Department of Animal Evolution and Biodiversity, Johann-Friedrich-Blumenbach Institute of Zoology and Anthropology, University of Göttingen, Göttingen, Germany.
BMC Ecol Evol. 2022 May 12;22(1):62. doi: 10.1186/s12862-022-02018-5.
The re-evolution of complex characters is generally considered impossible, yet, studies of recent years have provided several examples of phenotypic reversals shown to violate Dollo's law. Along these lines, the regain of wings in stick and leaf insects (Phasmatodea) was hypothesised to have occurred several times independently after an ancestral loss, a scenario controversially discussed among evolutionary biologists due to overestimation of the potential for trait reacquisition as well as to the lack of taxonomic data.
We revisited the recovery of wings by reconstructing a phylogeny based on a comprehensive taxon sample of over 500 representative phasmatodean species to infer the evolutionary history of wings. We additionally explored the presence of ocelli, the photoreceptive organs used for flight stabilisation in winged insects, which might provide further information for interpreting flight evolution. Our findings support an ancestral loss of wings and that the ancestors of most major lineages were wingless. While the evolution of ocelli was estimated to be dependent on the presence of (fully-developed) wings, ocelli are nevertheless absent in the majority of all examined winged species and only appear in the members of few subordinate clades, albeit winged and volant taxa are found in every euphasmatodean lineage.
In this study, we explored the evolutionary history of wings in Phasmatodea and demonstrate that the disjunct distribution of ocelli substantiates the hypothesis on their regain and thus on trait reacquisition in general. Evidence from the fossil record as well as future studies focussing on the underlying genetic mechanisms are needed to validate our findings and to further assess the evolutionary process of phenotypic reversals.
复杂特征的重新进化通常被认为是不可能的，但近年来的研究提供了几个表型反转的例子，这些例子表明违背了 Dollo 法则。沿着这条线，竹节虫（Phasmatodea）翅膀的恢复被假设在祖先丧失后独立发生了多次，这种情况在进化生物学家中引起了争议，原因是对特征重新获得的潜力估计过高，以及缺乏分类学数据。
我们通过重建一个基于超过 500 种代表性竹节虫物种的综合分类群样本的系统发育来重新研究翅膀的恢复，以推断翅膀的进化历史。我们还探索了眼点的存在，眼点是用于稳定飞行的感光器官，这可能为解释飞行进化提供进一步的信息。我们的发现支持翅膀的祖先丧失，并且大多数主要谱系的祖先都是无翅的。虽然眼点的进化被估计依赖于（完全发育的）翅膀的存在，但在大多数检查过的有翅物种中，眼点仍然不存在，而且只出现在少数从属分支中，尽管在每个 euphasmatodean 谱系中都发现了有翅和飞翔的类群。
在这项研究中，我们探索了竹节虫翅膀的进化历史，并表明眼点的不连续分布证实了它们的恢复假说，从而证实了特征的重新获得。化石记录的证据以及未来专注于潜在遗传机制的研究需要验证我们的发现，并进一步评估表型反转的进化过程。
