Phylogeny of the grassland leafhopper genus Flexamia (Homoptera: Cicadellidae) based on mitochondrial DNA sequences

Leafhoppers (Cicadellidae) are a highly diverse group of sap-sucking insects, many species of which specialize on grasses. Past attempts to examine the roles of host transfer or host plant coevolution in the diversification of leafhopper species using cladistic methods have been hindered by a paucity of discrete, phylogenetically informative morphological characters. To demonstrate the utility of DNA sequence data for species-level phylogenetic studies of Cicadellidae, we estimated phylogenetic relationships among species in the North American grassland leafhopper genus Flexamia DeLong using partial nucleotide sequences of mitochondrial 16S rDNA and NADH dehydrogenase 1, totaling 1496 base pairs and 810 potentially informative characters. Analyses of the partitioned and combined sequence data using maximum parsimony, neighbor-joining, and maximum likelihood criteria yielded similar estimates of relationships in which most nodes were well-supported by bootstrap and decay indices. These estimates largely agreed with a previously published, intuitive, morphology-based phylogeny for the genus. A parsimony reconstruction of host associations based on these results suggests that the origins of various Flexamia clades coincided with host transfers among grass subfamilies or genera. Nevertheless, associations with certain subfamilies, genera, or species of grasses appear to have been largely conserved in the evolutionary diversification of Flexamia.