眼蛺蝶族的眼紋演化趨勢以及在警戒性與婚配系統演化上的啟示

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]

Abstract
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.

兩種具共擬態關係毒蛺蝶視色素基因作用路徑之趨同與趨異表現

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]

簡介
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。

Abstract
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.

[Article]Multimodal warning signals for a multiple predator world

Nature 455, 96-99 (4 September 2008) | doi:10.1038/nature07087; Received 10 February 2008; Accepted 14 May 2008

Multimodal warning signals for a multiple predator world

John M. Ratcliffe^1,3 & Marie L. Nydam^2,3

1. Center for Sound Communication, Institute of Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
2. Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York 14853, USA
3. These authors contributed equally to this work.

Correspondence to: John M. Ratcliffe^1,3Marie L. Nydam^2,3 Correspondence and requests for materials should be addressed to M.L.N. (Email: mln32@cornell.edu) or J.M.R. (Email: jmr@biology.sdu.dk).

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Abstract

Aposematism is an anti-predator defence, dependent on a predator's ability to associate unprofitable prey with a prey-borne signal¹. Multimodal signals should vary in efficacy according to the sensory systems of different predators; however, until now, the impact of multiple predator classes on the evolution of these signals had not been investigated^{2, 3}. Here, using a community-level molecular phylogeny to generate phylogenetically independent contrasts, we show that warning signals of tiger moths vary according to the seasonal and daily activity patterns of birds and bats—predators with divergent sensory capacities. Many tiger moths advertise chemical defence^{4, 5} using conspicuous colouration and/or ultrasonic clicks^{3, 6}. During spring, when birds are active and bats less so, we found that tiger moths did not produce ultrasonic clicks. Throughout both spring and summer, tiger moths most active during the day were visually conspicuous. Those species emerging later in the season produced ultrasonic clicks; those that were most nocturnal were visually cryptic. Our results indicate that selective pressures from multiple predator classes have distinct roles in the evolution of multimodal warning displays now effective against a single predator class. We also suggest that the evolution of acoustic warning signals may lack the theoretical difficulties associated with the origination of conspicuous colouration.

[Article]A Conserved Supergene Locus Controls Colour Pattern Diversity in Heliconius Butterflies

Link: http://0rz.tw/733NG
Abstract: We studied whether similar developmental genetic mechanisms are involved in both convergent and divergent evolution. Mimetic insects are known for their diversity of patterns as well as their remarkable evolutionary convergence, and they have played an important role in controversies over the respective roles of selection and constraints in adaptive evolution. Here we contrast three butterfly species, all classic examples of Müllerian mimicry. We used a genetic linkage map to show that a locus, Yb, which controls the presence of a yellow band in geographic races of Heliconius melpomene, maps precisely to the same location as the locus Cr, which has very similar phenotypic effects in its co-mimic H. erato. Furthermore, the same genomic location acts as a “supergene”, determining multiple sympatric morphs in a third species, H. numata. H. numata is a species with a very different phenotypic appearance, whose many forms mimic different unrelated ithomiine butterflies in the genus Melinaea. Other unlinked colour pattern loci map to a homologous linkage group in the co-mimics H. melpomene and H. erato, but they are not involved in mimetic polymorphism in H. numata. Hence, a single region from the multilocus colour pattern architecture of H. melpomene and H. erato appears to have gained control of the entire wing-pattern variability in H. numata, presumably as a result of selection for mimetic “supergene” polymorphism without intermediates. Although we cannot at this stage confirm the homology of the loci segregating in the three species, our results imply that a conserved yet relatively unconstrained mechanism underlying pattern switching can affect mimicry in radically different ways. We also show that adaptive evolution, both convergent and diversifying, can occur by the repeated involvement of the same genomic regions.