ANT DIVERSITY AND ABUNDANCE ALONG AN ELEVATIONAL GRADIENT IN THE PHILIPPINES

Ant communities were surveyed along an elevational gradient in the Phi lippines extending from lowland dipterocarp forest (250 m elevation) t o messy forest (1750 m). Standardized pitfall trapping in arboreal and terrestrial microhabitats at seven sites yielded 51 species. Collecti ng by hand at five of the sites yielded 48 species. The two methods pr oduced substantially different assemblages, with only 22 species (29%) taken in common. Only a fraction of the total ant community appeared to be sampled at most of the sites. Measures of species richness and r elative abundance peaked at mid-elevations and declined sharply with i ncreasing elevation. Ants were extremely rare above 1500 m elevation. Arboreal ants were trapped much less frequently than terrestrial ants at all sites. Ant species that were abundant had broader elevational d istributions than those chat were less common, but most species were r are and occurred at only one or two sites. The elevational patterns fo r ants are largely the inverse of those documented for Philippine smal l mammals which reach their greatest diversity and abundance at high e levations where ants are rare. This suggests that the two groups may i nteract competitively. Some of the patterns observed or inferred from this study may apply to tropical ant communities in general, and are p resented as series of testable hypotheses as a guide and stimulus for future research.