Hawaiian Courtship Songs: Evolutionary Innovation in Communication Signals of Drosophila

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Abstract
In Hawaii, flies of the genus Drosophila have undergone spectacular adaptive radiation, resulting in the evolution of more than 500 species of Drosophila that are found nowhere else on earth. This taxonomic uniqueness is reflected in behavior and morphology. Hawaiian Drosophila sing songs, as do continental Drosophila; however, the Hawaiian songs have diverged strongly in form and mechanism of production. The click-song of D. fasciculisetae's (Maui) has a carrier frequency an order of magnitude higher than those reported in familiar continental species, such as D. melanogaster (170 hertz). Drosophila fasciculisetae's song resembles a cicada's more than a fly's song. The song of D. cyrtoloma (Maui) has a complex pulse rhythm more typical of crickets than flies. The pulse song of D. silvestris (Hawaii) closely resembles that of D. melanogaster in both pulse rhythm and carrier frequency, but D. melanogaster sings by vibrating its wings, whereas D. silvestris sings through abdominal vibrations. These mechanisms are radical departures from the continental wing song mechanism and are further examples of the remarkable behavioral innovation that has occurred in the Drosophila of Hawaii during their evolutionary transit through these islands.