控制斑紋的基因重建演化歷史，顯示穆氏擬態的蝴蝶可能有共演化關係
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| photo from Heliconius.org |
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| photo from Kronforst Lab |
標題：Wing patterning genes and coevolution of Müllerian mimicry in Heliconius butterflies: Support from phylogeography, cophylogeny, and divergence times.
摘要
Examples of long-term coevolution are rare among free-living organisms. Mullerian mimicry in Heliconius butterflies had been suggested as a key example of coevolution by early genetic studies. However, research over the last two decades has been dominated by the idea that the best-studied comimics, H. erato and H. melpomene, did not coevolve at all. Recently sequenced genes associated with wing color pattern phenotype offer a new opportunity to resolve this controversy. Here, we test the hypothesis of coevolution between H. erato and H. melpomene using Bayesian multilocus analysis of five color pattern genes and five neutral genetic markers.We first explore the extent of phylogenetic agreement versus conflict between the different genes. Coevolution is then tested against three aspects of the mimicry diversifications: phylogenetic branching patterns, divergence times, and, for the first time, phylogeographic histories.We show that all three lines of evidence are compatible with strict coevolution of the diverse mimicry wing patterns, contrary to some recent suggestions. Instead, these findings tally with a coevolutionary diversification driven primarily by the ecological force of Mullerian mimicry.
穆氏擬態的毒蝶(Heliconius)就是很像又都有毒，這麼相像的斑紋到底怎麼來的？這是一個很大的疑問。而且，很多人認為兩個物種長的這麼像又分佈在同一個地方，承受一樣的天擇壓力，那麼，這個斑紋應該是共演化(coevolution)的關係吧？
大約十幾年前時有James Mallet有寫文章特別討論過，那個時候特別提到，雖然毒蝶的每個斑紋都很像，但這僅是斑紋上的趨同，不是兩個物種的共演化。然而在這十年間，分子生物技術的發展大量應用在毒蝶擬態的研究上，無論是控制斑紋的基因，或是與種化有關的基因都被找出來了，如果重新檢視有沒有共演化這個問題，會不會不一樣呢？
於是H. erato 與H. melpomene這兩個經典的穆氏擬態分類群又上場了。作者利用了五個控制斑紋的基因 (optix, bves, kinesin, GPCR, and VanGogh)跟五個中性基因 (COI and COII, plus four nuclear genes: SUMO, Suz12, 2654, and CAT)再次重建親緣關係。作者透過比較兩個物種的親緣關係的樹型、分化的時間與生物地理的演化歷史，重新分析這兩個物種的演化歷史。結果發現這兩個物種在這三方面的分析中都支持兩者間的共演化關係，樹型相似、斑紋分化時間相似，生物地理的分析也相關，這個結果似乎提供了一個與之前完全相反的證據，支持新熱帶蝴蝶的擬態斑紋的共演化。
這個文章有另一個值得討論的地方，以前總認為控制擬態的斑紋，或是說明顯受到天擇/性擇的基因，是不能用來重建物種的親緣關係，因為會有無法正確反應物種演化歷程的疑慮，因此總是會選擇被天擇/性擇影響比較小，比較「中性」的基因來重建親緣關係，可是這個文章用了應該明顯受到天擇影響的基因，反而呈現了完全不同的理論與故事，這給研究演化的科學家們一個新的思考方向，或許使用以前不被考慮的基因，更能反應該性狀的演化歷程。
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