Origin, diversity, and diversification of the native Hawaiian leafhoppers (Hemiptera: Cicadellidae: Nesophrosyne)

The native Hawaiian leafhopper genus Nesophrosyne (Hemiptera: Cicadellidae) is a diverse and ubiquitous, yet understudied, element of the Hawaiian entomofauna. The genus currently comprises seventy-two described species, showing single island endemicity across all high islands of the archipelago. Nesophrosyne species occur in almost all habitat types ranging from coastal scrub to sub-alpine regions, and nearly all species are native host-plant dependent, utilizing 75% of the most species rich and ecologically dominant plant genera (e.g., Clermontia, Coprosma, Pipturus, etc.). Our recent morphological and molecular analyses of over 300 taxa and 12 pacific-wide outgroups indicate a monophyletic Nesophrosyne that is three-times larger than its currently described diversity with over 200 species endemic to Hawaii. Preliminary phylogenetic results support a Kauai origin for extant Nesophrosyne, with a basal multi-island clade associated exclusively with the plant family Urticaceae, particularly the genera Urera and Pipturus. A bulk of the Nesophrosyne diversity is accounted for by a large subsequent radiation, involving multiple colonizations and radiations on other islands with transitions to novel host-plant families and genera. While host-plant switching appears to be common for some Nesophrosyne species, there is evidence for major host-plant transitions giving rise to monophyletic groups associated with Broussaisia, Dodonea, Coprosma, Myrsine and Melicope (among others). Large clades associated with Coprosma, Broussaisia and Pipturus, spanning multiple islands, provide a window into the evolutionary forces driving Nesophrosyne diversification. The progression rule (species colonizing progressively younger islands) emerges as a common pattern, however some clades demonstrate more complicated scenarios of island colonization and speciation.