This ongoing work examines the relationships between the functional traits of ant species and the diversity and dynamics of North American ant assemblages. In the 1990’s, we used standardized methods to sample 49 ant assemblages across North America. We are currently resampling the same locations using the same methods, recording ant species diversity, nest density and activity-density at LTER and NEON sites across the continental USA. Thus we are comparing assemblage diversity and structure across a 20 year window. In the resampling, we also measured critical thermal limits (maxima and minima) and estimated trophic level (using N & C isotopic signatures) of ant workers of the most common species at each site to test the hypothesis that changes in species abundance and assemblage structure are driven by differences in functional traits amongst species.
While the project is not completed, here we compare the preliminary results from elevational gradients at 4 different LTER network sites (Coweeta, Niwot Ridge, Sevilleta and H.J. Andrews). While there is some species turnover, total species richness and nest densities remain remarkably similar across the 20 year window, thus there is little evidence of change in the elevational diversity gradient. Thermal trait space is phylogenetically autocorrelated and correlated with species diversity but becomes saturated at lower elevations.