Phylogeny, evolution, and historical biogeography of the grassland leafhopper tribe Chiasmini (Hemiptera: Cicadellidae: Deltocephalinae)

The phylogeny, evolution, and biogeography of the grassland-associated leafhopper tribe Chiasmini (21 genera, 316 species) were investigated using phylogenetic analyses of two different data sets, one including 81 taxa and 3000 aligned nucleotide positions from the NADH dehydrogenase subunit1 (ND1), histone H3, 28SrDNAD2, and cytochromec oxidase subunitII (COII) gene regions, and one including 31 taxa and 3610 aligned nucleotide positions from the 28SrDNAD2-D10 and histone H3 gene regions. The results were equivocal regarding the monophyly of the tribe, apparently because of low phylogenetic signal towards the base of the tree; however, analyses of 81 taxa recovered two well-supported clades that together included all sampled Chiasmini. CladeI was resolved as (Leofa (Nephotettix, Exitianus)); cladeII included the remaining 13 sampled genera. Most relationships between genera and species of Chiasmini were strongly supported. Alternative scenarios previously proposed for the origin of the Exitianus obscurinervis species group in the New World were examined through phylogenetic dating and biogeographic analyses. A sister-group relationship between the Exitianus nanus and Exitianus obscurinervis species groups was recovered, and the results were consistent with a long-distance dispersal event from either the Afrotropical region or the Pacific islands into South America at a maximum of 34.3Mya, and subsequent invasion and diversification of the group in North America at a maximum of 17.9Mya. For the primarily North American genus Athysanella, the largest genus of the tribe (137spp.), the results indicate that some of the previously recognized subgenera are not monophyletic. Observations on the remarkable diversity in head shape and other morphological characters are made and compared with other grassland-inhabiting tribes of Deltocephalinae.