Allen’s rule is an ecogeographical pattern whereby the size of appendages of animals increases relative to body size in warmer climates in order to facilitate heat exchange and thermoregulation. Allen’s rule predicts that one consequence of a warming climate would be an increase in the relative size of appendages, and evidence from other bird species suggests that this might be occurring. Using measurements from museum specimens, we determined whether spatio-temporal variation in bills and legs of Australian Pachycephalidae species exhibits within-species trends consistent with Allen’s rule and increases in temperature attributable to climatic warming. We conducted regression model analyses relating appendage size to spatio-temporal variables, while controlling for body size. The relative bill size in four of the eight species was negatively associated with latitude. Tarsus length showed no significant trends consistent with Allen’s rule. No significant increases in appendage size were found over time. Although bill size in some species was positively correlated with warmer temperatures, the evidence was not substantial enough to suggest a morphological response to climatic warming. This study suggests that climate change is not currently driving adaptive change towards larger appendages in these species. We suggest that other adaptive mechanisms might be taking place.

中文翻译：

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澳大利亚吹口哨和伯劳鹅口疮的形态时空变化：气候变化是否会引起较大的附肢？

艾伦的法则是一种生态地理模式，在温暖的气候下，动物附肢的大小相对于身体大小会增加，以便促进热交换和温度调节。艾伦法则预测，气候变暖的后果之一是附属物的相对大小增加，其他鸟类的证据表明这可能正在发生。利用博物馆标本的测量，我们确定了澳大利亚Pachycephalidae物种的帐单和双腿的时空变化是否显示出符合Allen规则的物种内趋势以及气候变暖导致的温度升高。我们进行了回归模型分析，将附件大小与时空变量相关联，同时控制了身体大小。八个物种中四个物种的相对账单大小与纬度呈负相关。骨长度没有显示出符合艾伦法则的显着趋势。随着时间的推移，没有发现阑尾大小的明显增加。尽管某些物种的账单大小与温度升高呈正相关，但证据不足以表明对气候变暖的形态反应。这项研究表明，气候变化目前并未将适应性变化推向这些物种更大的附肢。我们建议可能正在发生其他自适应机制。证据不足以表明对气候变暖的形态反应。这项研究表明，气候变化目前并未将适应性变化推向这些物种更大的附肢。我们建议可能正在发生其他自适应机制。证据不足以表明对气候变暖的形态反应。这项研究表明，气候变化目前并未将适应性变化推向这些物种更大的附肢。我们建议可能正在发生其他自适应机制。