蝶類食性範圍是否可算是演化可塑性促進種化的範例?

Butterfly host plant range: an example of plasticity as a promoter of speciation?

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Evolutionary Ecology (2009) 23: 137-146

Sören Nylin¹ and Niklas Janz¹

Mary Jane West-Eberhard 曾主張可塑性可能是促進演化發生和多樣化的首要條件。在本文中，作者以蛺蝶為例子探討植食性昆蟲透過此過程演化的可能性。作者討論寄主植物與可塑性之間相連的方式，並呈現作者對於 West-Eberhard 的腳本如何可能導致由寄主利用所驅動的種化之闡釋。作者也在本文中回顧一些植物利用的多樣性促使植食性昆蟲多樣化之實例，最終討論這是否暗示了一個由可塑性驅動種化的角色。作者找到一個作者的理論(植食性昆蟲多樣化是由寄主範圍波動驅使)與作者對West-Eberhard的理論所作最有效率的解釋，兩者之間緊密的概念連結。一個主要未解決的議題是寄主植物範圍廣泛的程度是由於適應可塑性伴隨著為利用不同植物設計的遺傳機制的專用模組。

Abstract
Mary Jane West-Eberhard has suggested that plasticity may be of primary importance in promoting evolutionary innovation and diversification. Here, we explore the possibility that the diversification of phytophagous insects may have occurred through such a process, using examples from nymphalid butterflies. We discuss the ways in which host plant range is connected to plasticity and present our interpretation of how West-Eberhard’s scenario may result in speciation driven by plasticity in host utilization. We then review some of the evidence that diversity of plant utilization has driven the diversification of phytophagous insects and finally discuss whether this suggests a role for plasticity-driven speciation. We find a close conceptual connection between our theory that the diversification of phytophagous insects has been driven by oscillations in host range, and our personal interpretation of the most efficient way in which West-Eberhard’s theory could account for plasticity-driven speciation. A major unresolved issue is the extent to which a wide host plant range is due to adaptive plasticity with dedicated modules of genetic machinery for utilizing different plants.

大象對蝴蝶：大型草食動物在兩個熱帶世界的演化歷史所扮演的生態角色

Elephants versus butterflies: the ecological role of large herbivores in the evolutionary history of two tropical worlds Journal of Biogeography 30(9):1357–1380

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Cris Cristoffer1* and Carlos A. Peres2 1CES/CEVN, Luke Air Force Base, AZ, USA, 2Centre for Ecology, Evolution & Conservation, University of East Anglia, Norwich, UK

本文分析已發表的資訊與個人通訊，試圖探討新熱帶與舊熱帶區兩者的草食性動物相存在明顯差異的原因。與新熱帶區相比，舊熱帶區擁有較多生物量的大型草食性動物，原因與具有較低多樣性的小型草食性動物、不同的原住民狩獵方式、較大的樹棲性脊椎動物、較大的果實、花與果的時空分布情形或其他因素有關。本文結果並不支持新熱帶區雨林在前全新世曾經存在過種類豐富的大型草食動物之說法。作者也不認為兩個熱帶區的動物相差異導因於在新世界區人類活動造成的動物滅絕。

Abstract
Aim
Large herbivores have important effects upon Paleotropical ecosystems, but attain much lower biomass densities in the Neotropics. We assess how this difference in herbivore activity has generated different ecological and evolutionary trajectories in the New and Old World tropics. We also propose an explanation for how the greater biomass density in the Old World came about.
Location
Data were compiled primarily from moist tropical forests, although more of the relevant information to address most of our hypotheses was available from the mainland areas of Africa, Asia, and South America than elsewhere.
Methods
We gleaned data from published information and personal communication. We compared body masses and a variety of other types of information for the New- and Old-World tropics. We proposed that interhemispheric differences exist in a variety of processes, including herbivory, frugivory, and flower visitation. We erected hypotheses and evaluated them qualitatively, and, when information was available, tested them using simple ratios of species in various taxonomic and trophic categories. To make the comparisons more meaningful, we specified appropriate data selection criteria.
Results
A general pattern of differences emerges from this review. Compared with Neotropical forests, the much greater biomass densities of large herbivores in Paleotropical forests are associated with a lesser diversity of small herbivores, different hunting methods used by indigenous humans, larger arboreal vertebrates, larger fruits, different patterns of fruit and flower dispersion in space and time, a lesser abundance of most types of reproductive plant parts, and other features. The existence of a species-rich fauna of large herbivores in the pre-Holocene Neotropical rain forest was not supported.
Main conclusions
The potential for large herbivores to cause functional differences between the New and Old World tropical forests has been virtually unexplored, despite the well-known importance of large herbivores in the Old World tropics. The evaluations of our hypotheses suggest that the abundance of large herbivores in the Old World tropics has launched it onto a different evolutionary trajectory than that of the NewWorld tropics. The relevant evidence, although scanty, suggests that the interhemispheric ecological differences are not an artefact of recent megafaunal extinctions in the New World. Recent human activities have, however, reduced population sizes of large wild herbivores in the Old World, and increased population sizes of livestock. This has likely created a rather homogeneous, anthropogenic selection pressure that tends to erase the evolutionary differences between the two tropical worlds.

早在鱗翅目輻射演化之前促進費洛蒙生成的關鍵性生化合成基因家族便已出現

Key biosynthetic gene subfamily recruited for pheromone production prior to the extensive radiation of Lepidoptera

BMC Evolutionary Biology 2008, 8:270 Full text: PDF (2.4MB)

Marjorie A Liénard¹ , Maria Strandh¹ , Erik Hedenström³ , Tomas Johansson² and Christer Löfstedt¹

¹Chemical Ecology and Ecotoxicology, Department of Ecology, Lund University, Ecology Building, SE-22362, Lund, Sweden ²Microbial Ecology, Department of Ecology, Lund University, Ecology Building, SE-22362, Lund, Sweden ³Department of Natural Sciences, Institute of Natural Sciences, SE-85170, Sundsvall, Sweden

author email corresponding author email

Abstract

Background

Moths have evolved highly successful mating systems, relying on species-specific mixtures of sex pheromone components for long-distance mate communication. Acyl-CoA desaturases are key enzymes in the biosynthesis of these compounds and to a large extent they account for the great diversity of pheromone structures in Lepidoptera. A novel desaturase gene subfamily that displays Δ11 catalytic activities has been highlighted to account for most of the unique pheromone signatures of the taxonomically advanced ditrysian species. To assess the mechanisms driving pheromone evolution, information is needed about the signalling machinery of primitive moths. The currant shoot borer, Lampronia capitella, is the sole reported primitive non-ditrysian moth known to use unsaturated fatty-acid derivatives as sex-pheromone. By combining biochemical and molecular approaches we elucidated the biosynthesis paths of its main pheromone component, the (Z,Z)-9,11-tetradecadien-1-ol and bring new insights into the time point of the recruitment of the key Δ11-desaturase gene subfamily in moth pheromone biosynthesis.

Results

The reconstructed evolutionary tree of desaturases evidenced two ditrysian-specific lineages (the Δ11 and Δ9 (18C>16C)) to have orthologs in the primitive moth L. capitella despite being absent in Diptera and other insect genomes. Four acyl-CoA desaturase cDNAs were isolated from the pheromone gland, three of which are related to Δ9-desaturases whereas the fourth cDNA clusters with Δ11-desaturases. We demonstrated that this transcript (Lca-KPVQ) exclusively accounts for both steps of desaturation involved in pheromone biosynthesis. This enzyme possesses a Z11-desaturase activity that allows transforming the palmitate precursor (C16:0) into (Z)-11-hexadecenoic acid and the (Z)-9-tetradecenoic acid into the conjugated intermediate (Z,Z)-9,11-tetradecadienoic acid.

Conclusion

The involvement of a single Z11-desaturase in pheromone biosynthesis of a non-ditrysian moth species, supports that the duplication event leading to the origin of the Lepidoptera-specific Δ11-desaturase gene subfamily took place before radiation of ditrysian moths and their divergence from other heteroneuran lineages. Our findings uncover that this novel class of enzymes affords complex combinations of unique unsaturated fatty acyl-moieties of variable chain-lengths, regio- and stereo-specificities since early in moth history and contributes a notable innovation in the early evolution of moth-pheromones.

眼紋演化的另類模型與鱗翅目翅紋系列之同源性

Alternative models for the evolution of eyespots and of serial homology on lepidopteran wings. Bioessays 30: 358-366 full article

Monteiro A (2008)

Abstract.
Serial homology is widespread in organismal design, but the origin and individuation of these repeated structures appears to differ with the different types of serial homologues, and remains an intriguing and exciting topic of research. Here I focus on the evolution of the serially repeated eyespots that decorate the margin of the wings of nymphalid butterflies. In this system, unresolved questions relate to the evolutionary steps that lead to the appearance of these serial homologues and how their separate identities evolved. I present and discuss two alternative hypotheses. The first proposes that eyespots first appeared as a row of undifferentiated repeated modules, one per wing compartment, that later become individuated. This individuation allowed eyespots to appear and disappear from specific wing compartments and also allowed eyespots to acquire different morphologies. The second hypothesis proposes that eyespots first appeared as individuated single units, or groups of units, that over evolutionary time were co-opted into new compartments on the wing. I discuss the merits of each of these alternate hypotheses by finding analogies to other systems and propose research avenues for addressing these issues in the future.