2009年9月22日 星期二


文獻來源: Kodandaramaiah U. 2009. Eyespot evolution: phylogenetic insights from Junonia and related butterfly genera (Nymphalidae: Junoniini). Evolution & Development 11(5): 489-497. [摘要網址]

Butterfly eyespots have been the focus of a number of developmental and evolutionary studies. However, a phylogenetic component has rarely been explicitly incorporated in these studies. In this study, I utilize a phylogeny to trace the evolution of eyespot number and position on the wing in a group of nymphalid butterflies, the subtribe Junoniini. These butterflies have two kinds of eyespot arrangements which I refer to as Serial and Individual. In the Serial arrangement, eyespots are placed in a series on compartments 1−6 (counting from the anterior wing margin). In the Individual arrangement, eyespots are isolated on specific compartments, ranging from 1 to 4 in number. This can be divided into four subtypes based on the number and positions of eyespots. I map the evolution of these five arrangements over a phylogeny of Junoniini reconstructed with ca. 3000 base pairs of sequence data from three genes. The results show that almost all arrangements have evolved at least twice, with multiple shifts between them by addition and deletion of eyespots. I propose a model involving genetic or developmental coupling between eyespots in specific compartments to explain these shifts. I discuss their evolution in light of existing knowledge about their development. I also discuss potential explanations for functional significance of the eyespot patterns found in the group. Differential selection for and against eyespots, both at different times over the phylogeny and in different regions, have driven the evolution of eyespot arrangements. The study throws open many questions about the adaptive significance of eyespots and the developmental underpinnings of the various arrangements.


文獻來源: Ferguson LC, Jiggins CD. 2009. Shared and divergent expression domains on mimetic Heliconius wings. Evolution & Development 11(5): 498-512. [摘要網址]

毒蝶屬(Heliconius)為擬態生物學中穆氏擬態最具代表性的例子,自1879年穆氏擬態發表後,即吸引生物學家從多許多生物議題探討此龐大擬態群的產生,如行為學、演化學、化學生物學、群聚生態學,至近代的分子生物學、發育生物學等,但該擬態群的演化歷程仍然有許多的疑問未解。本篇文章從發育生物學的角度出發,嘗試以兩種毒蝶屬的物種,H. erato與H. melpomene,探索其相似翅紋的發育來源。作者觀察蛹發育時期時有關翅紋色素的基因發育表現,發現在兩個物種中,有關所有有關朱紅色色素形成的基因皆有關連,但其表現的形式有顯著的差異。兩個未在H. erato中研究的基因,scarlet與kf,增強H. melpomene的猩紅色素在翅紋中的呈現,可能暗示此兩種基因也在擬態的其他成員中參與翅紋的調控。

Heliconius butterfly wing patterns show repeated convergence between species and have adaptive value in mimicry and mate choice, offering an opportunity to connect adaptive changes in phenotype with their underlying genotypes. Here we study forewing ommochrome pigmentation in Heliconius melpomene. We clone two new ommochrome pathway genes for the Lepidoptera, karmoisin and kynurenine formamidase (kf ), and analyze the expression patterns of all known ommochrome genes across pupal wing development. In combination with published work, this generates the first comparative gene expression data for the co-mimics Heliconius erato and H. melpomene. In both species cinnabar expression correlates with the forewing band, but the expression pattern of vermillion differs significantly between the mimics. This demonstrates that both shared and divergent expression patterns are associated with mimetic phenotypes between Heliconius species. Two genes not studied in H. erato, scarlet and possibly kf, also show enhanced expression in the forewing band of H. melpomene, implying co-ordinated upregulation of several members of this biosynthetic pathway during pattern formation.

2009年9月21日 星期一

透明小魚蝦的群聚可能是一種閃避視覺系捕食者的防禦策略, 並牽涉數量擬態(或稱社會擬態)

文獻來源: Carvalho LN, Zuanon J, Sazima I. 2009. The almost invisible league: crypsis and association between minute fishes and shrimps as a possible defence against visually hunting predators. Neotropical Ichthyology 4(2): doi: 10.1590/S1679-62252006000200008

Camouflage is one of the most widespread defence modes used by substrate-dwelling animals, whereas transparency is generally found in open-water organisms. Both these defence types are regarded as effective against visually guided predators. We present here three assemblages of similarly-sized freshwater fish and shrimp species which apparently rely on camouflage and transparency to evade some of their potential predators. In one of the associations, there is a transition from cryptic colours and translucency to transparency of the component species according to the position each of them occupies in the habitat. The likeness between the fishes and the shrimps is here regarded as a type of protective association similar to numerical or social mimicry. Additionally, we suggest that the assemblage may contain Batesian-like mimicry components.

圖片連結: Aquaristik ohne Geheimnisse


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.

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。

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.