The spatial and temporal patterns of oviposition-resource use of various Anastrepha spp. fruit flies within the canopies of individual fruit trees were determined over periods of 4–6 yr in the state of Veracruz, Mexico. The flies examined were Anastrepha obliqua (Macquart), Anastrepha striata Schiner, Anastrepha fracterculus (Wiedemann), and Anastrepha alveata Stone, and their respective hosts were Spondias mombin L. (Anacardiaceae), Psidium guajava L., Psidium sartorianum (Berg.) Ndzu (Myrtacaea), and Ximenia americana L. (Olacaceae). The canopies were divided into six sectors: three strata (vertical planes of low, middle, and high canopy) and an exterior and interior component of the various heights. All ripe fruits produced by each tree species were individually harvested, weighed, and maintained until all larvae had exited and pupated. Because of the commonly positive correlation between fruit size and infestation, fly distributions were described using a novel technique, two-level hierarchal regression analysis, as deviations from the expected numbers of insects in a sector given the distributions of fruit weights within the canopy. Overall, there was a tendency for A. alveata to be more abundant in the lower portions of the tree, for A. striata to be more abundant in the upper, for A. obliqua to be less abundant in the upper, and for A. fraterculus to be uniformly distributed. The yearly densities of A. striata and A. fraterculus within the P. guajava tree were negatively correlated, and this seems to be due to annual changes in environment rather than to exploitive competition for oviposition resources. Along an altitudinal gradient (0–1,800 m), A. striata was more abundant than A. fraterculus at sea level and relatively less abundant at altitudes of 1000 m and higher. We suggest that habitat characteristics (oviposition-resource availability and quality, and microclimatic variables), intraspecific competition, and the behaviors of natural enemies and frugivores are potentially important interactive factors that influence the distribution of resource use to a different extent in each of the tephritid species.
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Vol. 97 • No. 3