Eco‐Evolutionary Drivers of Body Size Variation in Arthropods, With a Focus on Spiders

ABSTRACT Aim Body size has been used thoroughly in arthropod ecology as a reliable trait to assess fitness responses to changes in environmental factors. We aim to assess general patterns of intraspecific body size variation along macroecological gradients in arthropods. We more specifically discuss these patterns in spiders, as they represent a large and diverse group, colonising most terrestrial habitats. Location: Global. Time Period: 1982–2024. Major Taxa Studied: Arthropods. Methods We propose a systematic review and a meta‐analysis of 146 studies 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. Results We found that more species with direct than with indirect development present a converse Bergmann cline along both gradients. Main Conclusions We propose that life history traits such as voltinism, mobility and brood care influence intraspecific body size patterns—potentially hiding large‐scale patterns. This review gathers empirical data about body size variation along elevational and latitudinal gradients in arthropods, providing a step forward to a better understanding of the underlying mechanisms driving body size variation.