Ecological, Morphological, and Behavioral Determinants of Lepidoptera Parasitism across a Latitudinal Gradient

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Parasitoids may have significant effects on community processes as natural enemies of herbivorous insects, especially Lepidoptera. Previous studies of Lepidoptera-parasitoid associations have revealed strong effects of host ecology, morphology, and behavior on parasitism rates, but it has been difficult to compare results between studies conducted in different ecological communities. We compared patterns of parasitism of exophytic caterpillars from three communities to examine how the determinants of caterpillar parasitism rates vary along a latitudinal gradient. Over 170 species of caterpillars were collected from mesquite-oak savanna in Southeastern Arizona, scored for behavioral, morphological, and ecological attributes, and reared to pupation. Patterns of parasitism relative to these host traits were compared to results from similar studies in Costa Rica and the Northeastern U.S. Several effects of caterpillar characteristics on parasitism were consistent across sites, but depended on the type of parasitoid. Across all sites, few defenses were effective in limiting parasitism by flies. Wasp parasitism was limited by behavioral defenses such as thrashing across all sites, and was higher on concealed, gregarious hosts. Host morphology affected susceptibility to parasitism by wasps and flies in opposite ways, suggesting that competition between parasitoid taxa may influence host use. A previously uncovered trend towards higher parasitism rates of hosts that are protected from predators was upheld, however this enemy free space may be more important for tropical parasitoids than for temperate species.

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