21世紀的超基因觀點：貝氏擬態、性染色體與演化適應的重組抑制機制

photo from doublesex is a mimicry supergene

標題：The status of supergenes in the 21st century: recombination suppression in Batesian mimicry and sex chromosomes and other complex adaptations.


摘要

I review theoretical models for the evolution of supergenes in the cases of Bate- sian mimicry in butterflies, distylous plants and sex chromosomes. For each of these systems, I outline the genetic evidence that led to the proposal that they involve multiple genes that interact during ‘complex adaptations’, and at which the mutations involved are not unconditionally advantageous, but show advanta- ges that trade-off against some disadvantages. I describe recent molecular genetic studies of these systems and questions they raise about the evolution of sup- pressed recombination. Nonrecombining regions of sex chromosomes have long been known, but it is not yet fully understood why recombination suppression repeatedly evolved in systems in distantly related taxa, but does not always evolve. Recent studies of distylous plants are tending to support the existence of recom- bination-suppressed genome regions, which may include modest numbers of genes and resemble recently evolved sex-linked regions. For Batesian mimicry, however, molecular genetic work in two butterfly species suggests a new super- gene scenario, with a single gene mutating to produce initial adaptive pheno-types, perhaps followed by modifiers specifically refining and perfecting the new phenotype.

先說，這篇很難，完全在說分子生物學層級的機制。

作者整理有關貝氏擬態、性別決定與植物的二型花柱(distyly)討論基因重組與超基因的分子演化機制。這邊稍微整理貝氏擬態的部分，主要是談到有關這60年來藉由大鳳蝶 (Papilio memnon)、玉帶鳳蝶(P. polytes)與非洲白鳳蝶 (P. dardanus)的遺傳學與基因體學的研究，討論超基因如何出現的分子機制，如何透過基因重組的方式讓控制不同區域斑紋的基因逐漸在染色體上靠攏，作者整理兩個假說，說明兩個以上的擬態斑紋基因是如何出現在基因體內的兩種機制，分別是同染色體的調控與異染色體的調控（內文圖一）。這個整理對於擬態生物學關於分子層級的調控機制的研究提供一個統整性的框架。

未來將不再只是毒蝶內的穆氏擬態，貝氏擬態的背後神秘的作用機制也會越來越明朗。