Variations in life-history traits in the common frog Rana temporaria (Amphibia : Anura): a literature review and new data from the French Alps

Life-history traits of Rana temporaria were studied in an alpine French pop ulation and in the literature. In the living frogs, mean adult body length was greater in females than in males. Sexual dimorphism in body length was 0.109 using Lovich & Gibbons (1992) formula, but tended to decrease with ag e. Age of adult frogs was assessed by skeletochronology, and age distributi on was not significantly different between the sexes (range 4-15 years in m ales, 5-12 in females). Adult survival rate was about 0.80 in both sexes. O nce maturity was reached, the total expected longevity was 6.1 years in mal es and 5.5 years in females. Age and body length were positively correlated in both sexes. The growth coefficient (K) was 0.47 in males, and 0.55 in f emales, mainly reflected as faster female growth between metamorphosis and maturation. Growth rate generally decreased before sexual maturity was reac hed. On average, females matured 1 year later than males. Newly metamorphos ed froglets averaged 16.1 mm. When combined with published data from 12 Eur opean populations of R. temporaria, the following general patterns emerge. Mean adult body length is significantly greater in females than in males, a nd mean body length at maturity shows the same trend. Variation in mean age at maturity and in longevity are considerable among populations, but there is no consistent trend of difference between the sexes. Body length and ag e are correlated between males and females, i.e. populations with long and old males also have long and old females. Mean adult body length, mean body length at maturity, age at maturity, and longevity all increase with decre asing activity period. Adults exposed to a short activity period grow slowe r but attain a greater final length. Sexual dimorphism in body length gener ally increases as activity period gets shorter. Polygons describing norms o f reaction for maturation in an age-body length space are similarly oriente d in both sexes, but with a wider range in age for females. This is due to an older age at maturity for females in populations with a short activity s eason. Mean age and length at maturity are significantly correlated in fema les, but not in males, partly supporting the hypothesis that this species h as a flexible pattern of development. Observed patterns are compared with p redictions from life-history theory, paying attention to all life stages an d environmental variation.