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Native riparian habitats cover a small percentage of the landscape in most arid lands. Irrigation, however, artificially expands these in some regions. It is important to understand whether human-modified landscapes can support species native to natural ecosystems. We examined butterfly communities in relatively undisturbed (nonagricultural) versus artificially created (agricultural) riparian habitats in the Walker River Basin in the western Great Basin (Nevada and California, USA). Habitat type did not significantly affect species richness. Butterfly abundance was greater, and evenness lower, in agricultural than in nonagricultural sites. Annual variability significantly affected species richness, total abundance, and evenness. The few species largely restricted to agricultural sites were geographically widespread and characteristic of disturbed habitats. Several relatively uncommon species were not present in agricultural sites. Riparian habitats created to support agriculture may help support some native butterfly species, but cannot substitute for undisturbed riparian habitats. (C) 1999 Elsevier Science Ltd. All rights reserved.