PS 17-27 - Experimental warming of entire assemblages alters foraging behavior in ants

Tuesday, August 9, 2011
Exhibit Hall 3, Austin Convention Center
Katharine L. Stuble, Ecology and Evolutionary Biology, University of Tennessee, David A. Fowler, Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, Robert Dunn, Biology, NCSU, Raleigh, NC and Nathan J. Sanders, The Natural History Museum of Denmark, The University of Copenhagen, København Ø

The composition of ecological communities has and will continue to change as a result of climate change, including increasing temperatures. However, the exact mechanisms driving these changes in community structure are often unclear. While shifts in the relative abundances of particular species may result from temperatures outside the thermal tolerances of those species, more subtle responses to temperature, including altered foraging behavior and modified interspecific interactions, may be important. Using a manipulative field experiment, we experimentally regulated air temperatures within 12 five-m diameter patches of an eastern deciduous forest at Duke Forest in North Carolina. Temperatures consistently ranged from ambient to 5.5 ºC above ambient. We examined the impacts of temperature on various metrics of foraging efficiency of ground-foraging ant species, including worker activity, food discovery ability, overall food acquisition, and the number of hours per day spent foraging by each species. We tested the hypothesis that warming shifts the relative ability of ant species to gather food resources, ultimately altering interspecific interactions, coexistence, and the structure of communities in the face of warming.


We found that temperature was related to the number of hours per day spent foraging as well as overall worker activity. However, responses were often contingent on species identity. For example, the number of hours per day that Crematogaster lineolata and Aphaenogaster rudis, two of the most abundant species in the assemblage, were found foraging on baits responded differently to warming. Foraging of C. lineolata increased by 167% in the hottest chambers (4.5˚C to 5.5˚C above ambient) relative to ambient chambers, while A. rudis decreased by 52% decrease in the hottest chambers. Likewise, the foraging activity (as measured by density of active foragers) of C. lineolata was 733% higher in the hottest chambers relative to ambient chambers, though foraging activity by A. rudis remained the same across temperature treatments. The effects of warming on resource collection were less clear, suggesting that warming my not influence actual food acquisition in intuitive ways. These data suggest that shifts in community composition that occur as a result of warming may, in part, be related to foraging behavior and competitive interactions rather than strict thermal tolerances.

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