Reassessment of Dalbulus leafhopper (homoptera: cicadellidae) phylogeny based on mitochondrial DNA sequences

Conflicting hypotheses of phylogenetic relationships among leafhopper species in the genus Dalbulus DeLong have resulted from analyses of morphological and allozyme data. To improve the phylogenetic estimate, nucleotide sequence data from 340 bp of the mitochondrial 12S rDNA gene and 942 bp of the NADH dehydrogenase 1 (ND1) gene were compiled for 10 species of Dalbulus, 1 species of its putative sister group. Baldulus, and 2 outgroups. Intraspecific branch lengths were estimated for Dalbulus gelbus DeLong. Dalbulus maidis (DeLong and Wolcott), and Baldulus tripsaci Kramer and Whitcomb. Sequences were aligned based on secondary structure models of the 12S gene and along codons in the ND1 gene. Phylogenetic analyses of the sequence data using maximum parsimony, genetic distance-neighbor joining and maximum likelihood methods yielded nearly identical results. A test for incongruence indicated that the phylogenetic estimate based on sequence data was not significantly different from that derived based on morphological characters. Allozyme data yielded a topology that was significantly incongruent with both morphological and sequence data. Therefore, the morphological and sequence datasets were combined into a single analysis, which yielded a well-resolved phylogenetic estimate for Dalbulus. The resulting tree supports the hypothesis that the ancestral hosts of Dalbulus were gamagrasses (Tripsacum spp.) and that the acquisition of a preference for maize (Zea mays) arose independently in 2 Dalbulus lineages.