Leafminers, Early Leaf Abscission, and Parasitoids: A Tritrophic Interaction

Publisher: John Wiley & Sons Inc

E-ISSN: 1939-9170|70|5|1219-1226

ISSN: 0012-9658

Source: Ecology, Vol.70, Iss.5, 1989-10, pp. : 1219-1226

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Abstract

We investigated the interplay of the native holly leafminer, Phytomyza ilicicola, and leaf abscission by the American holly, Ilex opaca, an evergreen understory tree which is extensively planted as an ornamental. We carried out our study at both an urban and a forest site in northern Delaware. Leaf abscission rates increased in response to mining by Phytomyza. However, early abscission either did not affect or increased miner survivorship. This result differs from several previous studies in which leaf abscission has been found to decreased herbivore survivorship. One reason for lack of a negative effect was that leaves were not dropped until miners had pupated in the leaf. The other reason is reduced parasitism; since parasitoids did not search fallen leaves, abscission actually decreased mortality due to these natural enemies. Overall, our results indicate that the timing of leaf abscission in relation to the life cycle of herbivorous insects, and in relation to natural enemy attack, will determine how abscission influences herbivore demography.