Epiphytic Associations with Ants

Abstract

Ants are the most common arboreal insects of tropical forests (Leston 1973; Erwin 1983; Wilson 1987) and possibly the most frequent animal contacts of epiphytic plants. It is not surprising, then, that epiphytes share a number of ecological interactions with ants, and that some of these interactions have become prominent features of epiphyte biology. Not only are ants abundant and ubiquitous, but their unique social attributes proffer a functional significance disproportionate to numbers. As eusocial insects (Wilson 1971), ants exhibit a division of colony labors between reproductive and sterile (worker) castes. Primary responsibility for more dangerous, extranidal activity resides with the workers, and the colony as a reproductive unit often enjoys considerable immunity from predation (Wilson 1971; Jeanne and Davidson 1984). Consequently, ant populations are often limited by food and/or nest sites (e.g. Wilson 1959; Leston 1973; Swain 1977; Brown and Davidson 1977) and are likely to be responsive over both ecological and evolutionary time to the provisioning of such resources by epiphytes and other plants. Relatively long life expectancies allow many ants to divert considerable energy and resources early in the life history to modifications of the nesting and foraging environments (Forel 1929). In turn, these modifications may further counteract negative abiotic and biotic selection pressures and further prolong colony lifespans.