North American Seed-harvester Ants

■ Abstract Seed-harvester ants are a dominant and conspicuous insect group throughout arid portions of the southwestern United States and northern Mexico, and they include ∼75 species. Intense study in the late 1970s and early 1980s led to the paradigm that interspecific competition for limited seed resources is the primary factor that structures seed-harvester ant communities. This review attempts to adjust this paradigm, suggesting that interspecific competition for food is probably less important than previously thought, whereas intraspecific competition is common and strong. Abiotic-habitat factors also have important effects on local species composition and attributes. This review also emphasizes several aspects of seed-harvester ants that have been poorly studied, including historical factors, adaptive radiation, and biogeography, to provide a more detailed evolutionary background for understanding existing species assemblages.