Birds are the most diversified terrestrial vertebrates due to highly diverse integumentary organs that enable robust adaptability to various eco-spaces. Here we show that this complexity is built upon multi-level regional specifications. Across-the-body (macro-) specification includes the evolution of beaks and feathers as new integumentary organs that are formed with regional specificity. Within-an-organ (micro-) specification involves further modifications of organ shapes. We review recent progress in elucidating the molecular mechanisms underlying feather diversification as an example. (1) β-Keratin gene clusters are regulated by typical enhancers or high order chromatin looping to achieve macro- and micro-level regional specification, respectively. (2) Multi-level symmetry-breaking of feather branches confers new functional forms. (3) Complex color patterns are produced by combinations of macro-patterning and micro-patterning processes. The integration of these findings provides new insights toward the principle of making a robustly adaptive bio-interface.

鸟类是最多样化的陆生脊椎动物，因为它们具有高度多样化的外皮器官，能够对各种生态空间具有强大的适应性。在这里，我们表明这种复杂性是建立在多层次的区域规范之上的。全身（宏观）规范包括喙和羽毛作为具有区域特异性形成的新外皮器官的进化。器官内（微）规范涉及器官形状的进一步修改。我们回顾了最近在阐明羽毛多样化的分子机制方面取得的进展。(1) β-角蛋白基因簇受典型增强子或高级染色质环调控，分别实现宏观和微观水平的区域规范。(2)羽枝的多层次对称破缺赋予新的功能形态。(3) 复杂的彩色图案是通过宏观图案和微观图案工艺的组合产生的。这些发现的整合为制作稳健自适应生物界面的原理提供了新的见解。