Patterns and drivers of leaf-litter ant diversity along a tropical elevational gradient in Mexico

<p><b>Aim: </b>Given their high environmental variation over relatively short distances, mountains represent ideal systems for evaluating potential factors shaping diversity gradients. Despite a long-standing interest in ecological gradients, ant diversity patterns and their related mechanisms occurring on mountains are still not well understood. Here, we (i) describe species diversity patterns (α and β) of leaf-litter ants along the eastern slope of Cofre de Perote in Veracruz, Mexico, and (ii) evaluate climatic and spatial factors in determining these patterns.</p> <p><b>Location: </b>Veracruz, Mexico</p> <p><b>Taxon: </b>Leaf-litter ants</p> <p><b>Methods: </b>We sampled 320 m² of leaf litter spread across 8 equally-spaced sites from sea level to 3500 m of elevation. We used regression models to predict α-diversity patterns with climatic (temperature and precipitation) and spatial (geometric constraints) variables. We also assessed, through multiple regression based on distance matrices (MRM), the relative importance of habitat filtering and dispersal limitations for shaping total dissimilarity (βsor), turnover (βsim) or nestedness (βnes).</p> <p><b>Results: </b>A hump-shaped pattern was observed in the α- diversity with a peak at 600-1000 meters above sea level. This pattern is best explained by the temperature gradient with around 80% of variance explanation. β-diversity showed a non-linear pattern along the elevational gradient with total dissimilarity and turnover components better explained by habitat filtering (i.e., temperature distances).</p> <p><b>Main conclusions:</b> The importance of temperature on both α- and β-diversity patterns reinforces its widespread importance in shaping litter ant diversity patterns across elevational gradients. The hump-shaped pattern in species richness is probably the result of harsh abiotic conditions at the base and the top of the mountain combined with biotic attrition in lowland sites. Niche specialization of ant species in their optimal thermal zones may explain total dissimilarity and ant species replacement along the studied gradient. Taken all together, these results suggest a high relevance of temperature-driven mechanisms in the origin and maintenance of the biodiversity of ectothermic taxa.</p>