Altitudinal variation in body size in the Rice Frog (Rana limnocharis) in southwestern China

Bergmann’s rule states that, within species of endotherms, individuals tend to be larger in cooler environments, and has been reputed to apply to some ectotherms including amphibians. However, the validity of the rule has been debated, questioning whether Bergmann’s clines are generally present in anurans. In the view, we studied altitudinal variation in body size in the rice frog (Rana limnocharis) among populations from Sichuan province located at three altitudes to find if there exist any differences in a relatively small altitudinal range (290-375 m). The results showed that individuals from higher altitudes tended to be larger in body size than lower altitudes, which was consistent with Bergmann’s cline. Moreover, when the effect of age was removed, variation in body size of the frogs across altitudes still remained. Our findings suggested that age affected the pattern of variation in body size across the altitudinal cline, we also discussed that factors other than age also contributed to size differences among populations.