Host-plants shape insect diversity: phylogeny, origin, and species diversity of native Hawaiian leafhoppers (Cicadellidae: Nesophrosyne).

Herbivorous insects and the plants on which they specialize, represent the most abundant terrestrial life on earth, yet their inter-specific interactions in promoting species diversification remains unclear. This study utilizes the discreet geologic attributes of Hawai'i and one of the most diverse endemic herbivore radiations, the leafhoppers (Hemiptera: Cicadellidae: Nesophrosyne), as a model system to understand the role of host-plant use in insect diversification. A comprehensive phylogeny is reconstructed to examine the origins, species diversification, and host-plant use of the native Hawaiian leafhoppers. Results support a monophyletic Nesophrosyne, originating from the Western Pacific basin, with a sister-group relationship to the genus Orosius. Nesophrosyne is characterized by high levels of endemicity according to individual islands, volcanoes, and geologic features. Clades demonstrate extensive morphologically cryptic diversity among allopatric species, utilizing widespread host-plant lineages. Nesophrosyne species are host-plant specific, demonstrating four dominant patterns of specialization that shape species diversification: (1) diversification through host switching; (2) specialization on widespread hosts with allopatric speciation; (3) repeated, independent shifts to the same hosts; and, (4) absence or low abundance on some host. Finally, evidence suggests competing herbivore radiations limit ecological opportunity for diversifying insect herbivores. Results provide evolutionary insights into the mechanisms that drive and shape this biodiversity.