Summary Replicated trait evolution can provide insights into the mechanisms underlying the evolution of biodiversity. One example of replicated evolution is the awn, an organ elaboration in grass inflorescences. Awns are likely homologous to leaf blades. We hypothesized that awns have evolved repeatedly because a conserved leaf blade developmental program is continuously activated and suppressed over the course of evolution, leading to the repeated emergence and loss of awns. To evaluate predictions arising from our hypothesis, we used ancestral state estimations, comparative genetics, anatomy, and morphology to trace awn evolution. We discovered that awned lemmas that evolved independently share similarities in developmental trajectory. In addition, in two species with independently derived awns and differing awn morphologies (Brachypodium distachyon and Alopecurus myosuroides), we found that orthologs of the YABBY transcription factor gene DROOPING LEAF are required for awn initiation. Our analyses of awn development in Brachypodium distachyon, Alopecurus myosuroides, and Holcus lanatus also revealed that differences in the relative expansion of awned lemma compartments can explain diversity in awn morphology at maturity. Our results show that developmental conservation can underlie replicated evolution and can potentiate the evolution of morphological diversity.

中文翻译：

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发育限制是草芒复制进化的基础


总结 复制性状进化可以深入了解生物多样性进化的潜在机制。复制进化的一个例子是芒，这是草花序中的器官阐述。芒可能与叶片同源。我们假设芒反复进化，是因为保守的叶片发育程序在进化过程中不断被激活和抑制，导致芒的反复出现和丧失。为了评估由我们的假设得出的预测，我们使用了祖先状态估计、比较遗传学、解剖学和形态学来追踪芒的进化。我们发现，独立进化的遮阳词元在发展轨迹上具有相似之处。此外，在两个具有独立来源的芒和不同芒形态的物种 （Brachypodium distachyon 和 Alopecurus myosuroides） 中，我们发现 YABBY 转录因子基因 DROOPING LEAF 的直系同源物是芒起始所必需的。我们对 Brachypodium distachyon、Alopecurus myosuroides 和 Holcus lanatus 的芒发育分析还表明，芒状稃室相对扩展的差异可以解释成熟时芒形态的多样性。我们的结果表明，发育守恒可以是复制进化的基础，并且可以增强形态多样性的进化。