Developmental Modules & Evolvability: The Gastropod Foregut as a Model

为什么有些生物群自首次出现以来就发生了爆炸性的多样化，而另一些生物群却在数百万年的时间里毫无变化？这个谜团是进化发育生物学这个新兴领域的核心问题，它不满意传统的观点，即自然选择作用于后代之间随机的、基因指定的变异，提供了物种进化的完整故事。虽然选择显然很重要，进化发育生物学家强调，信息从基因型到表型的转移是通过发育过程发生的，发育组织可以影响作为选择原材料的变异的数量和种类。普遍的假设认为，在被组织成半自主模块的发育系统中，最大程度的“可进化性”将被发现，这些模块可以在不破坏整个复杂结构的发育完整性的情况下衍生出不同的表型。这一假设在概念上很有吸引力，但其有效性取决于找到能够证明高进化率与模块化发展组织之间存在联系的系统。

Why have some groups of organisms diversified explosively since their first appearance, while others have puttered along for millions of years without much change at all? This mystery is a core issue for the emerging field of Evolutionary Developmental Biology, which is dissatisfied with the traditional view that natural selection acting on random, genetically-specified variation among offspring provides the complete story about how species evolve. Although selection is clearly important, evolutionary developmental biologists emphasize that transfer of information from genotype to phenotype occurs via the process of development and developmental organization can influence the amount and kind of variation produced as raw material for selection. The prevailing hypothesis suggests that the greatest amount of ‘evolvability’ will be found among developmental systems organized into semi-autonomous modules that can spin off variant phenotypes without disrupting the developmental integrity of whole complex structures. This hypothesis is conceptually appealing but its validity depends on finding systems in which a link between high rates of evolution and a modular organization of development can be demonstrated.