Müllerian mimicry strongly exemplifies the power of natural selection. However, the exact measure of such adaptive phenotypic convergence and the possible causes of its imperfection often remain unidentified. Here, we first quantify wing colour pattern differences in the forewing region of 14 co-mimetic colour pattern morphs of the butterfly species Heliconius erato and Heliconius melpomene and measure the extent to which mimicking colour pattern morphs are not perfectly identical. Next, using gene-editing CRISPR/Cas9 KO experiments of the gene WntA, which has been mapped to colour pattern diversity in these butterflies, we explore the exact areas of the wings in which WntA affects colour pattern formation differently in H. erato and H. melpomene. We find that, while the relative size of the forewing pattern is generally nearly identical between co-mimics, the CRISPR/Cas9 KO results highlight divergent boundaries in the wing that prevent the co-mimics from achieving perfect mimicry. We suggest that this mismatch may be explained by divergence in the gene regulatory network that defines wing colour patterning in both species, thus constraining morphological evolution even between closely related species.

中文翻译：

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Heliconius 蝴蝶之间的完美模仿受到遗传和发育的限制

缪勒拟态有力地证明了自然选择的力量。然而，这种适应性表型收敛的确切措施及其不完善的可能原因通常仍未确定。在这里，我们首先量化了蝴蝶物种 Heliconiuserato 和 Heliconius melpomene 的 14 种共同模拟颜色图案变形的前翅区域的翅膀颜色图案差异，并测量模仿颜色图案变形的程度不完全相同。接下来，我们使用 WntA 基因的基因编辑 CRISPR/Cas9 KO 实验，该实验已映射到这些蝴蝶的颜色模式多样性，我们探索了 WntA 对 H.erato 和 H. .melpomene。我们发现，虽然共同模仿物之间前翅图案的相对大小通常几乎相同，但 CRISPR/Cas9 KO 结果突出了机翼中的不同边界，这阻止了共同模仿物实现完美模仿。我们认为，这种不匹配可以通过定义两个物种翅膀颜色模式的基因调控网络的差异来解释，从而限制了即使在密切相关的物种之间的形态进化。