photo: Olympic Naturual History Photos

標題：A comparative analysis of the evolution of imperfect mimicry

摘要

Although exceptional examples of adaptation are frequently celebrated, some outcomes of natural selection seem far from perfect. For example, many hoverflies (Diptera: Syrphidae) are harmless (Batesian) mimics of stinging Hymenoptera. However, although some hoverfly species are considered excellent mimics, other species bear only a superficial resemblance to their models and it is unclear why this is so. To evaluate hypotheses that have been put forward to explain interspecific variation in the mimetic fidelity of Palearctic Syrphidae we use a comparative approach. We show that the most plausible explanation is that predators impose less selection for mimetic fidelity on smaller hoverfly species because they are less profitable prey items. In particular, our findings, in combination with previous results, allow us to reject several key hypotheses for imperfect mimicry: first, human ratings of mimetic fidelity are positively correlated with both morphometric measures and avian rankings, indicating that variation in mimetic fidelity is not simply an illusion based on human perception; second, no species of syrphid maps out in multidimensional space as being intermediate in appearance between several different hymenopteran model species, as the multimodel hypothesis requires; and third, we find no evidence for a negative relationship between mimetic fidelity and abundance, which calls into question the kin-selection hypothesis. By contrast, a strong positive relationship between mimetic fidelity and body size supports the relaxed-selection hypothesis, suggesting that reduced predation pressure on less profitable prey species limits the selection for mimetic perfection.

不完美擬態 (imperfect mimicry) 指的是一個擬態物種（以人類觀點）猛一看很像A物種，但仔細端詳後又發現其實不太像，有時又會覺得很像B物種，但又覺得有差異，對人類來說就覺得「擬態的不完美」。這個看似對立於「完美擬態」的現象看似成立，其實存在著很多爭議，像是為什麼要有點不像？不像的部分對擬態也有貢獻？其實擬態兩個以上的物種？關於這些問題的研究產生很多對立的結果，到目前為止並未有一致的結論。

Fig. 1  食蚜蠅的斑紋分析，圓圈代表model，三角形代表mimics，白色代表蜜蜂型，灰色代表胡蜂型。 結果顯示兩型間的相似方向並不重疊。

Fig. 4 斑紋相似度與身體尺寸有強烈的正相關（詳細統計結果見原文）

這篇文章藉由比較性的方法來討論不完美擬態的演化來源。太細節的部分就姑且不談，作者群透過比較食蚜蠅 (hoverfly) 的型態（尺寸、斑紋與不同的接受者）與系統發生學的方式，發現以下幾個有趣的證據：

1. 透過型態的測量與鳥類的觀點來看，以人類的角度來判斷物種是否不完美擬態太過簡化這個現象；

2. 經過分析後發現，本來認為可能是擬態兩個擬態模型的食蚜蠅，其實沒有任何一個物種的斑紋實際上同時涉入兩種以上的擬態環，顯示「擬態多物種假說」值得存疑；

3. 沒有任何證據顯示擬態的精確度與物種豐度有負相關（物種數量越少，擬態的越精確），這可能與親屬選汰 (kin selection) 有關；

4. 擬態的精確度與身體尺寸有強烈的正相關，支持緩和選汰假說 (relaxed-selection hypothesis)，顯示獲益較少的物種受到較少的捕食壓力，影響擬態精確度的選汰。

這個研究以食蚜蠅為例子是因為那實在是不完美擬態的典範，然而這篇文章並非完全解答這個現象，至少就食蚜蠅的總物種數來說，文中討論的物種數比例上不算多，有可能陷入見樹不見林的風險。不完美擬態也廣泛的發生在各種其他類群的昆蟲上，這個研究的論點是基於「不完美擬態是到目前為止的終點」，但更多觀察到的現象讓我們覺得「不完美擬態可能只是完美擬態的過程」，代表不同的類群不同的演化故事，帶來的結論可能大相逕庭。

photo: Hannah Rowland

標題：Masquerade is associated with polyphagy and larval overwintering in Lepidoptera

摘要

Masquerading animals benefit from the difficulty that predators have in differentiating them from the inedible objects, such as twigs, that they resemble. The function of masquerade has been demonstrated, but how it interacts with the life history of organisms has not yet been studied. Here, we report the use of comparative analyses to test hypotheses linking masquerade to life-history parameters.We constructed a phylogenetic tree of the British species of the lepidoptera families Geometridae and Drepanidae, and compiled life history and coloration data from the literature. We found that masquerade is associated with the exploitation of a greater diversity of host plants whether measured by the number of families or genera. We found a positive relationship between body size and polyphagy among masquerading species, and no relationship among cryptic species. Among those species predomi- nantly found on woody host plants, masquerading species are more likely to overwinter as larvae while cryptic species mostly overwinter as pupae. Polyphenism was associated with multivoltinism in masquerading species but not cryptic species. Taken together, our results show that masquerade must be viewed as a strategy distinct to crypsis and hence may provide insights into the evolution of both defensive strategies. Our study further demonstrates the utility of broad-scale between-species comparisons in studying associations between diverse life-history parameters and sensory aspects of predator-prey interactions.

Fig. 1 使用不同策略的尺蛾幼蟲。上左警戒色，上中、上右不同顏色的隱蔽，下排全為偽裝。

「偽裝」(mesquerading) 這個現象就是生物的外觀類似枝條、葉子，對目標捕食者發送我不是食物的訊息，降低被找到的風險。而凡事都有代價，如果要適應這樣的外觀，生活的方式勢必要出現某些演化上的權衡 (trade-off)，生活史或策略產生某些對應的變化，讓這個策略的優勢得以最大化。

這篇文章的作者群想瞭解物種的生活史與偽裝這個策略在演化上的關聯性，建立英國的尺蛾科與鉤蛾科的親緣關係，並將其生活史特徵（食性、棲息位置、年世代數等，見內文table 1）映象至親緣關係上，推測特徵的演化。

Fig. 2 尺蛾與鉤蛾的親緣關係。白線為隱蔽性，藍線為偽裝，黑線為警戒性，虛線為混合策略。

從樹的結構與特徵的推測來看，採用偽裝策略的物種，無論從屬級或科級的角度來看，連結了利用較高的寄主植物多樣性。生活史的分析發現以偽裝策略為主的物種中，身體的尺寸與廣食性是正相關的關係，但在採取隱蔽性的物種則沒有這個關係。而偽裝策略為主的物種大多棲息在木本的植物上，以幼蟲的形式過冬，而隱蔽性的物種則以蛹的形式過冬。多表型性在偽裝的物種中與一年多世代有關聯，但在隱蔽物種中則沒有這個關聯性。總合這全部的結果來看，偽裝策略與隱蔽性策略物種所擁有的生活史與其演化歷史甚有差異，因此應該把這兩種策略視為不同的防禦體系。

Fig. 4 寄主植物的數量與棲息位置的差異。白柱為隱蔽性，斜線為偽裝。

Fig. 3 身體尺寸與寄主屬級數量的關係。圓圈為隱蔽性，方塊為偽裝。

可能看到這有人會覺得很奇怪，為什麼一開始只是討論生態特徵的演化，到最後結論變成偽裝與隱蔽性要視為兩種不同的機制？

這其實有個很長的故事，但先在這說個精簡版。一言蔽之，如果看到像枝條的蟲，一般人想到的是「這像枝條，顏色也像枝條，平常我分不太出來，捕食者也分不出來，所以這是隱蔽也是偽裝」。關於這兩者的定義在30年前已經有人吵過一架（正在整理中，出文時間不確定），但兩者間的確有相似處讓人弄不清楚究竟是「偽裝成落葉」或是「隱蔽於落葉中」之類的問題，這也反應在眾多科普文章常常也沒說明定義，讓受眾也搞不太清楚到底哪個是哪個。既然以前有人起過爭議，就代表兩個概念各有人支持合併或分開，所以這個研究到最後才會去討論這兩者間的特徵起源與生活史演化的差異對應，總結出應該把兩個概念視為不同體系防禦的論述。

Fig. 1 箭毒蛙的親緣關係與將各種特徵映象至樹上，以推測其演趨勢

標題：Aposematism increases acoustic diversification and speciation in poison frogs.
摘要

Multimodal signals facilitate communication with conspecifics during court- ship, but they can also alert eavesdropper predators. Hence, signallers face two pressures: enticing partners to mate and avoiding detection by enemies. Undefended organisms with limited escape abilities are expected to mini- mize predator recognition over mate attraction by limiting or modifying their signalling. Alternatively, organisms with anti-predator mechanisms such as aposematism (i.e. unprofitability signalled by warning cues) might elaborate mating signals as a consequence of reduced predation.We hypoth- esize that calls diversified in association with aposematism. To test this, we assembled a large acoustic signal database for a diurnal lineage of apose- matic and cryptic/non-defended taxa, the poison frogs. First, we showed that aposematic and non-aposematic species share similar extinction rates, and aposematic lineages diversify more and rarely revert to the non- aposematic phenotype. We then characterized mating calls based on morphological (spectral), behavioural/physiological (temporal) and environmental traits. Of these, only spectral and temporal features were associated with aposematism. We propose that with the evolution of anti- predator defences, reduced predation facilitated the diversification of vocal signals, which then became elaborated or showy via sexual selection.

Fig. 2 箭毒蛙的種化分析

Fig. 3 系統發生學上對植物鹼的分泌與顯眼度的回歸分析

photo: NSF

標題：Multilocus species trees show the recent adaptive radiation of the mimetic Heliconius butterflies

摘要

Müllerian mimicry among Neotropical Heliconiini butterflies is an excellent example of natural selection, associated with the diversification of a large continental-scale radiation. Some of the processes driving the evolution of mimicry rings are likely to generate incongruent phylogenetic signals across the assemblage, and thus pose a challenge for systematics. We use a data set of 22 mitochondrial and nuclear markers from 92% of species in the tribe, obtained by Sanger sequencing and de novo assembly of short read data, to re-examine the phylogeny of Heliconiini with both supermatrix and multispecies coalescent approaches, characterize the patterns of conflicting signal, and compare the performance of various methodological approaches to reflect the heterogeneity across the data. Despite the large extent of reticulate signal and strong conflict between markers, nearly identical topologies are consistently recovered by most of the analyses, although the supermatrix approach failed to reflect the underlying variation in the history of individual loci. However, the supermatrix represents a useful approximation where multiple rare species represented by short sequences can be incorporated easily. The first comprehensive, time-calibrated phylogeny of this group is used to test the hypotheses of a diversification rate increase driven by the dramatic environmental changes in the Neotropics over the past 23 myr, or changes caused by diversity-dependent effects on the rate of diversification.We find that the rate of diversification has increased on the branch leading to the presently most species-rich genus Heliconius, but the change occurred gradually and cannot be unequivocally attributed to a specific environmental driver. Our study provides comprehensive comparison of philosophically distinct species tree reconstruction methods and provides insights into the diversification of an important insect radiation in the most biodiverse region of the planet.

說起毒蝶 (Heliconius)的故事，真是怎麼說也說不完，有關研究怎麼做也做不完。（文章也怎麼看都看不完.....）

早在大概二十世紀初的時候，一群研究毒蝶的科學家以當時的分子生物學技術，增幅幾個在粒腺體內的基因，重建毒蝶的演化歷史，終於得到一個長久以來疑問的證據：這些長的很像的毒蝶的親緣關係不是最近緣的，因此得知這些擬態的斑紋都是趨同演化來的。

Beltrán et al (2002) 以四個基因片段為基礎重建的親緣關係，包含25毒蝶屬物種與有關的外群

是不是近緣種這問題很重要嗎？試想，以普通的物種來說，有相似的斑紋或特徵代表牠們可能分類上是同一屬，同一科，或同一目，這個概念暗示相似特徵物種的親緣關係比較接近，很多類群的親緣關係結果也支持這個概念，這稱為系統發生學上的限制 (phylogenetic constrain)。那麼擬態的斑紋這麼像，雖然我們都假設這些斑紋是趨同演化來的，但在沒有證據的情況下，相似性可能來自牠們是近親的的原因也無法排除，直到系統發生學的結果出來後，才發現原來比我們想像的更複雜。

一開始就說，毒蝶的故事說也說不完，舊的議題配上新的技術是可以弄出新梗的。由於早年技術限制的問題，用的基因片段不多，種類也不多，只能看出個大概的輪廓，於是這個作者群重新檢驗毒蝶族 (Heliconiini) 的親緣關係，取樣了92%的物種以及22個基因，再次建立這個系統發生樹，並且輔以定年的資料，深入探討演化的歷史。

Fig. 1 本篇的主要結果，左下角為分化速率，越紅表示分化速率越快。作者同時將某些重要地理事件以紅線與雪花表示，並未與某些特定的節點產生關聯。

大方向的結果沒有改變，長的相似的依然不是姊妹群，分類上的結果支持一些稀有種分類上應該與某些常見種合併。透過這次全面性的取樣，作者群有機會測試兩個假說：毒蝶族的物種多樣性的分化，是因為過去兩千三百萬年的環境變遷，還是因為自身的演化速率的影響。在這個方面有了一個新的結論：整個族到了毒蝶屬的節上，似乎產生適應上的輻射演化 (adaptive radiation)，透過分化速度的分析，發現毒蝶屬的演化速度確實比起其他的節來說快，但這個速度是漸進的而非急速的 (rapid radiation)，而目前作者群無法明確的指出高度的分化是與哪個環境因子有明確的關聯。

毒蝶的故事，看起來還會繼續綿延下去，科學家的奮鬥將永不止息！

photo from BugGuide

標題：The evolution of Batesian mimicry within the North American Asidini (Coleoptera: Tenebrionidae).

摘要

The asidine darkling beetles (Coleoptera: Tenebrionidae: Asidini) are a diverse tribe of flightless tenebrionids found in many arid and sub-arid habitats around the world. The 263 currently described North American species are contained in ten genera, all of which are restricted to the western half of the continent. The Asidini, like all members of the subfamily Pimeliinae, lack defensive glands. Instead, several phenotypic traits occur within the tribe that may help limit predation. These include the contrasting defensive strategies of crypsis, through either background matching or pattern disruption, and Batesian mimicry of the chemically defended genus Eleodes. Dorsal elytral morphology was assessed between 53 North American asidine species and 13 common Eleodes model species using multiple methodologies to assess similarities between species in the two groups that might indicate mimetic relationships. A phylogeny of the North American asidines is used to map the occurrence of differing defensive strategies within the tribe. Crypsis is reconstructed as the ancestral state, with two origins for Batesian mimicry and multiple reversals. The combination of strongly to weakly cryptic species and varying levels of mimetic fidelity to Eleodes model species make the asidines a promising lineage upon which to further explore the evolution of defensive phenotypes.

八種顯示隱蔽色的Pelecyphorus spp photo from Fig. 1

這個研究所說的是北美的一個擬步行蟲科(Tenebrionidae)其下的一個族 Asidini (漠甲亞科，Pimeliinae)的貝氏擬態斑紋的演化，若要瞭解這個文章，要先配合另一篇文章，Phylogenetic revision of the North American Asidini (Coleoptera: Tenebrionidae)來看。這個族共包含263種，所有的種類都缺乏防禦腺體（可能是不會臭），整個族都棲息在乾燥的環境（可能是沙漠或周遭），大部分的種類都看起來像沙子的顏色，但有幾個種看起來像另一類的擬步行蟲 Eleodes spp.，因此作者對於這些看起來擬態的斑紋的演化趨勢有興趣。整體的架構是這樣，作者先發表了整個族的系統發生學，然後才有這篇討論斑紋演化的文章。

photo from Fig. 2 中間、正下方、左下為擬態者Stenomorpha spp. 其餘為擬態模型Eleodes spp.

研究中使用了11個背方的特徵，這些特徵看起來跟Eleodes spp.的擬態是有關聯的，如果是這樣的話，那把這兩類的物種同時放在一個分析矩陣下跑樹的話，兩者應該會跑在一起，而且有可能可以找出哪些特徵讓兩者看起來這麼像。另一方面作者使用這個族的樹，把擬態的特徵映象至樹上，追溯這些斑紋在樹上的變化，就能瞭解演化趨勢。

結果發現支持這兩類看起來想似的主要特徵是「背面不反光」與「顏色斑紋單一」，而整體的演化趨勢來看的話，如同大部分其他的例子，隱蔽色是祖徵，可能與Eleodes spp.的擬態特徵是複數起源。

雖然說擬態起來的相似度還是要從整體的行為斑紋來看，但分別把特徵拆開追溯其演化趨勢，有助於讓我們了解究竟相似度從何而來，也可以為未來更細膩的研究打下基礎。

photo from Heliconius.org

photo from Kronforst Lab

標題：Wing patterning genes and coevolution of Müllerian mimicry in Heliconius butterflies: Support from phylogeography, cophylogeny, and divergence times.

摘要

Examples of long-term coevolution are rare among free-living organisms. Mullerian mimicry in Heliconius butterflies had been suggested as a key example of coevolution by early genetic studies. However, research over the last two decades has been dominated by the idea that the best-studied comimics, H. erato and H. melpomene, did not coevolve at all. Recently sequenced genes associated with wing color pattern phenotype offer a new opportunity to resolve this controversy. Here, we test the hypothesis of coevolution between H. erato and H. melpomene using Bayesian multilocus analysis of five color pattern genes and five neutral genetic markers.We first explore the extent of phylogenetic agreement versus conflict between the different genes. Coevolution is then tested against three aspects of the mimicry diversifications: phylogenetic branching patterns, divergence times, and, for the first time, phylogeographic histories.We show that all three lines of evidence are compatible with strict coevolution of the diverse mimicry wing patterns, contrary to some recent suggestions. Instead, these findings tally with a coevolutionary diversification driven primarily by the ecological force of Mullerian mimicry.

穆氏擬態的毒蝶(Heliconius)就是很像又都有毒，這麼相像的斑紋到底怎麼來的？這是一個很大的疑問。而且，很多人認為兩個物種長的這麼像又分佈在同一個地方，承受一樣的天擇壓力，那麼，這個斑紋應該是共演化(coevolution)的關係吧？

大約十幾年前時有James Mallet有寫文章特別討論過，那個時候特別提到，雖然毒蝶的每個斑紋都很像，但這僅是斑紋上的趨同，不是兩個物種的共演化。然而在這十年間，分子生物技術的發展大量應用在毒蝶擬態的研究上，無論是控制斑紋的基因，或是與種化有關的基因都被找出來了，如果重新檢視有沒有共演化這個問題，會不會不一樣呢？

於是H. erato 與H. melpomene這兩個經典的穆氏擬態分類群又上場了。作者利用了五個控制斑紋的基因 (optix, bves, kinesin, GPCR, and VanGogh)跟五個中性基因 (COI and COII, plus four nuclear genes: SUMO, Suz12, 2654, and CAT)再次重建親緣關係。作者透過比較兩個物種的親緣關係的樹型、分化的時間與生物地理的演化歷史，重新分析這兩個物種的演化歷史。結果發現這兩個物種在這三方面的分析中都支持兩者間的共演化關係，樹型相似、斑紋分化時間相似，生物地理的分析也相關，這個結果似乎提供了一個與之前完全相反的證據，支持新熱帶蝴蝶的擬態斑紋的共演化。

這個文章有另一個值得討論的地方，以前總認為控制擬態的斑紋，或是說明顯受到天擇/性擇的基因，是不能用來重建物種的親緣關係，因為會有無法正確反應物種演化歷程的疑慮，因此總是會選擇被天擇/性擇影響比較小，比較「中性」的基因來重建親緣關係，可是這個文章用了應該明顯受到天擇影響的基因，反而呈現了完全不同的理論與故事，這給研究演化的科學家們一個新的思考方向，或許使用以前不被考慮的基因，更能反應該性狀的演化歷程。

photo from Cleridae (wiki)

標題：Aposematism and mimicry in soft-bodied beetles of the superfamily Cleroidea (Insecta)

摘要

The evolution of animal life strategies is among the main themes of current evolutionary biology. Checkered beetles, soft-winged flower beetles and their allies (superfamily Cleroidea), exhibit well-known aposematic colour patterns, particularly in the family Cleridae, which participate in mimicry complexes mostly with unpalatable beetles, ants and velvet ants representing a Mullerian–Batesian continuum. Many cleroids also exhibit attenuated hardening of cuticular layers resulting in a soft-bodied appearance. Here, a molecular phylogenetic analysis of the entire Cleroidea was performed using sequences of two nuclear and two mitochondrial loci of ~4 kb total length. Inferred phylogenies were used to reconstruct ancestral colour patterns and involvement in mimicry complexes. The hypothesis of a soft-bodied ancestor of Cleridae and allies was tested. The phylogenetic analyses corroborated the expanded Cleroidea concept including Byturidae and Biphyllidae formerly classified as Cucujoidea. Character state optimization showed cryptic col- oration was the ancestral state in Cleroidea, from which aposematic coloration originated several times in distant cleroid lineages. Within Cleridae, mimicry also arose from an ancestor that was cryptic, and multiple lineages that mimicked unpalatable beetles (Chrysomelidae, Meloidae, Lycidae) and stinging Hymenoptera evolved. Aposematic coloration was acquired in all major clerid lineages including Thanerocleridae, which are either the sister group of Chaetosomatidae or Cleridae. These findings suggest that mimetic traits in the clerid clade evolved at various times, possibly soon after the origin of soft-bodiedness. The adaptive value of aposematism in cleroids is likely to be enhanced in soft-bodied species, as this trait provides limited means of protection against predators, and therefore may promote the acquisition of aposematic and mimetic col- oration in various ecological situations.

郭公蟲 (Cleroids)是鞘翅目下的一個總科，全球約有3000種，從訪花到食腐肉的食性都有，有的郭公蟲還是飼料害蟲（如赤足郭公蟲）。這類群的外觀有的看起來像菊虎，有的看起來像葉蚤，有的看起來像螞蟻，說白了就是一個到處複製其物種斑紋的類群，可是這樣的斑紋演化是怎麼來的，其祖先是隱蔽色還是原本就有這些警戒色呢？郭公蟲的身體有硬有軟，這些硬的類群跟軟的類群各自獨立演化，或者這是一個各種不同的衍徵呢？

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作者用了兩個核基因（18S 與 28S的D2區域）與兩個粒線體基因（16S與cox1），大約4kb的長度來重建郭公蟲總科的親緣關係。細部的分類就不談了，特徵追溯的結果顯示郭公蟲總科的體色的祖徵應該是隱蔽色（82％），擬態螞蟻或其他甲蟲的特徵都是各自演化出來的。而軟/硬身體的類群則顯示郭公蟲總科的祖徵的身體是硬的而且有的是隱蔽色（97％）。這個演化關係似乎暗示軟身體的那群與演化出警戒色/擬態的關係比較緊密（軟身體群比較多與警戒色/擬態的類群），或許是因為身體柔軟受到捕食者（也就是天擇）的影響比較大，因此演化的方向朝著留下具有警戒色/擬態的類群。

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現在推測特徵演化大部分用MCMC的參數模型，這個研究也是，對於這個模型的使用沒什麼太大的意見，甚至可以說這種變動式的模型更適合計算演化特徵的改變，只是說這種方法算出來後，各個節上所呈現的是機率，這該如何解釋呢？該說那個共祖有x%的機會是A特徵，(1-x%)的機會是B特徵嗎？可是學生態的人很難理解這點，因為野外看到的特徵就是100%是某樣子（我這裡所說的不是野外族群的比例，那是另一個計算法了），不會因為時空背景有差異（有誰可以說說5%的機率看到某支蟲是紅色實際上應該是怎樣？一直在亂數閃爍嗎？）

我想，這就是薛丁格的貓吧。

Wing-pattern mimicry in butterflies has provided an important example of adaptation since Charles Darwin and Alfred Russell Wallace proposed evolution by natural selection .150 years ago. The neotropical butterfly genus Heliconius played a central role in the development of mimicry theory and has since been studied extensively in the context of ecology and population biology, behavior, and mimicry genetics. Heliconius species are notable for their diverse color patterns, and previous crossing experiments revealed that much of this variation is controlled by a small number of large-effect, Mendelian switch loci. Recent comparative analyses have shown that the same switch loci control wing-pattern diversity throughout the genus, and a number of these have now been positionally cloned. Using a combination of comparative genetic mapping, association tests, and gene expression analyses, variation in red wing patterning throughout Heliconius has been traced back to the action of the transcription factor optix. Similarly, the signaling ligand WntA has been shown to control variation in melanin patterning across Heliconius and other butterflies. Our understanding of the molecular basis of Heliconius mimicry is now providing important insights into a variety of additional evolutionary phenomena, including the origin of supergenes, the interplay between constraint and evolvability, the genetic basis of convergence, the potential for introgression to facilitate adaptation, the mechanisms of hybrid speciation in animals, and the process of ecological speciation.

摘要 [原文網址]

The mimetic butterflies Heliconius erato and Heliconius melpomene have undergone parallel radiations to form a near-identical patchwork of over 20 different wing-pattern races across the Neotropics. Previous molecular phylogenetic work on these radiations has suggested that similar but geographically disjunct color patterns arose multiple times independently in each species. The neutral markers used in these studies, however, can move freely across color pattern boundaries, and therefore might not represent the history of the adaptive traits as accurately as markers linked to color pattern genes. To assess the evolutionary histories across different loci, we compared relationships among races within H. erato and within H. melpomene using a series of unlinked genes, genes linked to color pattern loci, and optix, a gene recently shown to control red color-pattern variation. We found that although unlinked genes partition populations by geographic region,optix had a different history, structuring lineages by red color patterns and supporting a single origin of red-rayed patterns within each species. Genes closely linked (80–250 kb) to optix exhibited only weak associations with color pattern. This study empirically demonstrates the necessity of examining phenotype-determining genomic regions to understand the history of adaptive change in rapidly radiating lineages. With these refined relationships, we resolve a long-standing debate about the origins of the races within each species, supporting the hypothesis that the red-rayed Amazonian pattern evolved recently and expanded, causing disjunctions of more ancestral patterns.

在系統發生學中，如果我們想要知道一個特徵的演化起源，也就是大家最想看的「怎麼演化」，通常會有個樹，上面有很多顏色很漂亮，然後你追著那個你想看的顏色，就會知道這個特徵發生了幾次，然後你在看圖說故事（譬如多年前有人探討竹節蟲翅的演化來源一樣）。重點就在於通常我們重建一棵樹的時候，理論告訴我們要選中性或偏中性的分子標記，不能選那些受到強烈天擇作用的標記，這樣才能純粹的反應物種間的關係，然後再用你想看的特徵去追溯，才會知道演化的來源。

而這如果用在擬態的演化這件事上會怎樣？通常你會看到不同擬態樣子的物種混在同一個支系裡，然後你用這個樹去追溯擬態的特徵，九成九會告訴你「所有的擬態特徵都是每個物種獨立演化多次來的」，所以哪個特徵先出現會變得模糊不清，原因就在於這些中性的分子標記是可以在各個物種間傳來傳去的，不一定會跟著強烈天擇的翅紋走，因此基於這些標記重建的樹無法反應擬態特徵的演化歷史。

所以為了知道這個特徵的演化來源與方向，這篇文章就用了控制斑紋的基因重建親緣關係，結果發現不同物種間但同樣斑紋的種類親緣關係較近，也就是在分子的層級上，擁有相同擬態翅紋的物種是趨同的，這就可以用來解釋很多事情，像是提供穆氏擬態的演化假說證據（註）等等。

當然要做到這個層級的前提有很多，像是要先知道各個控制斑紋的基因是哪個，先花大錢把序列全部定出來，實驗動物本身要能夠雜交容易飼養繁殖等等，相較於其他地區的擬態群來說，毒蝶提供很多這類的優勢，自然是個很好的模式動物。

註：穆氏擬態的演化假說是不同物種間的斑紋會越來越像，以求達最適化。

原文標題：Evolution of mimicry patterns in Metriorrhynchus (Coleoptera: Lycidae): The history of dispersal and speciation in Southeast Asia

摘要 [原文網址]

The concept of Müllerian mimicry suggests convergent evolution to an intermediate pattern and does not predict polymorphism in mimicry rings. We examined the evolution of mimicry patterns and the order of divergence of various factors, including the role of aposematic patterns in speciation, in a clade of net-winged beetles with a robust phylogeny that suggests that they dispersed from the Australian to Asian plate. We found strong evidence for the evolution of mimicry via advergence inMetriorrhynchus because older patterns are represented in the Oriental region within more than 100 species of lycids from several lineages. Advergence was likely the cause of the observed intraspecific polymorphism in contrast to the predicted universal monomorphism. Polymorphism was found in populations of two species in Sumatra and Borneo and in populations fine-tuned to subtle variants in various habitats. The advergence is likely to be based on the small population sizes of immigrants. The differences in population sizes result in much higher benefits for dispersing species than native populations. Speciation was trigged by the divergence in aposematic coloration, and the genetic differences accumulated slowly during incomplete isolation. We assumed that the differentiation in genitalia through sexual selection ultimately reinforced speciation initiated by the shift between mimicry patterns.

紅螢是個全世界分布的東西，主要分布在熱帶與亞熱帶，很多的觀察都指出紅螢似乎是個很有用的樣式，諸如一些鱗翅目（如榕蛾）、半翅目（某些星椿）與鞘翅目（如蓬萊紅天牛、金花蟲），都可以看到像是紅螢的影子。紅螢的防禦來自於自體分泌的吡嗪類化合物（pyrazines)與紅螢酸（lycidic acid），這類物質對於大部分的捕食者而言是很有效的避忌物。

這篇文章主要就是在討論紅螢科Metriorrhynchus屬的擬態斑紋的演化，配合生物地理事件加上定年，就可以知道每個節上發生的地理事件，然後利用這些資料推斷擬態的斑紋是否促進種化與限制了分布。這個屬主要的斑紋如下圖，擬態的斑紋就是只1.2/3.4這兩種中段是紅尾段是藍的樣式。利用了系統發生學的方法與定年後，發現擬態的種與其姊妹種（如3.4/5）的遺傳差距其實不高，顯示擬態的斑紋可能促進了族群的分化，而不同區域的擬態群可能來自多態型的分化。



其實這樣的介紹有點太簡單，只把一些比較重要的重點節錄出來，文內討論了種化、斑紋演化、生殖器構造等等，用了很多不同的面象討論這個屬的種化歷程，若要了解的更詳細，還是請看內文吧！

Until recently, the study of negative and antagonistic interactions (for example, competition and predation) has dominated our understanding of community structure, maintenance and assembly¹. Nevertheless, a recent theoretical model suggests that positive interactions (for example, mutualisms) may counterbalance competition, facilitating long-term coexistence even among ecologically undifferentiated species². Müllerian mimics are mutualists that share the costs of predator education³ and are therefore ideally suited for the investigation of positive and negative interactions in community dynamics. The sole empirical test of this model in a Müllerian mimetic community supports the prediction that positive interactions outweigh the negative effects of spatial overlap⁴ (without quantifying resource acquisition). Understanding the role of trophic niche partitioning in facilitating the evolution and stability of Müllerian mimetic communities is now of critical importance, but has yet to be formally investigated. Here we show that resource partitioning and phylogeny determine community structure and outweigh the positive effects of Müllerian mimicry in a species-rich group of neotropical catfishes. From multiple, independent reproductively isolated allopatric communities displaying convergently evolved colour patterns, 92% consist of species that do not compete for resources. Significant differences in phylogenetically conserved traits (snout morphology and body size) were consistently linked to trait-specific resource acquisition. Thus, we report the first evidence, to our knowledge, that competition for trophic resources and phylogeny are pivotal factors in the stable evolution of Müllerian mimicry rings. More generally, our work demonstrates that competition for resources is likely to have a dominant role in the structuring of communities that are simultaneously subject to the effects of both positive and negative interactions.