Comparative studies of mortality in the wild are necessary to understand the evolution of aging; yet, ectothermic tetrapods are underrepresented in this comparative landscape, despite their suitability for testing evolutionary hypotheses. We present a study of aging rates and longevity across wild tetrapod ectotherms, using data from 107 populations (77 species) of nonavian reptiles and amphibians. We test hypotheses of how thermoregulatory mode, environmental temperature, protective phenotypes, and pace of life history contribute to demographic aging. Controlling for phylogeny and body size, ectotherms display a higher diversity of aging rates compared with endotherms and include phylogenetically widespread evidence of negligible aging. Protective phenotypes and life-history strategies further explain macroevolutionary patterns of aging. Analyzing ectothermic tetrapods in a comparative context enhances our understanding of the evolution of aging.

The Orsini's viper (Vipera ursinii) is one of the most threatened snakes in Europe due to its highly fragmented distribution and specific open environment (steppic habitat) requirement. French populations are isolated on top of mountain massifs of the southern Prealps/Alps. Mitochondrial sequences (cytochrome b) and 6 microsatellite loci have been used to estimate the levels of genetic diversity and isolation within and among 11 French fragmented populations (a total of 157 individuals). Eleven cytochrome b haplotypes with a limited divergence were observed (mean divergence between haplotypes: 0.31%). However, we detected considerable genetic differentiation among populations (global F(ST) = 0.76 and 0.26 for mitochondrial and nuclear DNA, respectively). Results indicate that 3 populations possibly went through a bottleneck and 1 population showed low genetic diversity compared with the others. Although a significant isolation by distance was detected for both markers, strong differentiation was also observed between geographically close populations, probably due to the ragged landscape that constitutes a serious barrier to gene flow owing to the limited dispersal capability of the viper. Despite some discrepancies between the 2 markers, 8 Management Units have been identified and should be considered for future management projects.

1. While it has long been known that species have contrasted life expectancy (pace of mortality) and generation time (pace of reproduction), recent studies have also uncovered that the shape of adult age trajectories of mortality and reproduction can vary remarkably among species along a continuum of senescence ranging from strong deterioration (senescence), insignificant deterioration (negligible senescence) to improvement with advancing age (negative senescence). 2. As for many long-lived ectotherms with asymptotic growth and increasing reproductive output with age, snakes are good candidates for negligible senescence to occur. Yet, intraspecific variation in the pace and shape of actuarial and reproductive senescence across wild populations of these species remains to be explored. 3. Here, we used 37 years of mark-recapture data in two nearby habitats inside a meadow viper Vipera ursinii population to quantify life expectancies, generation times and the shape of actuarial and reproductive senescence. 4. Female vipers maintained stable reproductive performances at old ages, even when accounting for the predicted increase of fertility with body size, providing evidence for negligible reproductive senescence in both habitats. 5. Males had a higher adult mortality and a shorter life expectancy on average than females and actuarial senescence shifted from negligible senescence in the optimal habitat to strong senescence in the sub-optimal habitat. 6. Overall, these results demonstrate that micro-geographic environmental variation can generate qualitative shifts in actuarial senescence patterns. This highlights that taking into account the within-species plasticity of age-dependent trajectories could prove useful in better understanding what determines the evolution of life-history age trajectories.