The pace-of-life syndrome (POLS) hypothesis predicts variation in behaviour and physiology among individuals to be associated with variation in life history. Thus, individuals on the “fast” end of POLS continuum grow faster, exhibit higher metabolism, are more risk prone, but die earlier than ones on the “slow” end. Empirical support is nevertheless mixed and modelling studies suggested POLS to vary along selection gradients. Therefore, including ecological variation when testing POLS is vastly needed to determine whether POLS is a fixed construct or the result of specific selection processes. Here, we tested POLS predictions between and within two fish populations originating from different ecological conditions. We observed opposing life histories between populations, characterized by differential investments into growth, fecundity, and functional morphology under identical laboratory conditions. A slower life history was, on average, associated with boldness (latency to emergence from a refuge), high activity (short freezing time and long distance travelled), and increased standard metabolism. Correlation structures among POLS traits were not consistent between populations, with the expression of POLS observed in the slow-growing but not in the fast-growing population. Our results suggest that POLS traits can evolve independently from one another and that their coevolution depends upon specific ecological processes.
Behavioural ecology research increasingly focuses on why genetic behavioural variation can persist despite selection. Evolutionary theory predicts that directional selection leads to evolutionary change while depleting standing genetic variation. Nevertheless, evolutionary stasis may occur for traits involved in social interactions. This requires tight negative genetic correlations between direct genetic effects (DGEs) of an individual’s genes on its own phenotype and the indirect genetic effects (IGEs) it has on conspecifics, as this could diminish the amount of genetic variation available to selection to act upon. We tested this prediction using a pedigreed laboratory population of Mediterranean field crickets (Gryllus bimaculatus), in which both exploratory tendency and aggression are heritable. We found that genotypes predisposed to be aggressive (due to DGEs) strongly decreased aggressiveness in opponents (due to IGEs). As a consequence, the variance in total breeding values was reduced to almost zero, implying that IGEs indeed greatly contribute to the occurrence of evolutionary stasis. IGEs were further associated with genetic variation in a non-social behaviour: explorative genotypes elicited most aggression in opponents. These key findings imply that IGEs indeed represent an important overlooked mechanism that can impact evolutionary dynamics of traits under selection.
ACKNOWLEDGMENTS
16We thank Yvonne Cämmerer and Bettina Rinjes for help in maintaining the crickets, In animal contests, individuals respond plastically to the phenotypes of the opponents 28 that they confront. These 'opponent' -or 'indirect' -effects are often repeatable, e.g., 29 certain opponents consistently elicit more or less aggressiveness in others.
TITLEBehavioural mediators of genetic life-history trade-offs: a test of the pace-of-life syndrome hypothesis in field crickets AUTHORS Santostafano, F; Wilson, A J; Niemala, PT; et al.
JOURNAL
Proceedings of the Royal Society B: Biological Sciences
DEPOSITED IN ORE
February 2018This version available at http://hdl.handle.net/10871/31632
COPYRIGHT AND REUSEOpen Research Exeter makes this work available in accordance with publisher policies.
A NOTE ON VERSIONSThe version presented here may differ from the published version. If citing, you are advised to consult the published version for pagination, volume/issue and date of publication
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