Developmental modularity has long been viewed as a hierarchical organization that facilitates evolution through modification or reuse of preexisting modules. More recently, developmental modularity has been proposed as a mechanism capable of driving rapid evolution of novel color pattern phenotypes between closely related taxa. In this scenario, recombination between modular cis-regulatory elements (CREs) generates novel phenotypes by shuffling genetic variation at preexisting color pattern modules into new arrangements. Recent functional evidence from Drosophila flies and Heliconius butterflies, however, provides a series of examples in which CREs function in multiple developmental contexts and are thus highly pleiotropic. The potential prevalence of pleiotropy in CRE function could be a barrier to the proposed importance of CRE modules as a mechanism for rapid evolutionary change. Here we review the concept of developmental modularity, some examples that suggest developmental modularity underlies pattern evolution, and recent evidence that indicates modular CREs may be less common than previously expected. This leads us to suggest that alternative, non-modular hypotheses should be considered alongside proposals of modular CREs. We then propose the concept of evolutionary modularity as a specific alternative to developmental modularity when discrete, seemingly modular, phenotypes occur in hybridizing taxa. We suggest that evolutionary modularity provides a potentially important pathway for exchange of phenotypic elements between hybridizing taxa independent of the underlying developmental architecture.

中文翻译：

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变化机制：关于模块化和多向性在多样化中的作用的基于人口的观点

长期以来，开发模块化一直被视为一种分层组织，它通过修改或重用预先存在的模块来促进进化。最近，已经提出了发育模块化作为一种​​机制，能够推动密切相关的分类群之间新型颜色模式表型的快速进化。在这种情况下，模块化顺式调控元件 (CRE) 之间的重组通过将先前存在的颜色模式模块的遗传变异改组为新的排列来产生新的表型。然而，最近来自果蝇和 Heliconius 蝴蝶的功能证据提供了一系列示例，其中 CRE 在多种发育环境中发挥作用，因此具有高度的多效性。CRE 功能中潜在的多效性可能会阻碍 CRE 模块作为快速进化变化机制的重要性。在这里，我们回顾了发展模块化的概念，一些例子表明发展模块化是模式进化的基础，最近的证据表明模块化 CRE 可能没有以前预期的那么普遍。这使我们建议，除了模块化 CRE 的提议外，还应考虑替代的、非模块化的假设。然后，当杂交分类群中出现离散的、看似模块化的表型时，我们提出了进化模块化的概念，作为发育模块化的特定替代方案。