Exploring the evolution and diversity of Hawaii's endemic seed bugs, Nysius (Hemiptera: Lygaeidae)

The genus Nysius has a global distribution with 106 species, many of which are designated as agricultural pests. The 26 Hawaiian Nysius demonstrate more morphological diversity than is found in the rest of the Nysius species of the world. Most compelling about this Hawaiian genus is the presence of two wingless predator/scavenger species on Hawaii Island, an ecology found nowhere else. A phylogeny of this genus sheds light not only on the colonization and radiation of the genus throughout the entire Hawaiian archipelago, but it also creates a framework to study this extreme and rapidly derived feeding shift from herbivory to carnivory. Genetic sequence from three genes (COI, COII, EF1alpha) was used to construct a phylogeny of the genus in Hawaii. We have also included Nysius from New Zealand, French Polynesia, and the U.S. mainland as outgroups. Phylogenetic reconstructions were created using maximum parsimony and maximum likelihood analyses in PAUP* and RaXML software. The two predaceous species’ closest relatives are N. lichenicola and N. blackburni, both herbivores. The taxonomic status of some Hawaiian Nysius is in dire need of clarification. Our results provide the framework for reworking the diagnostic key and species assignments. We refute the 5 to 12 separate introductions to Hawaii as suggested by Usinger in 1942, and support the more recent idea of monophyly proposed by Ashlock (1982) and Polhemus (1998).