Host Leaf Selection by Leaf Miners: Interactions among Three Trophic Levels

Abstract

The influence of leaf characteristics on host leaf selection and survivorship in an endophagous insect were studied in a leaf—mining species, Stilbosis juvantis. Dry mass measurements of mined and unmined leaves (after abscisson) showed that the leaf miner does not select leaves for oviposition and subsequent larval feeding based on leaf size, possibly because densities of S. juvantis are typically low and this miner consumes only a small part of a leaf. However, census of 18 host trees, on 6 of which the proportion of damaged leaves had been experimentally increased, revealed that these leaf miners do select significantly more intact leaves than damaged ones for ovisposition. S. juvantis on damaged leaves experienced significantly lower survivorship, owing to increased parasitism, than did miners on intact leaves. The higher rate of attack by parasitoids is probably attributable to physical or chemical alterations in damaged leaves. Thus, damaged to leaves by previous herbivores modifies leaf selection by miners. These results indicate a subtle interaction among species at three trophic levels in this plant—herbivore system. Indirect negative interactions occur between guilds (leaf chewers and leaf miners) via changes in rates of parasitism rather than through resource—based competition.