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United States Department of Agriculture

Agricultural Research Service

Title: ANTS AS INDICATORS OF EXPOSURE TO ENVIRONMENTAL STRESSORS IN NORTH AMERICANDESERT GRASSLANDS

Authors
item Whitford, Walter
item Van Zee, Justin
item Nash, Maliha - USEPA
item Smith, Walter - NEW MEXICO STATE UNIV
item Herrick, Jeffrey

Submitted to: Environmental Monitoring and Assessment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 1997
Publication Date: N/A

Interpretive Summary: We studied various descriptors of ant communities in 44 sites in southern New Mexico and southern Arizona. Ants were trapped using pit-fall traps, and the sites chosen were disturbed or non-disturbed, had varying levels of exposure to grazing by livestock, were dominated by a non-native species, or had been subjected to changes due to efforts to restore degraded rangelands. We did not find the expected patterns of ant distributions. Ant communities, therefore, show remarkable resistance to human-induced disturbances in many rangeland areas. Rangeland dominated by Lehmans lovegrass, a grass species introduced from South Africa, had fewer large seed harvesting ants but this was the only difference we found. We concluded that ants cannot be used as indicators of rangeland exposure to stress.

Technical Abstract: The relative abundance of ant species was measured by pit-fall trapping at 44 sites in southern New Mexico and southeastern Arizona, USA. Sites were selected for study based on documentation of a history of disturbance or protection from disturbance, exposure to varying intensities of livestock grazing, dominance by an exotic species of plant and vegetation change resulting from disturbance or restoration efforts. Ant community composition, relative abundances of species, and species richness were the same on disturbed and undisturbed sites. None of the metrics based on hypothesized responses of ants to disturbance clearly distinguished between disturbed and undisturbed sites. Ant communities on sites where restoration efforts have resulted in distinct differences in vegetative cover and composition were similar to the ant communities on degraded unrehabilitated sites on the same soil type. Ant communities in riparian cottonwood gallery forests in Arizona and New Mexico were similar but differed from the assemblages in exotic salt cedar and native ash riparian woodlands. Ant species exhibited remarkable resistance to human-induced disturbances in these rangeland areas. In grasslands dominated by the South African grass, Eragrostis lehmanniana Nees, large seed harvesting ants, Pogonomyrmex spp., were greatly reduced in abundance compared to native grasslands. Other ant metrics were not different in E. lehmanniana grasslands and native grasslands. We conclude that ants cannot be used as indicators of exposure to stress, ecosystem health or of rehabilitation success on rangeland ecosystems. Ants are also not useful indicators of faunal biodiversity in rangeland ecosystems.

Last Modified: 10/1/2014
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