Spiders bring new insight into the eco-evolutionary drivers of body size variation and sexual size dimorphism in arthropods

Abstract

Body size has been used thoroughly in arthropod ecology as a reliable trait to assess fitness responses to changes in environmental factors. Among these, spiders represent a large and diverse group, colonizing almost all terrestrial habitats. Here, we propose a review on intraspecific body size variation in arthropods over two main macroecological spatial gradients--latitude and elevation--both of high interest in a global warming context. We found that more species with a direct than with an indirect development present a converse Bergmann cline along both gradients. Focusing on spiders, we propose that life history traits such as voltinism, mobility, and brood care influence intraspecific body size patterns--potentially hiding large-scale patterns. Further, we assessed interspecific sexual size dimorphism (SSD) in spider species. We found that extreme SSD--the most original feature in spider biometry--is influenced by hunting guild rather than phylogeny of spider families, suggesting that ecological factors prevail over evolutionary drivers in shaping SSD.