Monday, December 11, 2006

Guild dynamics of arthropods associated with eastern hemlock, Tsuga canadensis (L.) in the southern Appalachians

Carla Dilling, carla@dilling.net1, P. L. Lambdin, plambdin@utk.edu1, J. F. Grant, jgrant@utk.edu1, S. Buck1, R. Reardon2, and Rusty Rhea3. (1) University of Tennessee, Entomology and Plant Pathology, 2431 Joe Johnson Drive, 205 Ellington Plant Sciences Building, Knoxville, TN, (2) USDA Forest Service, Forest Health Technology Enterprise Team, 180 Canfield Street, Morgantown, WV, (3) USDA Forest Service, Forest Health Protection, 200 Weaver Boulevard, Asheville, NC

The primary objective of this project was to quantify community dynamics of the insect fauna on eastern hemlocks, Tsuga canadensis (L.), prior to the invasion by the hemlock woolly adelgid, Adelges tsugae Annand, to better understand the impact of invasive exotics on insect community structure. Tests were initiated to obtain and determine the guild dynamics among 300 insect species associated with eastern hemlock in the southern Appalachians. Phytophagous, predaceous, parasitoid, scavenger, fungivorous, and detrivorous guild assignments were made. The phytophagous insect guild was subdivided into chewers, sap suckers, flower feeders, pollen feeders, and seed feeders. Percent exotic and indigenous species within the various guild structures were determined. Exotic species represented 2% of the phytophagous guild and 4% of the predator guild. The competitive structure of the insect community was examined to assess guild structure using EcoSim. The mean c-score (.708) infers a community that is less competitive among guilds than expected by chance (mean c-score of simulated indices=.787 variance=.016). There was a significant association between guild on immature and mature hemlocks at low elevations but there is no association at high elevations. The number of species within the phytophagous guild was significantly higher on immature hemlocks, while species within the scavenger guild was significantly higher on mature hemlocks.