Geographical variation in calling song of the field cricket Teleogryllus oceanicus: the importance of spatial scale

We compared calling songs of the field cricket Teleogryllus oceanicus from 15 sites within six regions of two continental areas, Oceania and Australia . The cricket was introduced to Hawaii, where it is subject to an acoustica lly orienting parasitoid fly not found elsewhere in its range. In a princip al components analysis (PCA) of song from all populations combined, the fir st five components had eigenvalues greater than one, and collectively accou nted for over 80% of the total variation. Means for all song components var ied significantly among sites, and different components varied at the three levels of analysis (continent, region and site). The principal way in whic h sites differed was along a gradient in increasing song length, pulse dura tion and intervals between song elements. Crickets from Oceania had a signi ficantly greater variance in their song than Australian crickets, driven la rgely by the high variance in Hawaii. Geography explained a substantial amo unt of variation in song, despite the likelihood of serial bottlenecks havi ng occurred as the species moved from island to island. Because female cric kets appear not to focus on the short chirp as a component of mate choice, a lack of selection may allow this song component to vary more widely.