Better explicating the strengths and shortcomings of these models will help refine projections and improve transparency in the years ahead.
Image credit: Witsawat.S.
Edited by James H. Brown, University of New Mexico, Albuquerque, NM, and approved September 25, 2008 (received for review May 9, 2008)
Abstract
Sodium is an essential nutrient whose deposition in rainfall decreases with distance inland. The herbivores and microbial decomposers that feed on sodium-poor vegetation should be particularly constrained along gradients of decreasing sodium. We studied the use of sucrose and NaCl baits in 17 New World ant communities located 4–2757 km inland. Sodium use was higher in genera and subfamilies characterized as omnivores/herbivores compared with those classified as carnivores and was lower in communities embedded in forest litter than in those embedded in abundant vegetation. Sodium use was increased in ant communities further inland, as was preference for the baits with the highest sodium concentration. Sucrose use, a measure of ant activity, peaked in communities 10–100 km inland. We suggest that the geography of ant activity is shaped by sodium toxicity near the shore and by sodium deficit farther inland. Given the importance of ants in terrestrial ecosystems, changing patterns of rainfall with global change may ramify through inland food webs.
Footnotes
- 1To whom correspondence should be addressed. E-mail: mkaspari{at}ou.edu
Author contributions: M.K., S.P.Y., and R.D. designed research; M.K., S.P.Y., and R.D. performed research; M.K. analyzed data; and M.K. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
- © 2008 by The National Academy of Sciences of the USA
On the biogeography of salt limitation: A study of ant communities
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