Wray Gregory A
Department of Biology, Duke University, Durham, NC, United States.
Curr Top Dev Biol. 2022;146:79-112. doi: 10.1016/bs.ctdb.2021.10.004. Epub 2021 Dec 3.
As analyses of developmental mechanisms extend to ever more species, it becomes important to understand not just what is conserved or altered during evolution, but why. Closely related species that exhibit extreme phenotypic divergence can be uniquely informative in this regard. A case in point is the sea urchin genus Heliocidaris, which contains species that recently evolved a life history involving nonfeeding larvae following nearly half a billion years of prior evolution with feeding larvae. The resulting shift in selective regimes produced rapid and surprisingly extensive changes in developmental mechanisms that are otherwise highly conserved among echinoderm species. The magnitude and extent of these changes challenges the notion that conservation of early development in echinoderms is largely due to internal constraints that prohibit modification and instead suggests that natural selection actively maintains stability of inherently malleable trait developmental mechanisms over immense time periods. Knowing how and why natural selection changed during the evolution of nonfeeding larvae can also reveal why developmental mechanisms do and do not change in particular ways.
随着对发育机制的分析扩展到越来越多的物种，重要的不仅是要了解在进化过程中哪些特征被保留或改变了，还要了解其原因。在这方面，表现出极端表型差异的近缘物种可能具有独特的信息价值。一个恰当的例子是海胆属Heliocidaris，该属中的一些物种在经历了近5亿年以摄食性幼虫为特征的先前进化后，最近进化出了一种涉及非摄食性幼虫的生活史。由此产生的选择机制的转变在发育机制上产生了迅速且惊人的广泛变化，而这些发育机制在棘皮动物物种中原本是高度保守的。这些变化的程度和范围挑战了一种观念，即棘皮动物早期发育的保守性很大程度上是由于禁止改变的内部限制，相反，这表明自然选择在漫长的时间里积极维持着具有内在可塑性的性状发育机制的稳定性。了解在非摄食性幼虫的进化过程中自然选择如何以及为何发生变化，也可以揭示发育机制为何以特定方式变化或不变的原因。
