The Tropical Ant Mosaic in a Primary Bornean Rain Forest

In primary lowland rain forest in Brunei Darussalam, we studied arboreal ant communities to evaluate whether densities and spacing of spatially territorial taxa along 2.9 km of well-studied trails are consistent with existence of a continuous mosaic of dominant ants. A median intercolony distance of 24.5 m, about twice or less distances over which colonies of most included species regularly ranged, suggested a relatively continuous mosaic. Despite relying on nesting sites in preformed plant cavities, carpenter ants contributed > 70 percent of mapped colonies. Most belonged to the Camponotus ( Colobopsis ) cylindricus (COCY) complex, including SE Asia's 'exploding' ants. Their lack of aggression against certain Polyrhachis species was associated with interspecific territory sharing by members of the two groups, and with a dominance-discovery trade-off. Experimental approaches yielded evidence for two putative contributors to positive association. Larger-bodied Polyrhachis parasitize food-finding abilities of smaller, more populous Camponotus workers, and the two taxa cooperate in territorial defense. Highly territorial and predatory weaver ants ( Oecophylla smaragdina ) were an important component of the ant mosaic in primary forest, second only to codominant COCY and Polyrhachis taxa. Members of the genus Crematogaster were significantly associated with Oecophylla in baiting censuses and regularly monopolized near-nest baits to the exclusion of weaver ants. Litter ant abundances differed between territories of Oecophylla and less predatory COCY species, but direction of difference was inconsistent over time. The densely packed mosaic of spatially territorial, and differentially predatory, taxa in Bornean rain forest likely contributes to spatial variation in ant effects on plant and arthropod communities.