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

Abstract

Life-history traits of Rana temporaria were studied in an alpine French population 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 & Gibbon  s (1992) formula, but tended to decrease with age. Age of adult frogs was assessed by skeletochronology, and age distribution was not signi®cantly different between the sexes (range 4±15 years in males, 5±12 in females). Adult survival rate was about 0.80 in both sexes. Once maturity was reached, the total expected longevity was 6.1 years in males and 5.5 years in females. Age and body length were positively correlated in both sexes. The growth coef®cient (K) was 0.47 in males, and 0.55 in females, mainly re¯ected as faster female growth between metamorphosis and maturation. Growth rate generally decreased before sexual maturity was reached. On average, females matured 1 year later than males. Newly metamorphosed froglets averaged 16.1 mm. When combined with published data from 12 European populations of R. temporaria, the following general patterns emerge. Mean adult body length is signi®cantly greater in females than in males, and 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 age 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 decreasing activity period. Adults exposed to a short activity period grow slower but attain a greater ®nal length. Sexual dimorphism in body length generally increases as activity period gets shorter. Polygons describing norms of reaction for maturation in an age±body length space are similarly oriented 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 season. Mean age and length at maturity are signi®cantly correlated in females, but not in males, partly supporting the hypothesis that this species has a¯exible pattern of development. Observed patterns are compared with predictions from life-history theory, paying attention to all life stages and environmental variation.

Ageing and growth of the endangered midwife toad Alytes muletensis

“…on basic demographical parameters such as maximum and mean longevity, growth curves, growth rates and age at maturity in wild populations of Alytes muletensis. As in several amphibians, our data showed a positive correlation between body size (SVL) and age (Miaud et al 1999, Yilmaz et al 2005, Ma & Lu 2009). We observed differences in mean longevity between sexes, biased to older females, whilst the maximum longevity was similar between the sexes.…”

Differences in spawning date between populations of common frog reveal local adaptation

“…Dividing the covariance by the temperature variance component defines a regression slope for each random effect (20). In all cases, the slopes between temperature and first spawning date were negative: 150-km slope (21) and R. temporaria requires 2 or 3 years to reach sexual maturity (22). Therefore, terms involving year reflect plastic responses to temperature and are not significantly different from each other (pooled mean = −2.98, HPD: −4.84 to −1.33).…”

The genetic contribution to sex determination and number of sex chromosomes vary among populations of common frogs (Rana temporaria)

“…Postglacial colonization of northern-boreal regions by common frogs occurred very lately (o10 kya; Palo et al, 2004). Generation time under harsh climates can be estimated to 8 years (assuming age at first reproduction to be 4 years and annual survival rate 80%; Miaud et al, 1999), possibly more because fecundity increases with age. Hence, given the short timeframe since postglacial colonization (in the order of 1000 generations) and its seemingly localized distribution, this neo-sex chromosome system might be the youngest one described so far.…”