sources for P. fortis is unknown, but its occupation pattern suggests that honeydew-

producing coccoids may not be a primary source of nutrition. Work in other systems has

shown complex relationships among ants, myrmecophytes and ant-tended Hemiptera

(Gaume et al. 1998, Lapola et al. 2005), but the importance of these interactions in most

systems is unknown.

 The presence of a large, polydomous colony of the habitat generalist Cr. carinata

in one of the plots apparently reduced the colonization frequency of Aztecapittieri in 1-

yr-old plants and completely prevented colonies of that otherwise dominant species from

occurring in 5-yr-old trees. The dominance of Cr. carinata in this plot could be

attributable to a number of factors, but certainly this species' mode of colonizing the 1-

yr-old trees (colony expansion from the leaf litter) allowed it to exploit the empty

domatia prior to discovery by foundress queens ofA. pittieri. Crematogaster carinata

displayed a markedly different occupation strategy than A. pittieri on older plants as well,

in which the former species left significantly more domatia uninhabited on 5-yr-old trees

where it was the numerically dominant species (Fig. 3a). It appeared that the competitive

interactions between the two dominant ants resulted in available habitat (uncolonized

domatia) that Ce. setulifer was able to occupy and then successfully defend against the

numerically dominant colonies ofA. pittieri and Cr. carinata.

 Interaction with natural enemies can alter the outcome of competitive interactions,

thereby promoting coexistence (Worthen 1989, Pacala and Crawley 1992, Tokeshi 1999,

Chesson 2000). The high mortality of A. pittieri queens due to attacks by the parasitoid

wasp, C. affinis, may have mediated the success of founding queens of other species. In

his description of this genus, Brues (1922) stated that a congener wasp, C. aztecicida, was