Evolutionary Dynamics of Behavioral Divergence among Populations of the Hawaiian Cave-dwelling Planthopper Oliarus polyphemus (Homoptera: Fulgoroidea: Cixiidae)

Abstract

The cixiid genus Oliarus has undergone extensive adaptive radiation on the Hawaiian Islands, with 80 described endemic species descending from an initial successful colonization by a single ancestral species. In Hawaiian Oliarus, however, adaptive radiation is not restricted to surface habitats. Several evolutionary lines have invaded lava tubes independently on the islands of Molokai, Maui, and Hawaii. Populations of one of the cave invasions on the island of Hawaii, the blind, flightless, and pigmentless species Oliarus polyphemus Fennah, have been found in numerous lava tubes within four of the five volcanoes on the island. Recent investigations on mating behavior, especially the analysis of the substrate-borne courtship signals of several O. polyphemus populations, revealed a high degree of divergence: the signals of all seven cave populations studied differ significantly. Because these signals serve formate recognition within species of planthoppers, we regard the O.polyphemus populations studied to be reproductively isolated (i.e., representing separate biological species). Hypotheses to explain this high degree of divergence among O. polyphemus populations are discussed.