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Review Article

Territoriality in ants (Hymenoptera: Formicidae): a review

Adams, E.S.

Abstract: Territory defense by ants is a social process with strong ecological effects. I review the mechanisms by which ants partition space, the behaviors governing individual and colony territorial responses, and the effects of territory defense on populations and communities. Partitioning of space is sometimes accomplished by massive battles, but well defined boundaries are also maintained by less violent means, including avoidance of competitors. Ants flexibly adjust individual and group territorial behavior according to location, scent marks, prior experience, and the local density of nestmates and competitors. An ongoing theoretical challenge is to incorporate these processes into models that accurately predict division of space. Many studies have documented strong effects of territorial interactions on the growth, movement, survival, reproduction, and spacing of competing colonies. Far fewer studies have measured the net effect of territoriality on population dynamics. Fighting can be costly, but there is little evidence that it appreciably reduces worker density or that loss of territoriality promotes the invasiveness of exotic ants. Territorial ants are said to be at the top of competitive hierarchies that structure ant communities. Because much of the evidence is based on correlations, some claims about the community effects of territoriality have met with skepticism. Nonetheless, there is strong evidence from diverse habitats that territory defense produces multi-species mosaics of exclusive foraging areas and that territorial dominants influence the occurrence of some other ant species.