Canopy Vegetation Influences Ant (Hymenoptera: Formicidae) Communities in Headwater Stream Riparian Zones of Central Appalachia

In the eastern United States, eastern hemlock Tusga canadensis (L.) Carriere forests are threatened by the invasive hemlock woolly adelgid, Adelges tsugae, a pest that is causing widespread hemlock mortality. Eastern hemlock is an essential component of forested communities. Adelgid-induced hemlock mortality is causing a shift in forest composition and structure, altering ecosystem function and thereby influencing the arthropod community. Using pitfall traps at three sites, we monitored ground-dwelling arthropods at 30-d intervals in hemlock-dominated and deciduous-dominated forests in central Appalachia over 2 yr. Here, we focus on the ant community (Hymenoptera: Formicidae) collected in the summer months. Ants form a ubiquitous and integral component of the invertebrate community, functioning at various trophic levels as predators, herbivores, and omnivores, and fulfilling important roles in forest ecosystems. We found no difference in overall ant abundance between hemlock-dominated and deciduous-dominated forests but did detect significant differences in the genera Prenolepis between forest types (P < 0.01) and Aphaenogaster across study locations (P = 0.02). Three genera were unique to deciduous forests; one was unique to hemlock forests. Not surprisingly, total formicids and several genera demonstrated temporal differences in abundance, with greater numbers captured in July than in August. As hemlock woolly adelgid-induced mortality of eastern hemlock becomes more pervasive, changes in forest composition and structure are imminent, accompanied by shifts in hemlock associates.