Résumé
We studied a population of the alpine newt, Triturus alpestris, living at the upper limit of its altitudinal range (2200 m in the northwestern Alps) during the aquatic activity period. Age was estimated by skeletochronology applied to phalanges and body size was measured. Age structures were similar between sexes, with age at maturity at 9-11 years and longevity up to 20 years. Annual survival was 0.81. Females were significantly larger than males. Growth, modelled according to van Bertalanffy's growth model, was higher in females during the juvenile period. A comparative analysis of age and size at maturity, mean size, and longevity in several European populations distributed from sea level to high altitudes shows a significant increase in these phenotypic variables with the decrease of the duration of the activity period. The growth coefficient K, indicating the shape of the curve, is smaller in highland than in lowland populations, and the asymptotic size is smaller in the plain than at higher altitude. If adult size increases with altitude, age at maturity is extensively delayed in short activity period environments. The discussion is focussed on the patterns of variation of these traits. However, age and size of newts can also depend on traits of the previous stages of the life cycle, and we review several characteristics of the egg and larval stages in response to environmental gradients.