ECOLOGY OF TWIG-DWELLING ANTS IN A WET LOWLAND TROPICAL FOREST

Ants of tropical wet forests are common, yet practically unstudied, de spite their importance in nutrient cycling and seed bank dynamics. I i nvestigated the ecology of a leaf litter assemblage of twig-dwelling a nts in lowland tropical wet forest and contrasted it with the better k nown ecologies of ground- and tree-dwelling ants. Nest densities at La Selva, Costa Rica were high (7.48 nests/m2) and potential nest sites were abundant. Colonies moved frequently (residence times for species ranged from 35 to 146 days) from one twig nest to another, occupying a wide range of twig types. Experiments with artificial nests showed th at colonization was not reduced by the presence of resident ant coloni es. Queenright nests (in which at least one queen is present) and quee nless workers, as well as dealate queens, colonized artificial nests. Activity times and diet composition did not differ between the two spe cies with largest sample sizes; workers were active under most conditi ons. Despite their abundance, twig-dwelling ants are apparently limite d neither by availability of nest sites nor food. Many of the 32 speci es found coexisting at La Selva may be limited by high mortality durin g alate dispersal or colony movement.