Body sizes in endothermic species tend to increase as temperature decreases in accordance with Bergmann’s rule. However, why do some species support Bergmann’s clines while others reverse it? This question should be solved by considering the relative contributions of mean age and growth rate on adult ectotherm body size. Here we studied altitudinal variation in mean body size, age, and growth rate in Rana kukunoris through 16 sites at different altitudes in the eastern Tibetan Plateau. Our results revealed that mean body size decreased as altitude increased in each sex, which fails to obey Bergmann’s rule, but supports the converse Bergmann’s rule. Frogs at lower altitudes tended to grow faster than individuals of the same species at higher altitudes. Conversely, age of adults did not significantly increase as altitude increased. Therefore, we suggest that lower growth rate limits the mean individual body size at the altitudes, explaining why this species follows the converse Bergmann’s rule. The effect of age cannot be ignored because decreasing body length with increasing altitudes is not significant when removing the effect of age.

根据伯格曼定律，吸热物种的体型往往会随着温度的降低而增加。然而，为什么有些物种支持伯格曼氏族，而另一些则相反？这个问题应该通过考虑平均年龄和生长速度对成年等温体大小的相对贡献来解决。在这里，我们研究了Rana kukunoris平均体型、年龄和生长速率的高度变化穿越青藏高原东部不同海拔的16个地点。我们的结果表明，随着海拔的升高，每个性别的平均体型减小，这不符合伯格曼规则，但支持相反的伯格曼规则。低海拔的青蛙往往比高海拔的同一物种的个体生长得更快。相反，随着海拔的升高，成年人的年龄并没有显着增加。因此，我们建议较低的生长速率限制了海拔高度的个体平均体型，解释了为什么该物种遵循逆伯格曼规则。年龄的影响不容忽视，因为在消除年龄影响时，随着海拔的升高而减少体长并不显着。