Digest: Colony size drives the evolution of reproductive specialization in ants

Using data from 546 ant species, Turner et al. (2026) address why some ant workers retain reproductive capacity while others evolve complete sterility. They show that increases in colony size consistently favour worker sterility and greater queen-worker size dimorphism. Across the phylogeny, reproductive specialization evolves gradually and has arisen repeatedly. This study causally links colony size to caste differentiation, strengthening the size-complexity hypothesis and clarifying how social groups transition toward greater biological integration.