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Harvard Forest Symposium Abstract 2005

  • Title: Changes in Ant Community Structure and Composition Associated with Hemlock Decline in New England
  • Primary Author: Aaron Ellison (Harvard University)
  • Additional Authors: Jonathan Chen (Oberlin College); David Diaz (Harvard University); Chelsea Kammerer-Burnham (Clark University); Matthew Lau (Humboldt State University)
  • Abstract:

    Impacts of invasive species on the structure of the invaded communities is an active area of ecological research, but the effects of the hemlock woolly adelgid (HWA) on forest organisms other than economically important timber trees rarely have been examined. To date, studies of HWA impacts principally have assessed mortality rates of hemlock and their subsequent replacement by early-successional hardwoods, and changes in core ecosystem properties. However, if certain taxa are restricted to hemlock forests, or if dominance by hemlock precludes the colonization or occurrence of particular species, then removal of hemlock could result in changes in overall species diversity and composition within HWA-infested stands and across the landscape. We examined this hypothesis for forest ant communities in southern New England. Specifically, we asked how ant species richness and composition differed among intact hemlock stands, HWA-infested and damaged stands, and mid-successional hardwood “controls”. In total, 22 species of ants were collected from 16 sites spread across Connecticut and Massachusetts. Average species richness among sites ranged from 3 to 12 (mean = 7), and was inversely related to the percent of hemlock basal area in the stand. Average dissimilarity among sites was 73%; notably, Formica spp. were virtually absent from intact, uninfested hemlock stands. At the stand level, loss of hemlock due to HWA results in an increase in ant species diversity, but this local increase in diversity is offset by homogenization of diversity across the landscape. The rate and impacts of colonization by Formica spp. into HWA-infested stands may alter ecosystem structure and dynamics in these forests and merits further study.

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