Ants, elevation, phylogenetic diversity and community structure

Abstract

Testing the degree of support for macroecological patterns requires that the data behind these hypotheses be available for examination and re-testing. Using geographically wide-spread incidence matrices and a multi-gene phylogeny for ants (Hymenoptera: Formicidae), I calculated phylogenetic measurements of alpha and beta diversity and elevation to test the degree of support for the expected relationships between diversity and elevation (negative) and between phylogenetic clustering and elevation (positive). Whether diversity was estimated morphologically or phylogenetically, the elevational decay of alpha diversity was more frequently a linear decline than a mid-elevation peak. However the expectation that phylogenetic community structure would more likely be clustered with increasing elevation was not supported. This might be due to the fact that the physiological limitations filtering the taxa present are expressed at the species level and are thus beyond the resolution of this phylogeny. Trends linking elevational decay in beta diversity to temperature and precipitation were weak, but the results do support Janzen's 1967 prediction that communities on tropical mountains were less similar to each other than in temperate mountain communities. At the genus level, these data suggest that there is no general pattern regarding whether environmental/habitat filters (clustering) or inter-specific competition (dispersion) filter the taxa present. Instead, this analysis suggests that the community assemblages are not significantly different from random across elevation or temperature. These findings reinforce how important it is to support intuition with data and how critical it is to make data public and accessible so that hypotheses can be re-examined and tested.