Morphological Strategies in Ant Communities along Elevational Gradients in Three Mountain Ranges

Abstract

Species traits often vary in a coordinated manner, making up an ecological strategy comprised of suites of interrelated traits. Environmental gradients, such as those along elevational gradients, provide an ideal venue in which to examine variation in ecological strategies with the environment. We examined variation in the morphological strategies of ants along elevational gradients on thirteen mountains across three mountain ranges in central and south-eastern Australia. We pitfall-trapped ants, counted and identified workers and measured morphological traits. Most species showed a hump-shaped relationship between occurrence and elevation, and several responded to microhabitat variables. Morphological traits varied along two key axes: “gracility”, where high values indicated longer-legged species with dorsally positioned eyes and smooth, bare cuticles; and “size and darkness”, where species with high values were larger and darker. Analysis of assemblage-weighted means revealed that gracility decreased with temperature and increased with precipitation, suggesting links with desiccation tolerance. Size and darkness increased with UV-B, declined with increasing canopy cover and peaked at mid-temperatures. We thus detected strong shifts in dominant morphological strategies along our elevational gradients. However, the multifunctionality and interrelatedness of traits and the covariance of climatic factors may make isolation of the function of individual traits difficult. Further, the predictive power of our models may be limited in the context of novel environments predicted under global change.