School of Biological and Conservation Sciences, University of KwaZulu-Natal, Scottsville, South Africa.
Biol Rev Camb Philos Soc. 2012 Feb;87(1):128-62. doi: 10.1111/j.1469-185X.2011.00188.x. Epub 2011 Jun 20.
The evolution of endothermy in birds and mammals was one of the most important events in the evolution of the vertebrates. Past tests of hypotheses on the evolution of endothermy in mammals have relied largely on analyses of the relationship between basal and maximum metabolic rate, and artificial selection experiments. I argue that components of existing hypotheses, as well as new hypotheses, can be tested using an alternative macrophysiological modeling approach by examining the development of endothermy during the Cenozoic. Recent mammals display a 10°C range in body temperature which is sufficiently large to identify the selective forces that have driven the development of endothermy from a plesiomorphic (ancestral) Cretaceous or Jurassic condition. A model is presented (the Plesiomorphic-Apomorphic Endothermy Model, PAE Model) which proposes that heterothermy, i.e. bouts of normothermy (constant body temperature) interspersed with adaptive heterothermy (e.g. daily torpor and/or hibernation), was the ancestral condition from which apomorphic (derived), rigid homeothermy evolved. All terrestrial mammal lineages are examined for existing data to test the model, as well as for missing data that could be used to test the model. With the exception of Scandentia and Dermoptera, about which little is known, all mammalian orders that include small-sized mammals (<500 g), have species which are heterothermic and display characteristics of endothermy which fall somewhere along a plesiomorphic-apomorphic continuum. Orders which do not have heterothermic representatives (Cetartiodactyla, Perissodactyla, Pholidota, and Lagomorpha) are comprised of medium- to large-sized mammals that have either lost the capacity for heterothermy, or in which heterothermy has yet to be measured. Mammalian heterothermy seems to be plesiomorphic and probably evolved once in the mammalian lineage. Several categories of endothermy are identified (protoendothermy, plesioendothermy, apoendothermy, basoendothermy, mesoendothermy, supraendothermy, and reversed mesoendothermy) to describe the evolution of endothermy during the Cenozoic. The PAE Model should facilitate the testing of hypotheses using a range of macrophysiological methods (e.g. the comparative method and the reconstruction of ancestral states).
鸟类和哺乳动物的温血进化是脊椎动物进化史上最重要的事件之一。过去对哺乳动物温血进化的假说的检验主要依赖于对基础代谢率和最大代谢率之间关系的分析，以及人工选择实验。我认为，现有的假说以及新的假说的组成部分，可以通过检查新生代温血的发展来使用替代的宏观生理学建模方法进行检验。最近的哺乳动物的体温范围为 10°C，这足以确定推动温血从原始（祖先）白垩纪或侏罗纪状态发展的选择压力。提出了一种模型（原始-衍生温血模型，PAE 模型），该模型提出，异温性，即正常体温（恒定体温）与适应性异温性（例如每日休眠和/或冬眠）之间的间隔，是从原始（祖先）衍生出刚性恒温的条件。检查了所有陆地哺乳动物谱系的现有数据以测试该模型，以及测试该模型的缺失数据。除了关于 Scandentia 和 Dermoptera 知之甚少之外，所有包含小型哺乳动物（<500 克）的哺乳动物目都有表现出异温性和表现出沿原始-衍生连续体的某种程度的温血特征的物种。没有异温性代表的目（鲸目、奇蹄目、鳞甲目和兔形目）由中等到大型哺乳动物组成，这些哺乳动物要么失去了异温性的能力，要么异温性尚未测量。哺乳动物的异温性似乎是原始的，并且可能在哺乳动物谱系中进化了一次。确定了几种类型的温血性（原始温血性、原始温血性、衍生温血性、基底温血性、中间温血性、超温血性和反转中间温血性）来描述新生代温血性的进化。PAE 模型应该使用各种宏观生理学方法（例如比较方法和祖先状态的重建）来促进假说的检验。
