Schaefer Scott A, Lauder George V
Department of Ichthyology, Academy of Natural Sciences, 1900 Ben Franklin Parkway, Philadelphia, Pennsylvania, 19103-1195.
Department of Ecology and Evolution, University of California, Irvine, California, 92717.
Evolution. 1996 Aug;50(4):1661-1675. doi: 10.1111/j.1558-5646.1996.tb03938.x.
The "decoupling hypothesis" has been proposed as a mechanistic basis for the evolution of novel structure and function. Decoupling derives from the release of functional constraints via loss of linkages and/or repetition of individual elements as redundant design components, followed by specialization of one or more elements. Examples of apomorphic decoupling have been suggested for several groups of organisms, however there have been few empirical tests of explicit statements concerning functional and morphological consequences of decoupling. Using the loricarioid catfishes, we tested one particular consequence of decoupling, the prediction that clades possessing decoupled systems having increased biomechanical complexity will exhibit greater morphological variability of associated structures than outgroups having no such decoupled systems. Morphometric procedures based on interlandmark distances were used to quantify morphological variance at three levels of design at successive nodes in the loricarioid cladogram. Additional landmark-based procedures were used to localize major patterns of shape change between clades. We report significantly greater within-group morphometric variance at all three morphological levels in those lineages associated with decoupling events, confirming our predictions under the decoupling hypothesis. Two of 12 comparisons, however, yielded significant variance effects where none were predicted. Localization of the major patterns of shape change suggests that disassociation between morphological and functional evolution may contribute to the lack of fit between variance predictions and decoupling in these two comparisons.
“解耦假说”已被提出作为新结构和功能进化的机制基础。解耦源于通过失去联系和/或将单个元素重复作为冗余设计组件来释放功能限制，随后一个或多个元素发生特化。已经针对几组生物体提出了适应性解耦的例子，然而，对于有关解耦的功能和形态学后果的明确陈述，几乎没有实证检验。我们以甲鲶科鲶鱼为研究对象，测试了解耦的一个特定后果，即预测拥有解耦系统且生物力学复杂性增加的进化枝，与其相关结构的形态变异性将比没有这种解耦系统的外类群更大。基于地标间距离的形态测量程序被用于量化甲鲶科系统发育树中连续节点上三个设计层次的形态方差。额外的基于地标的程序被用于定位进化枝之间形状变化的主要模式。我们报告称，在与解耦事件相关的那些谱系中，所有三个形态层次上的组内形态测量方差都显著更大，证实了我们在解耦假说下的预测。然而，在12项比较中有两项产生了显著的方差效应，而在这些比较中并没有预测到会出现这种效应。形状变化主要模式的定位表明，形态和功能进化之间的分离可能导致了这两项比较中方差预测和解耦之间的不匹配。
