為何車前燈蛾的翅紋多樣性可以長期存在？

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Nokelainen O, Hegna RH, Reudler JH, Lindstedt C, Mappes J. 2011. Trade-off between warning signal efficacy and mating success in the wood tiger moth. Proc. R. Soc. B. doi: 10.1098/rspb.2011.0880 [full text]

從演化的觀點來看，特徵選汰應傾向於對物種存活有利的方式，並且，後期這些基因特質應達到穩定且妨礙多態型的存在，但有許多警戒色的例子顯示多態型的物種是可以同時存在於相同族群中，其顯示不同型態之特徵可能具有不同優勢存在，或其可能具有相同功效。在此，作者以具有明顯翅紋變異的白色及黃色車前燈蛾(Parasemia plantaginis)作為獵物，以藍山雀(Parus caeruleus)作為捕食者測試翅紋警戒色在存活率和繁殖成功率之間的關係。結果顯示：(a)捕食者對於黃色翅紋有較長的攻擊延遲時間 (b)黃色翅紋的個體存活率比白色翅紋的個體好 (c)白色翅紋的個體繁殖成功率比黃色翅紋個體好，因此，作者認為此結果正好為車前燈蛾白色及黃色翅紋同時共存於自然界作一個很好的解釋。

毒蛺蝶的共域多態性擬態乃經由染色體重組維繫

文獻來源: Joron et al. (2011) Chromosomal rearrangements maintain a polymorphic supergene controlling butterfly mimicry. Nature doi:10.1038/nature10341

Abstract
Supergenes are tight clusters of loci that facilitate the co-segregation of adaptive variation, providing integrated control of complex adaptive phenotypes. Polymorphic supergenes, in which specific combinations of traits are maintained within a single population, were first described for ‘pin’ and ‘thrum’ floral types in Primula and Fagopyrum, but classic examples are also found in insect mimicry and snail morphology. 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 challenge. 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 species, 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.