PARENT SESSION
Oral Session # 41: Herbivory III: Forests and Soils.
Presiding: R Jones
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 103.

Leaf ties as oviposition sites for forest arthropods.

Lill, John^{*,1, 2}, Marquis, Robert², ¹ George Washington University, Washington, DC, USA² University of Missouri-St. Louis, St. Louis, MO, USA

ABSTRACT- Most efforts to explain variation in the local structure of insect herbivore communities have focused on plant quality factors (e.g., nutritional and secondary chemistry), given their demonstrated impacts on components of herbivore fitness. However, for many, if not most insects, host plants also provide a "home" for their resident herbivores, sheltering them from the elements and attack from natural enemies. We experimentally investigated the influence of leaf shelters made by leaf-tying caterpillars on colonization via oviposition for forest arthropods of white oak (Quercus alba). We created artificial leaf ties by clipping together adjacent leaf pairs and compared oviposition rates on these leaves with non-tied leaf pairs on the same plant. Because naturally occurring leaf ties typically contain leaf-tying caterpillars, frass, silk, and leaf damage, we also investigated the effects of these occupancy-related cues on oviposition by comparing oviposition in initially occupied vs. unoccupied leaf ties. Compared to non-tied controls, oviposition (across all taxa) was four times greater on unoccupied clipped leaves and five times greater on previously occupied ties. These results indicate that pre-existing shelters are actively sought out by adults, and that occupancy-related cues further enhance the level of oviposition. The magnitude of the effect varied considerably among feeding guilds, with leaf-chewing herbivores and scavengers showing the strongest response and sucking insects and predators showing less of response. Moreover, caterpillar species differed in their response to occupancy-related cues. Our results highlight the importance of herbivore-herbivore interactions in shaping natural arthropod communities. Our previously published experimental work demonstrated that plant architecture influences the level of leaf-tying in this system. Therefore, the impact that these herbivore-herbivore interactions have on the local arthropod communities depends in part on plant architecture.

Key words: Quercus alba, herbivore community, leaf tie, arthropod