Temperature drives caste-specific morphological clines in ants

The morphology of organisms relates to most aspects of their life history and autecology. In particular, morphology can reflect adaptation to the abiotic environment in which species occur. As such, elucidating the drivers of morphological variation along environmental gradients might give insight into processes limiting species distributions. In eusocial organisms, the concept of morphology is more complex than in solitary organisms. Eusocial insects such as ants exhibit drastic morphological differences between reproductive and worker castes. How environmental selection operates on the morphology of each caste, and whether caste-specific selection has fitness consequences is largely unknown, but potentially crucial to understand what limits ant species’ distributions. Here, we used 26,472 georeferenced morphometric measurements from 2206 individual ants belonging to 32 closely related North American species in the genus Formica to assess how ant morphology relates to geographic variat...