Effects of early nutritional stress on physiology, life histories and their trade-offs in a model ectothermic vertebrate.

Abstract

Early-life experiences can have far-reaching consequences for phenotypes into adulthood. The effect of early-life experiences on fitness, particularly under adverse conditions, is mediated by resource allocation to particular life-history traits. Reptiles exhibit great variation in life histories (e.g. indeterminate growth), thus selective pressures often mitigate the effects of early-life stress, particularly on growth and maturation. We examined the effects of early-life food restriction on growth, adult body size, physiology and reproduction in the checkered garter snake. Animals were placed on one of two early-life diet treatments: normal diet (approximating ad libitum feeding) or low diet (restricted to 20% of body mass in food weekly). At 15 weeks of age, low-diet animals were switched to the normal-diet treatment. Individuals fed a restricted diet showed reduced growth rates, depressed immunocompetence and a heightened glucocorticoid response. Once food restriction was lifted, animals experiencing nutritional stress early in life (low diet) caught up with the normal-diet group by increasing their growth, and were able to recover from the negative effects of nutritional stress on immune function and physiology. Growth restriction and the subsequent allocation of resources into increasing growth rates, however, had a negative effect on fitness. Mating success was reduced in low-diet males, while low-diet females gave birth to smaller offspring. In addition, although not a direct goal of our study, we found a sex-specific effect of early-life nutritional stress on median age of survival. Our study demonstrates both immediate and long-term effects of nutritional stress on physiology and growth, reproduction, and trade-offs among them.