Assembly of a twig-nesting ant community: disturbance as a window to non-neutral processes

Several factors influence assembly of twig-nesting ants in shaded coffee agroecosystems. Twig-nesting ants are nest-site limited and inhabit similar sized nests, thus competition and colonization processes are likely important. I examined effects of a large-scale disturbance on twig-nesting ants with time since disturbance. During June of 2007 and 2008, farmers pruned trees in two areas within a 45-ha plot, and left another area uncut. I sampled ants during July 2008, forming a treatment gradient of time since disturbance (uncut, cut one year ago [c1], cut one month ago [c2]). I sampled ants on coffee bushes in 2-3 hectares per treatment. Then, I compared occupation rate, species richness, and relative abundance of ants. I encountered 19 species of ants from 534 nests. Nest availability did not differ with treatment, but more nest sites were occupied in c2 (82.9%) than in c1 (70.7%) and even fewer were occupied in uncut (57.7%). Ant richness was highest in c2 (16 species), lower in c1 (13) and lowest in uncut (11). Species relative abundance differed by treatment. Relative abundance of the two most common species did not differ with treatment. Four species only occurred in c2, and four species occurred only in either c1 or c2. Relative abundance of two species declined while abundance of two other species increased with time since disturbance. Differences in occupation, richness, and relative abundance indicate disturbance influences community assembly in human-managed habitats. Further, directional changes of species composition signal that non-random processes may drive assembly in undisturbed sites.