自然界中，不少蝴蝶掌握借助“拟态”躲避天敌的本领。一项最新研究发现，蝴蝶的拟态功能由其体内的“超级基因簇”决定。
英法两国研究人员在8月份的《自然》杂志上发表论文说，他们选取了一种生长在亚马逊热带雨林地区的釉蛱蝶进行研究。这种蝴蝶能通过改变翅膀花纹，“伪装”成那些味道不佳的蝴蝶，从而躲过鸟类的捕食。
研究人员在分析该种蝴蝶体内的染色体序列后发现，一种染色体内部存在多种变异，各变异组合形成了“超级基因簇”，最终决定着拟态的花纹。
参与研究的法国自然历史博物馆马蒂厄·若龙博士形象地用“变形金刚”来解释这个基因簇的作用，他说，蝴蝶可谓昆虫世界的变形金刚，经过简单的基因切换组合就可实现拟态。
此外，研究人员表示，“超级基因簇”同样存在于飞蛾等其他昆虫体内，使它们既可模仿其他同类，又能模仿周围环境。(生物谷 Bioon.com)
doi:10.1038/nature10341
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Chromosomal rearrangements maintain a polymorphic supergene controlling butterfly mimicry
Mathieu Joron; Lise Frezal; Robert T. Jones; Nicola L. Chamberlain; Siu F. Lee; Christoph R. Haag; Annabel Whibley; Michel Becuwe; Simon W. Baxter; Laura Ferguson; Paul A. Wilkinson; Camilo Salazar; Claire Davidson; Richard Clark; Michael A. Quail; Helen Beasley; Rebecca Glithero; Christine Lloyd; Sarah Sims; Matthew C. Jones; Jane Rogers; Chris D. Jiggins; Richard H. ffrench-Constant
Supergenes are tight clusters of loci that facilitate the co-segregation of adaptive variation, providing integrated control of complex adaptive phenotypes1. Polymorphic supergenes, in which specific combinations of traits are maintained within a single population, were first described for ‘pin’ and ‘thrum’ floral types in Primula1 and Fagopyrum2, but classic examples are also found in insect mimicry3, 4, 5 and snail morphology6. Understanding the evolutionary mechanisms that generate these co-adapted gene sets, as well as the mode of limiting the production of unfit recombinant forms, remains a substantial challenge7, 8, 9, 10. Here we show that individual wing-pattern morphs in the polymorphic mimetic butterfly Heliconius numata are associated with different genomic rearrangements at the supergene locus P. These rearrangements tighten the genetic linkage between at least two colour-pattern loci that are known to recombine in closely related species9, 10, 11, with complete suppression of recombination being observed in experimental crosses across a 400-kilobase interval containing at least 18 genes. In natural populations, notable patterns of linkage disequilibrium (LD) are observed across the entire P region. The resulting divergent haplotype clades and inversion breakpoints are found in complete association with wing-pattern morphs. Our results indicate that allelic combinations at known wing-patterning loci have become locked together in a polymorphic rearrangement at the P locus, forming a supergene that acts as a simple switch between complex adaptive phenotypes found in sympatry. These findings highlight how genomic rearrangements can have a central role in the coexistence of adaptive phenotypes involving several genes acting in concert, by locally limiting recombination and gene flow.
