Elasticity and selection on life-history traits in a complex life cycle organism, the common Frog Rana temporaria (Amphibia : Anura)

Organisms living at low altitudes or latitudes can be active and grow almos t all year round whereas the growing season is truncated in higher latitude s and altitudes. In numerous ectotherms, growth slows down or stops at sexu al maturity, and age and size at this main transition change in different d irections when the environment (biotic and/or abiotic) influences growth. A s age and size are components of the phenotype which can influence fitness, their study concerns life-history evolution. Hypothesis about these variat ions are idealy tested among populations of the same species, and we presen t here a literature synthesis on life history variation, and more precisely on age, size and growth in the common Frog (Rana temporaria) from differen t European populations. Males and females exhibit similar trends when confr onted with the reduction of activity period (both with altitude and latitud e) : age at maturity is delayed and body size increases. With published dat a on tills species and other anuran species, we describe characteristics of the whole life cycle in relation to environmental gradients. Focusing on g enetic versus environmental determinism, we propose an evolutionary scenari o to explain phenotypic variations of life-history traits observed in Rana temporaria, among environmental gradients.