responsible for the on-going demographic decline in C. pulchellum. Nevertheless, further genetic studies such as this one are likely to provide estimates of diversity, population structure and dispersal capacity that will be invaluable in future conservation management strategies for coenagrionid damselflies.