Blue hawaiiense and Beyond: Conservation Genetics and Comparative Phylogeography of Four Hawaiian Megalagrion Damselfly Species (Odonata: Coenagrionidae)

Hawaii’s endemic Megalagrion damselflies are rivaled in their beauty and diversity only by the degree of threat posed to them by anthropogenic disturbance. In this preliminary study of phylogeography and conservation genetics, we have sequenced about 660 base pairs (bp) of the mitochondrial COII gene from 191 damselflies from four species, including 31 populations that span a gradient of endangerment. We applied phylogeographic analyses in order to understand their biogeographic history. Unlike Megalagrion xanthomelas and M. pacificum, M. calliphya and M. hawaiiense rarely share haplotypes between populations and between islands, even within the larger Maui Nui superisland, suggesting that these latter two species do not disperse as well across land or water. Their phylogenies also better reflect the geological history of the islands. We applied conservation genetic analyses in order to understand their genetic health. Under a conservation genetic paradigm, populations with low genetic diversity are generally considered to be at greater risk of decline and extinction than populations with high genetic diversity. Applying this principle to Megalagrion populations gave both expected and surprising results. Expected results included measurements of high diversity in most populations of M. calliphya, M. hawaiiense, and Hawai‘i Island populations of M. xanthomelas. Low diversity was observed in populations known to be bottlenecked or relictual, including O‘ahu and Maui M. xanthomelas, and M. pacificum. Surprising results included low genetic diversity in O‘ahu Ko‘olau and Hawai‘i Onomea M. hawaiiense, Moloka‘i M. pacificum, and West Maui M. calliphya. We propose that these latter three populations be monitored and managed to maximize their long-term genetic health.