Molecular phylogenetics of the moth genus Omiodes Guenée (Crambidae: Spilomelinae), and the origins of the Hawaiian lineage.

The moth genus Omiodes (Crambidae) comprises about 80 species and has a circumtropical distribution, with the type species, O. humeralis, occurring in Central America. In Hawaii, there are 23 native species currently placed in Omiodes, but this classification has been disputed, and they were previously placed in various other genera. We used molecular phylogenetic analyses to assess the monophyly of Omiodes as a whole, and specifically of the Hawaiian species, as well as their geographic origins and possible ancestral host plants. Mitochondrial (COI) and nuclear (wingless, EF1α, CAD, and RPS5) DNA was sequenced for Omiodes from Hawaii, South America, and Australasia, along with many other putative outgroup spilomeline genera. Phylogenies were estimated using maximum likelihood and Bayesian inference, and various taxon and character datasets. With the exception of two paleotropical species (O. basalticalis and O. odontosticta, whose placement was unresolved) all Hawaiian, paleotropical and neotropical Omiodes, including the type species, fell within a well-supported, monophyletic clade. Although the center of diversity for Omiodes is in the Neotropics, its center of origin was ambiguous, due to poor resolution of the basal splits between paleotropical and neotropical Omiodes. Very low genetic divergence within the Hawaiian Omiodes suggests a relatively recent colonization of the Hawaiian Islands. Phylogenies constructed using all codon positions were poorly resolved at intergeneric levels, and did not reveal a sister taxon for Omiodes, but phylogenies constructed using only first and second codon positions suggested a close relationship with Cnaphalocrocis. The monophyly of several other spilomeline genera is also discussed.