Altitudinal variation in body size in Bufo minshanicus supports Bergmann’s rule

Abstract

According to Bergmann’s rule, in endothermic species, body sizes of individuals tend to be larger in colder climates compared to those in warmer climates. Some ectotherms, including amphibians, have also been found to conform to this rule. However, the validity of this rule is disputed, as it is uncertain whether Bergmann’s clines are generally applicable to all anuran species. Here we studied altitudinal variation in mean body size, egg size, age, and growth rate in Bufo minshanicus across six altitudes in the eastern Tibetan Plateau. Our results showed that mean body size increased with increasing altitude, which is consistent with Bergmann’s rule. Toads from higher altitudes also tended to have faster growth rates and older mean ages of reproductively mature adults, but did not have larger egg sizes. We suggest that, as growth rate is positively correlated with altitude, and it contributes to body size variation more than mean age does, then this explains why this species follows Bergmann’s rule.