Zhang, Y.; Zhang, Y.; Hao, C.

Trade-offs, negative associations among life history traits, are fundamental to understanding life history evolution. While traditional studies have focused mainly on pairwise trait relationships, organisms allocate finite energy across multiple processes simultaneously, necessitating a multivariate perspective. Here, by integrating both bivariate and multivariate phylogenetic frameworks, we investigated the complex relationships among six key life history traits (adult body size, offspring size, development time, adult lifespan, clutch size, and clutch frequency) across species of mammals, birds, reptiles, and insects. We demonstrated that multivariate frameworks significantly alter inferred trait relationships across species. For instance, a direct relationship between offspring size and adult lifespan becomes indirect when additional traits are considered. Moreover, while some multivariate patterns are consistent across taxa, others are taxon-specific. Our findings suggest that life history variations emerge from the interplay of multiple traits, emphasizing the need to view life history evolution through the lens of interconnected ecological and evolutionary processes.