非洲白鳳蝶的系統發生學與擬態翅紋的演化

文獻出處：Clark, R. & Vogler, A. P. (2009) A phylogenetic framwork for wing pattern evolutio in the mimetic Mocker Swallowtail Papilio dardanus. Molecular Ecology 18: 3872-3884.

簡介

非洲白鳳蝶(Papilio dardanus)被認為是貝氏擬態(Batesian mimicry)中的擬態者(mimic)，其雌雄二態性與雌性其中一型擬態大樺斑蝶(Danaus plexippus) 的表型長久以來被視為擬態生物學中的經典例子之一。本篇文章嘗試利用分子資料重建非洲白鳳蝶不同亞種間與不同區域間的親緣關係，嘗試找出其擬態斑紋的演化 時順。該研究使用兩個粒線體基因與數個與擬態斑紋有關或無關的核基因，重建不同亞種間的親緣關係。結果顯示粒線體基因在不同區域間呈現地理上的結構，並且 有較少的多樣性；而核基因間則無地理上的結構，並且基因序列間有多樣性的情形。定年的結果顯示，非洲白鳳蝶的種化約發生於2.9百萬年前，而擬態斑紋族群 的產生則在0.55-0.94百萬年前，擬態斑紋的產生在非洲白鳳蝶的原名亞種(P. d. dardanus)中是較早出現的，但仍晚於雌雄二態性。

Abstract

The Batesian mimetic swallowtail butterfly Papilio dardanus exhibits numerous distinct wing colour morphs whose evolutionary origins require large phenotypic shifts. A phylogenetic framework to study the history of these morphs was established by DNA sequencing of representative subspecies from sub-Saharan Africa and Indian Ocean islands. Two mitochondrial genes and the nuclear internal transcribed spacer marker revealed deeply separated eastern and western African mainland lineages, plus one lineage each on Madagascar and Grande Comore. These markers showed very little polymorphism within lineages. In contrast, markers genetically linked to the mimicry locus H, including the transcription factor invected and two adjacent amplified fragment length polymorphisms-derived sequences, showed high nucleotide diversity but were not geographically structured. Variation in the unlinked wingless gene showed a similar pattern, rejecting the hypothesis that high level of variation in the H region is due to balancing selection exerted by the phenotypes. The separation from a common ancestor with Papilio phorcas estimated at 2.9 Ma coincides with the origin of a mimicry model, Danaus chrysippus. However, the model reached Africa only at the time of the internal splits of P. dardanus mtDNA groups, here estimated at 0.55-0.94 Ma. The nuclear genome shows less geographic structure and may not track recent population differentiation, suggesting that widespread mimicry morphs have arisen early in the evolution of the P. dardanus lineage, although after the male-female dimorphism which is ancestral. The current wide distribution of P. dardanus and population subdivision evident from mtDNA may have been achieved only with the spread of the models across Africa.