The concept that complex ancestral traits can never be re-acquired after their loss has grown popular since its initial formulation and it’s often referred to as Dollo’s law. Nonetheless, several macroevolutionary evidences - along with molecular ones - suggest instances where complex phenotypes could have been lost throughout a clade evolutionary history and subsequently reverted to their former state in derived lineages. One of the first and most notable rejection of Dollo’s law is represented by wing evolution in phasmids: this polyneopteran order of insects - which comprises stick and leaf insects - has played a central role in initiating a long-standing debate on the topic. In this study, a novel and comprehensive time-tree - including over 300 Phasmatodea species - is used as a framework for investigating wing’s evolutionary patterns in the clade. Despite accounting for several possible biases and sources of uncertainty, macroevolutionary analyses consistently support a dynamic and reversible evolution of wings, with multiple transitions to ancestral states taking place after their loss. Our findings suggest that wings and flight are decoupled from Phasmatodea diversification dynamics and that brachyptery is an unstable state, unless when co-opted for non-aerodynamic adaptations. We also explored how different assumptions of wings’ reversals probability could impact their inference: we found that until reversals are assumed to be over 30 times more unlikely than losses, they are consistently retrieved despite uncertainty in tree and model parameters. Our findings demonstrate that wings evolution can be a reversible and dynamic process in phasmids and contribute to shape our understanding of how complex phenotypes evolve.

中文翻译：

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宏观进化分析为缨翅进化作为可逆过程提供了新证据

自最初提出以来，复杂的祖先特征在失去后永远无法重新获得的概念已经变得流行，并且通常被称为多洛定律。尽管如此，一些宏观进化证据 - 以及分子证据 - 表明复杂表型可能在整个进化枝进化历史中丢失并随后在衍生谱系中恢复到以前的状态的情况。对多洛定律的第一个也是最显着的拒绝之一是 phasmids 的翅膀进化：这种多翅目昆虫 - 包括棒虫和叶虫 - 在启动关于该主题的长期辩论中发挥了核心作用。在这项研究中，一种新颖而全面的时间树——包括超过 300 种 Phasmatodea 物种——被用作研究进化枝中翼进化模式的框架。尽管考虑了几种可能的偏差和不确定性来源，宏观进化分析始终支持翅膀的动态和可逆进化，在失去后会发生多次向祖先状态的转变。我们的研究结果表明，翅膀和飞行与 Phasmatodea 的多样化动力学脱钩，并且短翼是一种不稳定的状态，除非被选择进行非空气动力学适应。我们还探讨了翼的逆转概率的不同假设如何影响他们的推论：我们发现，在假设逆转之前，逆转的可能性是损失的 30 倍以上，尽管树和模型参数不确定，但它们始终被检索。我们的研究结果表明，翅膀进化可以是 phasmids 中的一个可逆和动态过程，并有助于塑造我们对复杂表型如何进化的理解。