Habitat degradation increases stress-hormone levels during the breeding season, and decreases survival and reproduction in adult common lizards
The allostatic load model describes how individuals maintain homeostasis in challenging environment and posits that costs induced by a chronic perturbation (i.e., allostatic load) are correlated to the secretion of glucocorticoids, such as corticosterone. Habitat perturbations from anthropogenic activities are multiple and functional responses to those are still unclear. Here, we manipulated the habitat quality in 24 semi-natural populations of the common lizard during 1 year. We tested the predictions of the allostatic load model that habitat degradation should increase baseline corticosterone levels, and should induce concomitant physiological changes, such as lipid mobilization and lower immunocompetence, and demographic changes, such as lower body growth, survival and/or reproductive performances. Our results highlight stage-dependent effects of habitat degradation on physiological traits during the breeding season: adult lizards had higher baseline corticosterone levels and yearling lizards had a lower inflammatory response than adults, whereas juveniles had higher circulating lipid levels than yearlings and adults without concomitant change in corticosterone levels. In addition, habitat degradation reduced the performances of adults but not of juveniles: in low habitat quality populations, adult males had a lower survival and females had a smaller fecundity. These results are in accordance with the allostatic load model given that allostatic load was detected only during the season and in life stages of maximal energy expenditure. This underlines the importance to account for individual energy requirements to better understand demographic responses to habitat perturbation.
KeywordsAllostasis Corticosterone Fitness Immunocompetence Triglycerides
We are thankful to students and staff at the CEREEP, especially Samuel Perret and Beatriz Decencière, for assistance in the field and laboratory. This study was funded by the CNRS, the Agence Nationale de la Recherche (ANR-13-JSV7-0011-01 to S.M.) and the Région Île-de-France R2DS program (grant 2013-08 to S.M., J.F.L.G. and R.J.). Protocols were done under the agreement with the Regional ethics committee in animal experiment No3 of the Région Île-de-France. The authors declare that they have no conflict of interest.
Author contribution statement
RJ, SM, and JFLG conceived and designed this study, performed statistical analyses and wrote the manuscript. RJ, SM, JFLG, AD, and SA performed the experiment. RJ, AD, and CH provided biochemical analyses.
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