Developmental Modules & Evolvability: The Gastropod Foregut as a Model

为什么有些生物群体从第一次出现起就发生了爆炸性的变化，而另一些生物群体却沿着了数百万年，没有发生太大的变化？这个谜团是新兴的进化发育生物学领域的核心问题，它不满意传统观点，即自然选择作用于后代中随机的遗传特异性变异，提供了物种如何进化的完整故事。虽然选择显然是重要的，进化发育生物学家强调，信息从基因型到表型的转移发生在发育过程中，发育组织可以影响作为选择原材料产生的变异的数量和种类。流行的假说认为，最大量的“进化性”将被发现在发展系统组织成半自主模块，可以剥离出不同的表型，而不破坏整个复杂结构的发展完整性。这一假说在概念上很有吸引力，但其有效性取决于找到一个系统，在该系统中，可以证明高进化率和发展的模块化组织之间的联系。

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.