What factors set species' range edges? One general hypothesis, often attributed to Darwin and MacArthur, is that interspecific competition prevents species from inhabiting the warmest portions along geographic gradients (i.e., low latitudes or low elevations). A prediction arising from this Darwin–MacArthur hypothesis is that lower elevation species are better competitors than related higher elevation species. An alternative prediction is that higher elevation animal taxa will tend to be better competitors because they will tend to be larger (Bergmann's rule). Here, I test these opposing predictions.

中文翻译：

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海拔较低的动物没有比海拔较高的动物更好的竞争者。

哪些因素设置了物种的范围边缘？一种普遍的假设（通常归因于达尔文和麦克阿瑟）是种间竞争阻止物种沿地理梯度（即低纬度或低海拔）居住在最温暖的部分。对此达尔文-麦克阿瑟假说的预测是，与相关的高海拔物种相比，低海拔物种是更好的竞争者。另一种预测是，海拔较高的动物分类单元将趋向于成为更好的竞争者，因为它们趋向于更大（Bergmann法则）。在这里，我测试了这些相反的预测。