Molecular systematics and phylogeography of Hawaii's Megalagrion damselflies

Date of Completion

January 2001


Biology, Entomology




I have used mitochondrial and nuclear DNA sequence data to explore the phylogenetic relationships of species in Hawaii's marvelous Megalagrion damselfly radiation. These damselflies occupy a wide diversity of habitats. Results indicated that Megalagrion species relationships agree with some hypotheses of previous workers. In particular the monophyly of several species groups was supported by the molecular data, and traditional taxonomy appears to be adequate. However, molecular data also contradicted and clarified the established notions in several key ways. First, two sequential bursts of evolution may have been responsible for the some of the remarkable ecological diversity in the genus. Analysis of mitochondrial DNA under a local molecular clock suggested that these rapid speciation events coincided with the emerging availability of suitable habitats on Kauai and Oahu. Second, the traditional problematic phylogenetic placement of several species is probably due to the rapid pace of the radiation that produced these species, leaving few informative characters on key internal branches. The phylogeography of the species M. xanthomelas and M. pacificum was explored using mitochondrial sequence data from 157 individual damselflies. I sought to understand the demographic and historical processes responsible for the current distribution of genetic variation in these two species, and found that current patterns of female genetic diversity correspond to Pleistocene island connections. Finally, I evaluated the usefulness of three different methods for performing Nested Clade Analysis (NCA), with reference to real and theoretical examples. Data from Hawaiian damselflies indicate that Method 2 NCA is susceptible to problems when population sample sizes are small or unbalanced, and when hypothesized population boundaries vary. ^