Unsociable juvenile male three-spined sticklebacks grow more attractive

摘要

An animal's personality may be an adaptive behavioral response of individuals to consistent differences in physiology and life-history. Studying the relationship between behavior and other fitness-related traits within the pace-of-life syndrome (POLS) framework, which explains the integration of different traits using the concept of a fast-slow life-history continuum, may thus be a useful approach to understanding the evolution and maintenance of animal personality. According to the POLS hypothesis, for example, fast individuals should be behaviorally more active, bolder or less sociable, and potentially invest more in reproduction than slow individuals. Here, we examined whether the sociability of juvenile sticklebacks (Gasterosteus aculeatus) is linked with their key reproductive traits, carotenoid-based nuptial coloration of males and egg production of females. We also tested whether experimental manipulation of environmental conditions (control vs. warm winter) can change pace-of-life and the link between behavioral and reproductive traits. Male sticklebacks prone to shoaling expressed lower peak red coloration at the reproductive stage, during which they were solitary and territorial. In females, fecundity was not correlated with early social behavior. Experimental sticklebacks reared in warm winter conditions decreased their investment in reproduction, but the negative relationship between sociability and sexual signal of males was maintained. Our results suggest that the POLS could partly explain the maintenance of personality under predation pressure or severe mating competition. In natural environments, any benefit to sociable male sticklebacks may be counterbalanced by the cost of growing less attractive.