Geographical distribution of color phenotypes and associations with ecological predictors remains poorly understood. An important geographic pattern concerning this topic is Gloger's rule, which predicts the increase of pigmentation in endothermic animals from cold and dry to warm and wet environments. Didelphid marsupials exhibit a variety of color patterns, ranging from light and dark uniform to more complex colorations. However, surprisingly little is known about the adaptive significance of dark coloration in this singular group of mammals. Using a phylogenetic comparative approach, we investigated whether coloration in different body regions of didelphids (i.e., dorsum and face) is associated with variables representing heat and humidity of the environment, as predicted by Gloger's rule. We demonstrated that Gloger's rule explains the interspecific color variation in American marsupials, especially when considering the facial region. Thus, dark coloration was more frequent among didelphid species occupying warm and wet environments than cold and dry environments. We also discuss the selective forces that can potentially explain coat color variation in didelphid marsupials, including camouflage, pathogen resistance, and pleiotropy hypotheses.

中文翻译：

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着色的阴暗面：生态地理证据支持格洛杰在美国有袋动物中的统治

颜色表型的地理分布以及与生态预测因子的关联仍然知之甚少。与该主题相关的一个重要地理模式是 Gloger 规则，它预测吸热动物从寒冷干燥到温暖潮湿环境的色素沉着增加。Didelphid 有袋动物表现出多种颜色图案，从浅色和深色均匀到更复杂的颜色。然而，令人惊讶的是，对于这种奇异的哺乳动物群体中深色的适应性意义知之甚少。使用系统发育比较方法，我们调查了双海豚不同身体区域（即背部和面部）的着色是否与代表环境温度和湿度的变量相关，正如格洛杰规则所预测的那样。我们证明了 Gloger' s 规则解释了美国有袋动物的种间颜色变化，尤其是在考虑面部区域时。因此，与寒冷和干燥环境相比，在温暖和潮湿环境中的双海豚物种中深色更常见。我们还讨论了可能解释双海豚有袋动物毛色变化的选择性力量，包括伪装、病原体抗性和多效性假设。