Body size predicts ant worker longevity: a hierarchical analysis of field and laboratory survival across phylogenetic lineages.

Abstract

Lifespan is a key life-history trait that shapes ecological strategies and colony fitness in social insects, yet its drivers remain unclear. We evaluated whether intrinsic traits-especially worker body size, a principal pace-of-life axis and phylogeny-predict survival across 18 ant species from five subfamilies monitored in the field and in captivity. Mark-recapture data analysed with hierarchical models accounting for imperfect detection showed that larger workers lived longer in both environments, highlighting intrinsic physiological properties as the strongest determinant of longevity. Worker lifespans ranged from 23 to 394 days, and field and laboratory survival were positively correlated. Body mass scaled negatively with colony size: small colonies invested in large, long-lived workers, whereas large colonies relied on smaller, short-lived workers. In captivity, survival was modestly higher for some clades and comparable for others, indicating mixed laboratory-field differences consistent with hazard reduction in certain lineages; Dolichoderinae and Myrmicinae showed little to no improvement. Phylogenetic signal was weak, indicating that lineage imposes little constraint beyond body size. These results confirm body size as a strong-and phylogeny as a weak-predictor of worker longevity. Laboratory assays capture relative field lifespans despite environmental complexity, based on the first comparative survival dataset for a local ant assemblage spanning multiple lineages.