A neo-W chromosome in a tropical butterfly links colour pattern, male-killing, and speciation.
A neo-W chromosome in a tropical butterfly links colour pattern, male-killing, and speciation.
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DOI：
10.1098/rspb.2016.0821
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发表时间：
2016-07-27
期刊：
影响因子：
--
通讯作者：
Ffrench-Constant R
中科院分区：
文献类型：
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作者：
Smith DA;Gordon IJ;Traut W;Herren J;Collins S;Martins DJ;Saitoti K;Ireri P;Ffrench-Constant R
性对抗选择可以驱动性染色体和物种形成本身的进化。热带蝴蝶非洲女王 Danaus chrysippus 显示出两种这样的性对抗表型，第一个是性别相关的颜色模式，第二个是对雄性致死性、母系遗传软体动物螺旋体 (Spiroplasma ixodeti) 的易感性，这种动物导致雄性卵和一龄幼虫大约 100% 死亡率。重要的是，这种死亡率不受父本感染状况的影响，并且螺原体的水平传播尚不清楚。在东非，以内罗毕为中心的狭窄混合区中，男性杀害女王的现象十分普遍。这个混合区将具有不同颜色图案的异域亚种分开。在这里，我们展示了新W染色体，即W（雌性）染色体和控制颜色模式和雄性杀伤的常染色体之间的融合，将两种表型联系起来，从而驱动整个杂交区的物种形成。对内罗毕周围新W的群体遗传学的研究表明，颜色模式和雄性杀手易感性之间的相互作用限制了D. chrysippus两个亚种之间的基因流动。我们的研究结果表明，性别、颜色模式、雄性杀戮和新 W 染色体之间复杂的相互作用如何建立了一个遗传“水槽”，使两个亚种保持分离。因此，新W与雄性捕杀之间的联系为正在进行的物种形成过程提供了“确凿的证据”。
Sexually antagonistic selection can drive both the evolution of sex chromosomes and speciation itself. The tropical butterfly the African Queen, Danaus chrysippus, shows two such sexually antagonistic phenotypes, the first being sex-linked colour pattern, the second, susceptibility to a male-killing, maternally inherited mollicute, Spiroplasma ixodeti, which causes approximately 100% mortality in male eggs and first instar larvae. Importantly, this mortality is not affected by the infection status of the male parent and the horizontal transmission of Spiroplasma is unknown. In East Africa, male-killing of the Queen is prevalent in a narrow hybrid zone centred on Nairobi. This hybrid zone separates otherwise allopatric subspecies with different colour patterns. Here we show that a neo-W chromosome, a fusion between the W (female) chromosome and an autosome that controls both colour pattern and male-killing, links the two phenotypes thereby driving speciation across the hybrid zone. Studies of the population genetics of the neo-W around Nairobi show that the interaction between colour pattern and male-killer susceptibility restricts gene flow between two subspecies of D. chrysippus. Our results demonstrate how a complex interplay between sex, colour pattern, male-killing, and a neo-W chromosome, has set up a genetic ‘sink' that keeps the two subspecies apart. The association between the neo-W and male-killing thus provides a ‘smoking gun' for an ongoing speciation process.