Unsociable juvenile male three-spined sticklebacks grow more attractive
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.
Why do animals vary in personality, and how is such variation maintained within a population? An interesting approach for understanding this is studying how personality traits are correlated with other fitness-related traits within the pace-of-life framework. For the first time, our results show the link between sociability at the juvenile stage and the expression of sexual ornament during reproduction in male three-spined sticklebacks. Sociable juveniles may benefit from reduced predation risk, but they grow less attractive and this may reduce their mating success during reproduction. Thus, the trade-off between survival and reproduction may contribute to the maintenance of among-individual variation in behavior.
KeywordsAnimal personality Carotenoid Fecundity Pace-of-life Sexual signal Shoaling
We thank three anonymous reviewers for constructive comments and J. Dominguez, A. Gonzalez, and J. Díaz for help during the study.
Compliance with ethical standards
Wild fish were sampled under permission from the Xunta de Galicia (021/2013), and the experiment was approved by the Animal Ethics Committee of the University of Vigo (17/2012 and 10/2014).
Funding was provided by the Spanish Ministerio de Economía y Competitividad (CGL2012-40229-C02-02 and CGL2014-60291-JIN) and the Xunta de Galicia (2012/305).
Conflict of interest
The authors declare that they have no competing interests.
- Bakker TCM (1994) Evolution of aggressive behaviour in the threespine stickleback. In: Bell MA, Foster SA (eds) The evolutionary biology of the threespine stickleback. Oxford University Press, Oxford, pp 345–380Google Scholar
- Krause J, Ruxton GD (2002) Living in groups. Oxford University Press, OxfordGoogle Scholar