Effects of tree mortality caused by a bark beetle outbreak on the ant community in the San Bernardino National Forest


Correspondence: Brian W. Spitzer, Department of Biology, University of Redlands, 1200 East Colton Ave., P.O. Box 3080, Redlands, CA 92373, U.S.A. E-mail: brian_spitzer@redlands.edu


  1. A severe bark beetle outbreak caused very high levels of tree mortality in the San Bernardino National Forest in southern California in 2003.
  2. In 2009, the impact of the outbreak on the ant community was examined by pitfall-trapping ants in 15 sites that saw high tree mortality (‘red’ sites) and 15 sites that suffered little or no tree mortality (‘green’ sites) during the outbreak.
  3. Ant species turnover between green and red sites was low, and no invasive species were observed.
  4. However, changes in the abundances of various species resulted in a significant alteration of the ant community.
  5. If the ant community is an accurate bioindicator of other taxa in this forest, the effects of the bark beetle outbreak may be described as dramatic but not catastrophic or irreversible.
  6. The changes in the ant community are consistent with the hypothesis that this community is structured by nest site limitation rather than inter-specific competition or thermal limitation.