Identification and Characterization of Cuticular Hydrocarbons from a Rapid Species Radiation of Hawaiian Swordtailed Crickets (Gryllidae: Trigonidiinae: <Emphasis Type="Italic">Laupala</Emphasis>)

A previous investigation of cuticular hydrocarbon variation among Hawaiian swordtail crickets (genus Laupala) revealed that these species differ dramatically in composition of cuticular lipids. Cuticular lipid extracts of Laupala species sampled from the Big Island of Hawaii also possess a greatly reduced number of chemicals (as evidenced by number of gas chromatography peaks) relative to ancestral taxa sampled from the geologically older island of Maui. One possible explanation for this biogeographic pattern is that reduction in chemical diversity observed among the Big Island taxa represents the loss of ancestral hydrocarbons found on Maui. To test this hypothesis, we characterized and identified the structures of cuticular hydrocarbons for seven species of Hawaiian Laupala, two from Maui (ancestral) and five from the Big Island of Hawaii (derived) by using gas chromatography-mass spectrometry. Big Island Laupala possessed a reduced number of alkenes as well as a reduction in the diversity of methyl-branch positions relative to species sampled from Maui (ancestral), thus supporting our hypothesis of a founder-induced loss of chemical diversity. The reduction in diversity of ancestral hydrocarbons was more severe within one of the two sister lineages on the Big Island, suggesting that post-colonizing processes, such as drift or selection, also have influenced hydrocarbon evolution in this group.