Stress tolerance in some Chacoan dolichoderine ants: implications for community organization and distribution

Stress-tolerance strategies in ants have been little studied in the context of ant communities. To examine this relationship, the behaviour and activity patterns of several dolichoderine ants,Forelius nigriventrisForel andDorymyrmex exsanguisForel and allies, with other members of a species-rich, scavenging ant assemblage in two habitats in the Argentine Chaco was studied. Both groups of dolichoderines were more active in the overgrazed-desertified habitat than in the forested habitat.Forelius nigriventriswas relatively thermophilic, andD. exsanguisand allies were active over a broad range of environmental conditions and were tolerant of cold conditions. These dolichoderines were subordinate in aggressive interactions with other species at baits, and were abundant at baits only when other species were absent. Competitive interactions may have led to stress tolerance in these ants. Stress tolerance on a local scale may also permit the geographic distribution of these ants (particularlyD. exsanguis) into zones of relatively harsh climate.