TEMPORAL SYNCHRONY AND PATTERNS IN AN EXOTIC HOST-PARASITOID COMMUNITY

We studied an imported host-parasitoid community in Hawaii, asking to what extent the species covaried in a systematic fashion even though a ll species were exotic to Hawaii, and occurred in an artificial agro-e cosystem (a commercial guava, Psidium guajava L., orchard), Using knoc k-down pyrethrin sprays we were able to accurately quantify numbers of the host, [oriental fruit fly, Bactrocera dorsalis (Hendel)] and its four major parasitoid species [Biosteres arisanus (Sonan), Diachasmimo rpha longicaudata (Ashmead), Psyttalia incisi (Silvestri), and Bi. van denboschi (Fullaway)] at hourly intervals. We found that the parasitoi ds' activity and abundance was well correlated with the activity and a bundance of their host, and that all four parasitoid species covaried in concert with one another. In fact, the magnitude of correlation bet ween the different species in this system was greater than the correla tion with temperature. This shows clearly that an entirely exotic comm unity, reassembled piecemeal as a result of biocontrol efforts, can en d up with patterns of temporal covariation that are highly coincident. One other interesting result concerns the speed with which sprayed tr ees were recolonized by the fruit fly and its parasitoids. The time th at it took each species to reach its mean density prior to removal by the first pyrethrin spray at 0600 hours varied. It took 2 h for female B. dorsalis to recolonize guava trees to pre-spray levels. It took 3 h for Bi. arisanus, 4 h for D. longicaudata, 7 h for Bi. vandenboschi and 14 h for P. incisi to reach pre-spray levels. The fact that Bi. ar isanus recolonized vacant trees almost as rapidly as did the fruit fly pest suggest that there is little opportunity for the fruit fly to es cape in space and time by ''staying one step ahead of its enemies''.