Ants as indicators of exposure to environmental stressors in North American desert grasslands

TitleAnts as indicators of exposure to environmental stressors in North American desert grasslands
Publication TypeJournal Article
Year of Publication1999
AuthorsWhitford WG, Van Zee J, Nash M.S., Smith W.E., Herrick JE
JournalEnvironmental Monitoring and Assessment
Date Published1999
ARIS Log Number096095
Keywordsenvironmental stressors, exposure indicators

The relative abundance of ant species was measured by pit-fall trapping at 44 sites in southern New Mexico and southeastern Arizona, U.S.A.. 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 abundance of species, and species richness were the same on disturbed and undistrubed 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 similaar but differed from the assemblages in exotic salt cedar and native ash riparian woodlands. Ant species exhibited remarkable resistance to human-induced disturbance 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 ants 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.