Ants are prominent members of most arid ecosystems. Although the ubiquity, abundance, and diversity of ants in arid environments suggests that they have great potential to serve as bioindicators, several features of their ecology suggest that ants may be less responsive to environmental change than other animal taxa within arid environments. For example, ants residing in arid climates most often nest underground, a trait that may potentially buffer them from aboveground changes in environmental conditions. Sociality may also confer the ability to resist environmental change. Worker polymorphism and the ability to regulate colony size and caste ratios may enable ants to track changing resource supplies more efficiently than other animal taxa. I evaluated the potential of ants to serve as bioindicators in an arid region in northern Mexico by examining the response of ant assemblages to severe habitat disturbance in this region.

Results/Conclusions

I examined changes in the abundance and diversity of ants in response to the conversion of native desertscrub and thornscrub habitats to exotic grass pastures in the southern reaches of the Sonoran Desert of northern Mexico. In addition, I assigned species to functional groups based on taxonomic and ecological criteria and examined the response of functional group composition to land conversion. Over 44,000 individual ants and 4,500 species occurrences were recorded across all study sites. Ant assemblages exhibited remarkable resiliency to land conversion. Land conversion reduced ant abundance, but only marginally lowered ant diversity. Beta-diversity among ant assemblages was similar in both exotic grass pastures and native habitats. The functional group composition of exotic grass pastures was similar to that of native habitats. The lack of a clear and consistent response of ant abundance and diversity to severe habitat modification suggests that ants may not be well-suited to serve as bioindicators in this arid environment.