Do ant mosaics exist in pristine lowland rain forests?

Ant mosaics have been described as characteristic elements of arboreal ant communities from tropical plantations, and it is often assumed that they al so exist in undisturbed lowland rain forests. Until now, however, there hav e been no studies from pristine rain forests to show this. Our investigatio ns on the mechanisms structuring arboreal arthropod communities in a southe ast-Asian lowland rain forest allowed us to compare our results with the pr edictions of the ant mosaic theory. According to this theory aggressive dom inant ant species should maintain mutually exclusive territories. Furthermo re, communities of associated nesting species dominated by the same dominan t species should be more similar to each other than communities governed by other dominants. The ant communities of 19 individuals of three understore y tree species were collected with an improved method of canopy fogging tha t guaranteed selective tree sampling in a multilayered rain forest. Ten tre es were re-fogged after 6 months and seven again after 3 years to investiga te whether the reorganization of the ant communities occurred in a similar way. To test whether the pattern of an ant mosaic emerged when not only sin gle trees but also somewhat larger areas containing several adjacent trees were sampled, we collected the nesting ant species from a group of Aporusa lagenocarpa with tuna baits. All ant communities were highly heterogeneous in their species composition and neither negative nor positive species asso ciations were found. The lack of an ant mosaic in mature forests is also su ggested by a Monte Carlo computer simulation, according to which ant commun ity composition differed only slightly from random. The re-fogged communiti es showed the same structural heterogeneity as was found in the first fogge d communities, without any observable convergence to the original species c omposition. No pioneer or climax species could be identified. All results c ombined indicate that the ant mosaic theory does not apply to the mature lo wland rain forest investigated, where community organization seems to be th e product of very complex dynamic processes.