Convergent evolution is a widespread phenomenon. While there are many examples of convergent evolution at the phenotypic scale, convergence at the molecular level has been more difficult to identify. A classic example of convergent evolution across scales is that of the digestive lysozyme found in ruminants and Colobine monkeys. These herbivorous species rely on foregut fermentation, which has evolved to function more optimally under acidic conditions. Here, we explored if rodents with similar dietary strategies and digestive morphologies have convergently evolved a lysozyme with digestive functions. At the phenotypic level, we find that rodents with bilocular stomach morphologies exhibited a lysozyme that maintained higher relative activities at low pH values, similar to the lysozymes of ruminants and Colobine monkeys. Additionally, the lysozyme of shared a similar predicted protonation state as that observed in previously identified digestive lysozymes. However, we found limited evidence of positive selection acting on the lysozyme gene in foregut-fermenting species and did not identify patterns of convergent molecular evolution in this gene. This study emphasizes that phenotypic convergence need not be the result of convergent genetic modifications, and we encourage further exploration into the mechanisms regulating convergence across biological scales.

中文翻译：

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前肠发酵啮齿动物、反刍动物和灵长类动物胃溶菌酶的功能趋同并不归因于趋同分子进化

趋同进化是一种普遍存在的现象。虽然在表型尺度上有很多趋同进化的例子，但分子水平上的趋同却更难以识别。跨尺度趋同进化的一个典型例子是反刍动物和疣猴中发现的消化溶菌酶。这些草食性物种依赖于前肠发酵，这种发酵已经进化到在酸性条件下发挥更佳功能。在这里，我们探讨了具有相似饮食策略和消化形态的啮齿动物是否趋同进化出具有消化功能的溶菌酶。在表型水平上，我们发现具有双眼胃形态的啮齿动物表现出在低pH值下保持较高相对活性的溶菌酶，类似于反刍动物和疣猴的溶菌酶。此外，溶菌酶具有与先前鉴定的消化溶菌酶中观察到的相似的预测质子化状态。然而，我们在前肠发酵物种中发现了作用于溶菌酶基因的正向选择的证据有限，并且没有识别出该基因中趋同分子进化的模式。这项研究强调表型趋同不一定是趋同基因修饰的结果，我们鼓励进一步探索跨生物尺度调节趋同的机制。