Caterpillars in at least 24 families of Lepidoptera function as ecosystem engineers by tying leaves together with silk to make shelters. These leaf-ties have been shown to provide a wide range of benefits for their inhabitants including decreased temperature, increased humidity, decreased toxic effects of foliage consumption, and protection from a variety of predators. Leaf-ties have been shown to strongly affect arthropod abundance, species richness, and community structure at the whole tree level. However, these studies were done over short periods so only provide a snapshot of the leaf-tie community. This study assayed the inhabitants of leaf-ties over ten weeks on ten trees each of American beech, Fagus grandifolia, and white oak, Quercus alba. Fifty-five leaf-ties were created on each tree using metal hair clips by clipping two adjacent leaves together to create an area of overlap on June 11 2009. Five ties were haphazardly harvested each week for ten weeks beginning June 23 2009. Caterpillars were identified to species as larvae when possible; unknown larvae were reared and identified as adults. All non-lepidopteran arthropods were identified to Recognizable Taxonomic Units (RTU's).
Results/Conclusions
Over the ten weeks sampled, a total of 909 and 1624 arthropods colonized ties on American beech trees and white oak trees, respectively, for a total of 2533 arthropods. The arthropod communities inhabiting these leaf-ties differed markedly in composition despite the fact that the two tree species are closely related and intermingled in the same forest. There were 78 RTU's found on American beech and 91 RTU's on white oak, but only 15 RTU's were shared between both. On American beech colonist abundance peaked in early August, while species richness remained relatively constant across the season. In contrast, both occupancy and species richness on white oak showed bi-modal peaks in late July and early August. The lepidopteran inhabitants were fairly similar except that the most common inhabitant on white oak, Psilocorsis quercicella, never colonized beech. There were also seasonal differences in when species colonized the two tree species. For example, Tortricids (Lepidoptera) colonized white oak only early in the season while they colonized beech throughout the season. This survey provides a unique analysis of leaf-tie inhabitants that illustrates the phonological changes in species composition as well as clearly displaying how closely related tree species can contain vastly different arthropod communities.
