The Ecology of Hawaiian Flower-Breeding Drosophilids. 2. Adult Dispersions and Reproductive Ecology

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Abstract
Hawaiian flower-breeding drosophilids (Scaptomyza calinginos) and their host morning glories (Ipomoea acuminata) were examined in Hawaii Volcanoes National Park, Kilauea, Hawaii. The daily dispersions of adults among fresh blossoms showed that males tend to overdisperse, whereas females tend to aggregate. The densities of adults per blossom were higher in sunlit blossoms than in shaded blossoms, but female reproductive effort (eggs per female per blossom) was higher. Variation in female reproductive effort did not correlate with variation in either temperature or humidity in the field. Instead, observations and experimental evidence indicate that male courtship behavior has an inhibitory effect on oviposition within crowed blossoms. This finding may represent a density-dependent component in the maintenance of the low fecundity of this species.