Sex-specific aging: Sex differences in survival and health in a wild primate population

摘要: Ageing influences the functioning of most living organisms in myriad ways and has profound consequences for their reproductive fitness survival. Age-related changes an organism are thought to result from weakened selection against deleterious mutations acting after peak age, optimizing resource allocation reproduction versus self-maintenance. Consequently, life history theory predicts that rate senescence should be reduced age onset delayed with increasing lifespan. A high risk mortality extrinsic causes lead earlier or faster senescence. Extensions this prediction shorter-lived sex (e.g. males mammals) show Furthermore, sex-specific selective pressures lifespan might expected a preferential maintenance traits optimize immune function self-maintenance females, whereas male may better enhanced by prolonged investment competitive ability. Senescent declines thus trait- patterns. However, beyond comparative studies age-related rates, these predictions remain largely untested under natural conditions. The aim thesis was test elemental studying functional (within-individual deterioration physiological physical functioning) sexually monomorphic, small-bodied primate species (gray mouse lemur, Microcebus murinus) experiences its environment. To gain understanding prevalence across traits, how is influenced individuals poor condition, I examined trajectories four different components health together broadly indicate overall individual ability cope environmental demands: body mass, strength, gastrointestinal parasite burden allostatic load (baseline glucocorticoid level). estimate significance disappearance quantifying mass senescence, used long-term data (10-18 generations) captive breeding colony Brunoy, France, two wild populations Kirindy, western Madagascar. collected grip strength measurements fecal samples over dry rainy seasons monitored, individually marked gray lemur population. compare patterns between animals, additionally measured animals. In first study, declining found both, setting, senescent decline regain lost only captivity. Some evidence more condition-dependent females than males, intriguing reversal sex-bias detailed settings: live longer nature but outlive This study also confirmed female advantage despite sex-specific, seasonal fluctuation wild. In second no differences were hand indicator functioning, either setting. Contrary other invariably report stronger equally strong lemur. at old pronounced third estimated burdens (parasite morphospecies richness quantified via egg counts) as proxy predictions, declined similarly both sexes, possibly due acquired immunity impaired resistance parasites. initially experienced higher burden. The fourth motivated finding species, follows negative feedback regulation glucocorticoids, detrimental fitness. After validating assay quantify levels feces, tested aged animals would experience load. met season, perhaps indicating energetic demands coincide ecological season. summary, evidenced highly variable sex-, season-, setting-specific substantial aging measured. While observed some parameters, absence even others. Body best preserved until likely reflecting importance indicators survival associated strong, positive maintenance. theory, generally similar magnitude less relative females. implies early mortality, do not included health, “robust” phenotype required improved further including success, sexes confirm conclusion, results support fundamental population risk, sex. rapid, condition counteract act reduce prime age. fitness-enhancing differ sexes. Further investigation into multi-trait taxa can shed light on mechanisms determination animal kingdom, humans.