這是什麼啊? 可以吃嗎?

雄性擇偶的條件是如何判斷的？

2011-09-01T11:40:00.006+08:00

[image]
Iserbyt A, Gossum HV. 2011. your true colour: cues for male mate preference in an intra-specific mimicry system. Ecological Entomology. DOI: 10.1111/j.1365-2311.2011.01300.x [full text]
Li CC, Hsiao WF. 2008. The Reproductive Strategy of Ischmura senegalensis (Ramhttp://www.blogger.com/img/blank.gifbur) (Odonata: Coenagrionidae). Taiwan insect. 28: 57-65. [Abstract]

物種的多態型大多出現在雌性個體，並且為了增加交配機會而存在，但也易受捕食壓力而限制，而部份雌性的多態型是以擬態同種雄性表型的方式存在，有研究指出其用意為防止雄性的騷擾，例如Ischnura senegalensis雌性除了正常之橘色型成蟲外，在性成熟前期具有綠色型之malemimic，但有研究顯示雌綠型仍具有最高的交配率，故其擬態用途仍有待後續研究討論(Li & Hsiao 2008)。在此，Iserbyt及Gossum也以Nehalennia Irene於野外及實驗室內進行研究，將雄性的反應行為分成 (a)無反應 (b)飛離 (c)有接觸 (d)嘗試交配四種，再經由人為控制色彩去比較雄性個體對於 (a) gynomorph (b) male (c) models的選擇偏好差異，結果發現：顏色改變並不影響雄性偏好(andromorph > male > gynomorph)，因此雌蟲體色並非影響交配行為的主要原因。

為何車前燈蛾的翅紋多樣性可以長期存在？

2011-08-26T15:29:00.004+08:00

[image]
Nokelainen O, Hegna RH, Reudler JH, Lindstedt C, Mappes J. 2011. Trade-off between warning signal efficacy and mating success in the wood tiger moth. Proc. R. Soc. B. doi: 10.1098/rspb.2011.0880 [full text]

從演化的觀點來看，特徵選汰應傾向於對物種存活有利的方式，並且，後期這些基因特質應達到穩定且妨礙多態型的存在，但有許多警戒色的例子顯示多態型的物種是可以同時存在於相同族群中，其顯示不同型態之特徵可能具有不同優勢存在，或其可能具有相同功效。在此，作者以具有明顯翅紋變異的白色及黃色車前燈蛾(Parasemia plantaginis)作為獵物，以藍山雀(Parus caeruleus)作為捕食者測試翅紋警戒色在存活率和繁殖成功率之間的關係。結果顯示：(a)捕食者對於黃色翅紋有較長的攻擊延遲時間 (b)黃色翅紋的個體存活率比白色翅紋的個體好 (c)白色翅紋的個體繁殖成功率比黃色翅紋個體好，因此，作者認為此結果正好為車前燈蛾白色及黃色翅紋同時共存於自然界作一個很好的解釋。

毒蛺蝶的共域多態性擬態乃經由染色體重組維繫

2011-08-18T11:19:00.003+08:00

文獻來源: Joron et al. (2011) Chromosomal rearrangements maintain a polymorphic supergene controlling butterfly mimicry. Nature doi:10.1038/nature10341

Abstract
Supergenes are tight clusters of loci that facilitate the co-segregation of adaptive variation, providing integrated control of complex adaptive phenotypes. Polymorphic supergenes, in which specific combinations of traits are maintained within a single population, were first described for ‘pin’ and ‘thrum’ floral types in Primula and Fagopyrum, but classic examples are also found in insect mimicry and snail morphology. Understanding the evolutionary mechanisms that generate these co-adapted gene sets, as well as the mode of limiting the production of unfit recombinant forms, remains a substantial challenge. Here we show that individual wing-pattern morphs in the polymorphic mimetic butterfly Heliconius numata are associated with different genomic rearrangements at the supergene locus P. These rearrangements tighten the genetic linkage between at least two colour-pattern loci that are known to recombine in closely related species, with complete suppression of recombination being observed in experimental crosses across a 400-kilobase interval containing at least 18 genes. In natural populations, notable patterns of linkage disequilibrium (LD) are observed across the entire P region. The resulting divergent haplotype clades and inversion breakpoints are found in complete association with wing-pattern morphs. Our results indicate that allelic combinations at known wing-patterning loci have become locked together in a polymorphic rearrangement at the P locus, forming a supergene that acts as a simple switch between complex adaptive phenotypes found in sympatry. These findings highlight how genomic rearrangements can have a central role in the coexistence of adaptive phenotypes involving several genes acting in concert, by locally limiting recombination and gene flow.

眼紋的禦敵功能到底是什麼?

2011-07-28T17:27:00.004+08:00

Vallin A, Dimitrova M, Kodandaramaiah U, Merilaita S. (2011) Deflective effect and the effect of prey detectability on anti-predator function of eyespots. Behav Ecol Sociobiol. 65:1629–1636. DOI 10.1007/s00265-011-1173-7[full text]

同心圓的眼紋一般被學者認為是具有禦敵的功能，並於早期實驗得知其具有威嚇天敵的作用，但近期研究發現，眼紋威嚇天敵的作用並非來自於形狀與眼睛相似，而是對比、顯眼性等因素，但眼紋於自然界中仍為十分常見的存在方式，因此作者試圖了解眼紋存在的理由。作者以藍山雀(Cyanistes caeruleus)作為捕食者，以三角型的紙片製成人工獵物(b × h: 30×15 mm2)，再控制獵物的眼紋的大小、數量(0、1、2)和背景差異(以27×21 cm紙板改變獵物背景色)，總共分成兩個實驗，去看不同獵物對捕食者反應的影響。結果顯示：(a) 小眼紋比大眼紋易受到攻擊 (b)獵物和背景的突出程度會比眼紋大小更具影響力 (c) 捕食者的迴避行為在成對眼紋時會比無眼紋好 (d) 威嚇作用只出現在隱避性背景的部分 (e) 眼紋大小和單一大眼紋及無眼紋間無顯著差異。所以總結實驗結果，作者認為影響眼紋功能的主要因子是眼紋和背景的差異度，但天敵的攻擊行為會偏好小型眼紋，表示對天敵為小型的雀形目物種的獵物而言，天敵會攻擊眼紋而避免攻擊獵物本身的重要部位。

耗能低的偽裝也可以很有效嗎？

2011-07-14T16:29:00.008+08:00

Pekár S, Jarab M. (2011) Assessment of color and behavioral resemblance to models by inaccurate myrmecomorphic spiders (Araneae). Invertebrate Biology 130: 83-90. DOI: 10.1111/j.1744-7410.2010.00217.x

依擬態的相似程度，可以將擬態區分成完美擬態和不完美擬態，並且大多數學者認為演化會趨向於完美擬態，不完美擬態則為一個中間過程而已，但在自然界中，不完美擬態的物種數及個體數常遠超過完美擬態的數量，作者認為不完美擬態是針對特定捕食者而演化出的最佳方式，只要把握關鍵的辨識特徵即可，不用浪費多餘的能量去完全擬態，就能達到提高存活率的效果，而蜘蛛被認為具有擬蟻現象(myrmecomorphy)，會擬態單一種或數種螞蟻的色彩，因此，作者以Liophrurillus flavitarsis、Phrurolithus festivus和Micaria sociabilis三種蜘蛛及它們的被擬態者(Aphaenogaster senilis、Lasius platythorax、Liometopum microcephalum)進行研究，探討不完美擬態於演化上存在的假說。作者發現：(a)三種model和各自的mimic間是有共域的 (b)mimic的數量遠低於model (c)擬態者會以擬態行為來加強外型擬態的精確性 (d)不完美擬態的關係會優於完美擬態。

偽裝有利於存活的先決條件是什麼?

2011-06-29T10:40:00.003+08:00

[image Selenia dentaria][image Prunus spinosa]
Skelhorn J, Ruxton GD. (2011) Context-dependent misclassification of masquerading prey. Evol Ecol. 25:751–761. DOI 10.1007/s10682-010-9435-9

部份的物種會以改變自己的外觀或行為等方式達到隱蔽的作用，而這些方式稱為偽裝，並且相較於正常獵物，無經驗的捕食者較不容易發現偽裝的獵物。在此，作者以小雞作為捕食者，以Selenia dentaria作為偽裝的獵物，其幼蟲被認為有偽裝寄主植物(Prunus spinosa)的能力，再 (1)改變樹枝背景使獵物顯眼性產生差異 (2)改變獵物和枝條的量，結果顯示，當獵物數較多且和背景相比較突出時，對有經驗的捕食者而言是最有利的；在與背景相比，顯眼性差的獵物其捕食者攻擊延遲的時間也比較久。因此，作者認為結果顯示偽裝可能要付出代價，且捕食者的決定可能是相當複雜而受多因子影響的。

掠食者的保守食性使得稀少且醒目的獵物得以生存

2011-06-24T11:56:00.003+08:00

Marples NM, Mappes J. (2011) Can the dietary conservatism of predators compensate for positive frequency dependent selection against rare, conspicuous prey? Evol Ecol. 25:737–749. DOI: 10.1007/s10682-010-9434-x

簡介
由於顯眼性色彩容易吸引天敵的注意，警戒色在演化初期對獵物來說是不利且少見的，但若長期只供給相同獵物時，此獵物顯眼性表型中的anti-apostatic個體將被選汰出來。因此，作者以大山雀作為捕食者，杏仁作為人工獵物，測試於隱蔽獵物中19代顯眼性個體和捕食者的捕食行為之關係。結果發現，顯眼性獵物在初級的被攻擊率最高，使具警戒功能的顯眼性個體無法存活，但期捕食者有17隻(24%)會拒決捕食顯眼性獵物。因此，顯眼性獵物要在隱蔽族群中存活是困難的，但在捕食者的捕食行為篩選下，會促使警戒色在演化中被保存。

演化的軍備競賽─紅皇后與有性生殖

2011-06-19T15:40:00.004+08:00

程樹德(2010) 紅皇后與有性生殖。PanScience。http://pansci.tw/archives/3745

作者於短短的一文中敘述了幾件事：
a. 范華倫(Leigh van Valen)於化石堆中悟出”紅皇后假設”：「表示物種必須不斷演化，才能在競爭中保持現有地位，不致於被競爭者淘汰」
b. 有性生殖的優勢在於造成個體基因的重新排列組合，使族群位於不斷變動的環境中有存活下來的機會，或者也能藉此刪除因突變而產生的壞基因；反之，無性生殖無法去除壞基因，甚至可能將其累積，而此稱為穆勒撐高機(Muller’s ratchet)理論。
c. 彩票理論(lottery principle)：無性生殖如同購買大量同號碼的彩票，而有性生殖如同買少量但號碼均不同的彩票，兩者相比時，前者中獎的獲益較高，但是後者中獎的機率則比前者高。
d. 一個共同研究，以病毒與細菌的共同演化實驗表明：兩物種在共演化下，其演化速率會比單獨演化要來得快，此結果則支持范華倫的軍備競賽假說。

總結：自然界的物種多以共演化的方式進行軍備競賽，而有性生殖則為其中一種使族群於競賽中增加存活機會的方式。

環境背景和掠食者的覓食行為有什麼關係？

2011-06-19T14:35:00.006+08:00

[圖片來源: http://online-field-guide.com/Chaunusmarinus.htm]

González-Bernal E, Brown GP, Cabrera-Guzmán E & Shine R. (2011) Foraging tactics of an ambush predator: the effects of substrate attributes on prey availability and predator feeding success. Behav. Ecol. Sociobiol. 65: 1367-1375. DOI: 10.1007/s00265-011-1147-9

掠食者在覓食時會挑選適合埋伏的地點，例如甘蔗蟾蜍(Rhinella marina)會選擇在有人工光源的開擴地覓食。作者將實驗分成兩部份：首先，野外實驗將橡膠墊(1.5×1.5 m)置於野外光源下的地面進行實驗，看在不改變墊子數量、大小及獵物種類之下，不同色彩(黑色和白色)及紋路(光滑和粗糙)之間對捕食行為的影響，結果發現蟾蜍偏好白色粗糙的墊子；另外，作者也進行室內實驗去控制獵物的色彩，發現 (1)白色背景下，捕食者便於搜尋深色獵物 (2)粗糙背景時，獵物的移動速度也會降低。因此，動物的覓食行為，不單只受獵物密度影響，也會受覓食環境的影響。

捕食者對車前燈蛾(Parasemia plantaginis)翅紋警戒色之方向性選擇及強度

2011-04-14T15:29:00.007+08:00

Lindstedt C, Eager H, Ihalainen E, Kahilainen A, Stevens M, Mappesa J. (2011) Direction and strength of selection by predators for the color of the aposematic wood tiger moth. Behav. Ecol. doi:10.1093/beheco/arr017[full text]

簡介
在本篇研究中，作者以Parasemia plantaginis的雌性作為顯眼性獵物，該物種具有雌性多態型(紅/橘/黃三種翅紋色彩)，以Galleria sp.作為隱蔽性獵物，並以pied flycatchers及Great tits作為捕食者進行了四個實驗：
(a) 同時提供顯眼性與隱蔽性獵物，去看在不同獵物下，捕食者的攻擊行為是否有差異；
(b)針對Para. plantaginis翅紋的差異及實驗背景，去進行色彩及亮度的標定，再去比較捕食者視神經的接收比率、製成模型比較；
(c)以兩種不同翅紋的Para. plantaginis去探討捕食者迴避學習的程度差異；
(d)於野外實驗探討捕食者對顯眼性獵物和隱蔽性獵物存活率的影響，以及紅色及橘色顯眼性獵物存活率上的差異。
結果發現：具警戒的顯眼性獵物較具有存活優勢，並且高度的對比色可以加快捕食者的迴避學習，但由於Para. plantaginis本身的化學防禦性物質的影響，使Para. plantaginis的雌性多態型於演化中得以保存，但本研究中所有數據於統計上均無顯著差異存在。

擬態的多種模式：偽裝的多態型會為隱避種帶來更多優勢

2011-03-08T15:32:00.004+08:00

[ 圖片來源]

Skelhorn J & Ruxton GD. (2010) Mimicking multiple models: polyphenetic masqueraders gain additional benefits from crypsis. Behav. Ecol. 22: 60–65. doi:10.1093/beheco/arq166 [full text]

許多生物會藉由擬態無生命的物體來躲避天敵的攻擊，這個現象稱為偽裝(masquerade)。但偽裝的優勢會依被模仿者的數量和偽裝者的比例不同而不同，因此，當物種同時具有不同的多態型時可能是最有利的存在方式，例如：美國胡椒蛾(Biston betularia cognataria)幼蟲就是具有多態型的物種，其幼蟲取食樺木(birch trees)的會像樺木枝條，取食柳樹(willow trees)的就會長得像柳樹枝條。在此作者認為此幼蟲於不同寄主上所呈現的多態型是一種擬態行為，因此，作者以100隻小雞(Gallus gallus domesticus)作為捕食者，以120 *50*50 cm的籠子飼養，控制日照長度及溫度，並以黃粉蟲(Tenebrio molitor) 每天餵養兩次，以四齡的胡椒蛾幼蟲作為獵物，以樺木及柳葉飼養使幼蟲形成棕褐色及綠色兩種不同型式的幼蟲再進行實驗，實驗結果表明：捕食者會將幼蟲誤判為寄主枝條進而產生不捕食行為，但鳥類的行為可能是幼蟲本身的隱避色而非擬態，因此作者又測試了幼蟲的擬態是否成立，發現當幼蟲位於與自己相似的寄主上時，擬態效果是較為顯著的。同時，作者認為此研究也是首次說明物種的多態型對偽裝來說是有利的，並且有利於物種的隱避行為。

當不可食的獵物越多時，是否會分散捕食風險?

2011-01-20T14:54:00.006+08:00

[圖片來源]

Rowland HM, Wiley E, Ruxton GD, Mappes J & Speed MP. (2010) When more is less: the fitness consequences of predators attacking more unpalatable prey when more are presented. Biol. Lett. 6: 732-735. doi: 10.1098/rsbl.2010.0207 [Full text]

1879年，Fritz Müller提出：在擬態行為中，當具警戒信號的獵物比例增加時，獵物的被捕食風險將會降低，因此作者以110隻雄性小雞(Gallus gallus domesticus)作為捕食者，以麵包屑加水作為人工獵物，以chloroquine phosphate作為苦味劑，並且將人工獵物進行染色，可食的(edible)為綠色，不可食的(unpalatable)為紅色，再改變不可食人工獵物的數量，檢示當不可食獵物增加時是否改變捕食風險。結果發現，當不可食獵物數量增加時(總獵物量增加)，捕食者攻擊不可食獵物的次數也增加，因此不可食獵物的數量會下降，但捕食量並未改變，所以捕食風險的降低是由於獵物量增加所造成，但不可食獵物的死亡率會隨攻擊次數而逐漸降低(代表捕食者具有將色彩及味道進行關聯的學習能力)，因此作者認為在自然界中當不可食獵物增加時，並不會分散捕食風險，而是因為總族群量增加使個體被捕食風險降低。

眼紋真的可以嚇到天敵嗎？

2010-12-09T14:47:00.008+08:00

Vallin A, Jakobsson S & Wiklund C.(2010) Constant eyespot display as a primary defense - survival of male and female emperor moths when attacked by blue tits. 43:9-17.

蝴蝶和蛾類在翅膀上常有大型且突出的眼紋(eyespots)，可以用來防止捕食者的攻擊，早期的研究主要著重在鱗翅目眼紋的突然暴露如何干擾捕食者的議題，在此則以探討鱗翅目眼紋長期暴露的潛在效益。作者以兩種本身有共域狀態的物種：天蠶蛾(Saturnia pavonia)作為獵物，藍山雀(Cyanistes caeruleus)作為捕食者於Tovetorp Zoological Research Station進行實驗，並計錄放置獵物後30分鐘內捕食者的行為，發現為有眼紋的蛾類比無眼紋者容易受到攻擊，而認為鳥並未受到眼紋的驚嚇，但也發現體型較大的雌性蛾類個體和體型較小的雌性個體相比是不容易受到攻擊的，所以獵物可能是以體型大小來驚嚇捕食者，因此作者認為天蠶蛾長時間暴露眼紋的行為會對捕食者造成吸引而非驚嚇。

無翅紅蝽警戒色對捕食者的影響

2010-08-23T10:55:00.005+08:00

文獻出處：
Exnerová, A., Svádová, K., Štys, P., Barcalová, S., Landová, E., Prokopová, M., Fuchs, R. & Socha, R. (2006) Importance of colour in the reaction of passerine predators to aposematic prey: experiments with mutants of Pyrrhocoris apterus (Heteroptera). Biological Journal of the Linnean Society 88: 143-153. [Full text]
Prokopová, M., Veselý, P., Fuchs, R. & Zrzavý, J. (2010) The role of size and colour pattern in protection of developmental stages of the red firebug (Pyrrhocoris apterus) against avian predators. Biological Journal of the Linnean Society 100(4): 890–898. [Abstract]

無翅紅蝽(Pyrrhocoris apterus)是半翅目(Hemiptera)昆蟲綱(Insecta)的物種，成蟲體長9-13 mm，發育過程中有五次蛻皮，可以借由蛻皮改變身上的斑紋，體色也可能隨著溫度變化而有些許改變。Alice Exnerová et al. (2006)於1999年至2002年間進行測試，探討無翅紅蝽警戒色的持久性問題、體色和背景色效應的關係，以及體色多態型的起源和警戒色的維持，他以大山雀(Parus major), 藍山雀(Cyanistes caeruleus), 歐亞鴝(Erithacus rubecula)和黑冠鶯(Sylvia atricapilla)作為捕食者，並且實驗過程中所使用的所有物種均於實驗前(一年內)捕獲，再經人工飼養而來。其結果得知，顏色的多態性可以說明：物種的演化是經由隱性突變所造成。

另外，無翅紅蝽成蟲和幼蟲雖然都具有紅色及黑色的體色，但體形大小、色彩和紋路相異，被捕食的頻率則有所差異。Milena Prokopová et al. (2010)假設體型大小會影響捕食者光化學信號的傳遞，而以大山雀(Parus major)和藍山雀(Cyanistes caeruleus)這兩種生態性相似的物種做為捕食者，來探討體型大小不同的鳥類，對無翅紅蝽的體型比例、顏色模式和捕食訊號之間關係的影響。結果顯示捕食者第一次遇到紅蝽時，體型不影響攻擊；但多次後，體型小的獵物較容易被攻擊、取食，並且獵物對兩種捕食者的保護信號有所不同(化學及光學信號)，就連色彩模式也影響捕食者的意願，所以雖然幼蟲和成蟲同時具有紅色和黑色外表，但幼蟲的色彩並沒有提供良好的保護作用。

鳥類能夠學習用不適口度做為獵物有毒程度的訊號

2010-02-17T12:31:00.001+08:00

photo from http://www.tamstuart.com/

Source: Skelhorn J. & Rowe C. (2010) Birds learn to use distastefulness as a signal of toxicity. Proc. R. Soc. B. (in press) [abstract]

具有警戒色的獵物展示顯眼的體色用以警告它們的捕食者其不適口度，並且讓捕食者迅速的學習避免再度攻擊同類的獵物。雖然這樣的機制能夠有效的讓捕食者學習避免捕食，但卻沒有讓捕食者知道到底獵物有多不好吃，而這牽扯到如何能將不適口度較低的獵物包含在捕食者的飲食內，並在這樣的獵物中取得最大能量與生理上抵抗其毒性間取得平衡。因此，捕食者應該要能夠判斷這些受保護的獵物中的毒性高低。在本篇文章的實驗中，作者使用歐洲椋鳥(European starling)做為捕食者，並且測得其能夠利用苦味的程度預測該個體體內含毒的程度，並且使用這樣的資訊進一步選擇毒性較低的獵物，以增加自身取得能量的最大值。本篇的結果支持苦味是一種能夠反應毒性的訊號，並且能夠解釋為何大多數的毒物皆具有苦味。而這個結果也提供了未來若要使用函數模擬獵物的防禦的演化時，應考慮捕食者根據毒性與取得的營養間的平衡所做的決定。

棲地分割是否導致擬態的毒斑蝶亞科種類的分化？

2010-02-14T22:32:00.000+08:00

photo from http://www.ucl.ac.uk/taxome/jim/Mim/moth.html

source: Hill RI. (2010) Habitat segregation among mimetic ithomiine butterflies (Nymphalidae). Evol. Ecol. 24: 273-285. [abstract]

簡介
擬態生物學家對於共棲並擬態蝴蝶的翅紋多樣性，抱持著讚嘆卻無法有合理的解釋，因為在天擇的作用下，捕食者對於擬態的斑紋的選汰，應該會迫使捕食者採用同樣的斑紋以加強擬態的效應。擬態群間的棲地分割是一個已經用來測試的假說，且可能可以用來解釋擬態群的高多樣性，但截至目前為止，以這個假說來討論擬態群的分化的研究仍然很少。本篇基於這個假說，測試不同的擬態群是否限定在特定的棲地中。作者取樣分布自厄瓜多的毒斑蝶亞科中9個不連續的擬態群且分屬於4種不同的棲地。毒斑蝶亞科的種類與數量在開放式棲地都是最少的，棲地的偏好性也在大多數的種類被觀察到。不同的擬態群間的棲地有顯著的不同，顯示不同的棲地是維持擬態群多樣性的重要因素。然而，仍然觀察到擬態群的分佈有重疊的情況，特別是在2個數量最多的擬態群中。這樣的分佈格局是被較為普遍的種類所驅動，而稀有種類與數量較多種類的分布僅有較薄弱的證據顯示其符合。因此，棲地分割在擬態的多樣性的演化中，僅對於數量較多的model有其貢獻，但這個因子對於整體演化的影響度可能比起其他的因子薄弱。

條紋紅椿(Striated shield bug)在不同時期改變自身保護色以躲避天敵

2010-02-14T12:58:00.000+08:00

Gamberle-Stille G, Johansen AI, Tullberg BS. (2010) Change in protective coloration in the striated shieldbug Graphosoma lineatum (Heteroptera: Pentatomidae): predator avoidance and genealization among different life stages. Evol. Ecol. 24: 423-432. [abstract]

簡介

動物用以保護自身的顏色主要有兩種形式：隱蔽與警戒，而有些物種在不同的成長時期採取改變體色的策略用以躲避天敵。本篇以Striated shieldbug為例，在夏天晚期時該椿象的體色為較隱蔽的灰白褐色，而到了隔天春天早期時，該椿象的體色變為紅與黑的條紋。本篇主要測試這種椿象在比較其在不同的發育時期，其隱蔽的體色是否會影響警戒色的效用。在測試中隱蔽型與警戒型的椿象展示給無經驗的家雞，以測試其經驗初期對於不同體色的忌避反應、學習與普遍化反應。測試使用三種形式的椿象：幼期體色、成蟲期的隱蔽體色與警戒體色。其結果顯示家雞最快發現警戒體色的不適口，其次依序為隱蔽體色與幼期體色。家雞在測試中並為學得避免取食幼期體色的個體，但成蟲期的兩種體色皆被學習並且避免捕食。此結果顯示隱蔽型的體色可能也代表較為減弱的警戒色，並且可避免被沒經驗的鳥類捕食。

失去螯肢的雄性招潮蟹如何躲避其他個體的侵略？

2010-01-29T17:43:00.000+08:00

photo from http://www.flickr.com/photos/wildsingapore/427821933/

source: Booksmythe I, Milner RNC, Jennions MD & Backwell PRY. (2010) How do weaponless male fiddler crabs acoid aggression? Behavioral Ecology and Sociobiology 64(3): 485-491. [abstract]

許多物種為了避免雄性間的競爭，會藉由擬態雌性的特徵來避免自身受到傷害。在招潮蟹中，雄性特化的大螯通常是用以競爭及防禦領域，但某些個體會因為打鬥時受傷以致失去了大螯，而這是否會影響其生存與防禦其他個體侵略的能力？本篇作者根據這個想法，測試了三個假設:(1)雄性招潮蟹是否將失去大螯招潮蟹誤認為雌性個體？(2)失去大螯的招潮蟹在取得、防禦與維持領域上是否較弱？(3)失去大螯的招潮蟹是否比其他健全的雄性個體更謹慎？其結果顯示雖然失去大螯的雄蟹與健全的雄蟹取得領域的方式不同，但其成功率並無顯著差異；雖然健全的雄蟹會將失去大螯的雄蟹當成雌蟹，但並沒有證據顯示失去大螯的雄蟹是有目的的擬態雌蟹。失去大螯的雄蟹也顯出其為了避免衝突，而有不同保衛領域的策略。

[Book] Dazzled and Deceived: Mimicry and Camouflage

2010-01-27T13:45:00.000+08:00

本書中介紹動物用於保護的顏色，諸如隱蔽色、警戒色與擬態等，並且連結其自然現象與演化機制，從基因層次至天擇都在本書的討論範圍中；除此之外，作者也實地訪談實際研究動物體色演化的科學家，記錄實際的經驗與難題，補足自達爾文以來，關於動物體色演化觀念的變化與挑戰。作者也進一步的討論動物的保護體色應用於人類世界的實例，如陸戰隊的野戰服裝的顏色如何與背景達成一致，以達成隱蔽的效果，都是參考自然界的應用實例。
[相關書介]
Nature
Barnes & Noble
Nature History
Yale
BBC

在貝氏擬態中，高豐度的model可能允許mimic性狀在演化過程中漸變

2009-12-16T23:07:00.000+08:00

文獻來源：Kikuchi DW & Pfennig DW. 2009. High-model abundance may permit the gradual evolution of Batesian mimicry: an experimental test. Proc. R. Soc. B. in press. [page]

簡介

貝氏擬態中mimic的演化被認為是追尋著model而變化其擬態斑紋組，然而在演變的過程中，斑紋的變化是突然間的劇烈變化，並且快速的達到性狀固定(phenotype fixed)，或是逐漸變化淘汰不被環境所偏好的性狀，l這個問題在各派學說中並未達到共識。本篇研究以珊瑚蛇擬態群為例，透過捕食實驗與性狀在演化關係樹上的分佈，推測mimic性狀的演化方向。從捕食實驗的結果來看，接近擬態的mimic與不顯眼的斑紋在model豐度高的時候並不容易遭受攻擊，反之在model豐度低的時候則以上兩者皆遭受高度攻擊。性狀演化的結果則顯示，mimic的斑紋演化趨勢是從隱蔽的顏色到半擬態型，再到擬態型。這篇文章提供了mimic斑紋組的演化在model豐度高的條件下，可以經由逐漸的變化漸進參與擬態群。

警戒性與貝氏擬態是否一定需要醒目顏色配合? 研究顯示歐洲蝮蛇的隱匿但具辯識性的斑紋可避免掠食者的攻擊

2009-10-08T10:47:00.000+08:00

文獻來源: WüSTER W, ALLUM CSE, BIRTA BJARGARDOTTIR I, BAILEY KL, DAWSON KJ, GUENIOUI J, LEWIS J, MCGURK J, MOORE AG, NISKANEN M, POLLARD CP. 2004. Do aposematism and Batesian mimicry require bright colours? A test, using European viper markings. Proceedings of the Royal Society of London. Biological sciences 271(1556): 2495-2499. [全文下載]

Abstract
Predator avoidance of noxious prey, aposematism and defensive mimicry are normally associated with bright, contrasting patterns and colours. However, noxious prey may be unable to evolve conspicuous coloration because of other selective constraints, such as the need to be inconspicuous to their own prey or to specialist predators. Many venomous snakes, particularly most vipers, display patterns that are apparently cryptic, but nevertheless highly characteristic, and appear to be mimicked by other, non-venomous snakes. However, predator avoidance of viper patterns has never been demonstrated experimentally. Here, the analysis of 813 avian attacks on 12 636 Plasticine snake models in the field shows that models bearing the characteristic zigzag band of the adder (Vipera berus) are attacked significantly less frequently than plain models. This suggests that predator avoidance of inconspicuously but characteristically patterned noxious prey is possible. Our findings emphasize the importance of mimicry in the ecological and morphological diversification of advanced snakes.

圖片連結: wikipedia (photo credit: Marek Szczepanek)

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

2009-09-22T18:06:00.000+08:00

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

2009-09-22T17:52:00.000+08:00

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.

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)

2009-09-21T15:48:00.000+08:00

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

Abstract
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

非洲白鳳蝶的系統發生學與擬態翅紋的演化

2009-09-21T10:12:00.000+08:00

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.

Venomous Sea Snakes Play Heads Or Tails With Their Predators

2009-08-10T16:07:00.000+08:00

Rasmussen.A.R, Elmberg.J. 2009. 'Head for my tail': a new hypothesis to explain how venomous sea snakes avoid becoming prey. Marine Ecology DOI: 10.1111/j.1439-0485.2009.00318

Sea snakes are widespread and conspicuous inhabitants of shallow waters in the Indian and Pacific Oceans. They are agile top predators and possess extremely potent venom, but they are still susceptible to predation by large fish, e.g. sharks, and other vertebrates. We describe how crevice-probing and temporarily non-vigilant Yellow-lipped Sea Kraits Laticauda colubrina twist the tail around their length axis so that the tail tip's lateral aspect corresponds to the dorsal view of the head. In doing so, coloration and pattern in combination with tail movement and posture make the tail appear very similar to the (non-visible and foraging) head. We examined 98 Laticauda spp. sea snakes in three major museum collections and reviewed the literature to assess the generality and implications of our field observations. This leads us to hypothesize that a combination of: (i) head and tail being similarly coloured and patterned, and (ii) the tail being motioned to resemble the head, is a hitherto overlooked mimetic and 'prophylactic' anti-predator adaptation in the L. colubrina complex, and possibly in other species of sea snake. We propose this is a concerted behavioural–morphological adaptation, and we briefly speculate about its possible fitness trade-offs as well as its origin. Explicit and testable predictions derived from the hypothesis are presented.

Higher survival of aposematic prey in close encounters with predators: an experimental study of detection distance

2009-07-27T14:49:00.000+08:00

Animal Behavior, Vol. 78, No. 1, 111-116
Gabriella Gamberale-Stille, Carolina Bragée and Birgitta S. Tullberg

Department of Zoology, Stockholm University, Sweden

Aposematic animals are often conspicuous. It has been hypothesized that one function of conspicuousness in such prey is to be detected from afar by potential predators: the ‘detection distance hypothesis’. The hypothesis states that predators are less prone to attack at long detection range because more time is allowed for making the ‘correct’ decision not to attack the unprofitable prey. The detection distance hypothesis has gained some experimental support in that time-limited predators make more mistakes. To investigate effects of prey presentation distance we performed two experiments. First, in experiment 1, we investigated at what distance chicks, Gallus gallus domesticus, could see the difference in colour between aposematic and plain mealworms. Birds chose the correct track in a two-way choice when prey were at 20, 40 and 60 cm distance but not at 80 cm. Second, in experiment 2, fifth-instar larvae of the aposematic bug Lygaeus equestris were presented to experienced chicks at 2, 20 or 60 cm distance. We found no difference in attack probability between distances. However, prey mortality was significantly lower for the shortest presentation distance. In conclusion, we found no support for the hypothesis that aposematic prey benefit from long-range detection; in fact they benefit from short-distance detection. This result, and others, suggests that the conspicuousness of aposematic prey at a distance may simply be a by-product of an efficient signalling function after detection.

Keywords: attack mortality; attention; detection distance; domestic chick; foraging behaviour; Gallus gallus domesticus; Lygaeus equestris; warning coloration

Higher survival of aposematic prey in close encounters with predators: an experimental study of detection distanc

2009-06-26T11:32:00.000+08:00

Higher survival of aposematic prey in close encounters with predators: an experimental study of detection distanc e

Animal Behaviour, Vol. 78, No. 1, 111-116
Gabriella Gamberale-Stille, Carolina Bragée and Birgitta S. Tullberg

Department of Zoology, Stockholm University, Sweden

Keywords: attack mortality; attention; detection distance; domestic chick; foraging behaviour; Gallus gallus domesticus; Lygaeus equestris; warning coloration

Mimicry in coral reef fish: how accurate is this deception in terms of color and luminance?

2009-05-08T11:56:00.000+08:00

Mimicry in coral reef fish: how accurate is this deception in terms of color and luminance?

Behavioral Ecology, Vol. 20, No. 3. 459-468

Karen L. Cheney^a and N. Justin Marshall^b

(a)School of Integrative Biology (b)School of Biomedical Sciences, The University of Queensland

Batesian and aggressive mimics are considered to be under selectivepressure to resemble their models, whereas signal receiversare under selection to discriminate between mimics and models.However, the perceptual ability of signal receivers to discriminatebetween mimics and models is rarely studied. Here we examined15 model–mimic coral reef fish pairs using nonsubjectivemethods to judge the accuracy of mimics in terms of color andluminance. We then investigated the potential ability of fishwith various visual systems to discriminate between model andmimic colors using theoretical vision models. We found the majorityof mimics closely resembled models in terms of color and luminancefrom a nonsubjective perspective. However, fish that have potentiallytrichromatic (3 distinct cone photoreceptors) visual systemswith ultraviolet sensitivity had a much better capacity to discriminatebetween models and mimics compared with fish with midrange sensitivityor dichromatic (2 cone photoreceptors) fish. The spectral reflectanceof color patches reflected by models and mimics became moresimilar with an increase in depth, indicating that signal receiversmay be more likely to distinguish mimics from models in habitatslocated closer to the surface. There was no such change in luminancecontrast with depth. The selection pressure on mimics to accuratelyresemble their model is therefore predicted to vary dependingon the visual system of the signal receiver and the light environment.

Keywords: aggressive mimicry, animal signaling, Batesian, color vision, signal accuracy.

A single origin of Batesian mimicry among hybridizing populations of admiral butterflies (Limenitis arthemis) rejects an evolutionary reversion to the

2009-04-16T16:45:00.000+08:00

A single origin of Batesian mimicry among hybridizing populations of admiral butterflies (Limenitis arthemis) rejects an evolutionary reversion to the ancestral phenotype

Wesley K. Savage and Sean P. Mullen
Department of Biological Sciences, Lehigh University

Batesian mimicry is a fundamental example of adaptive phenotypic evolution driven by strong natural selection. Given the potentially dramatic impacts of selection on individual fitness, it is important to understand the conditions under which mimicry is maintained versus lost. Although much empirical and theoretical work has been devoted to the maintenance of Batesian mimicry, there are no conclusive examples of its loss in natural populations. Recently, it has been proposed that non-mimetic populations of the polytypic Limenitis arthemis species complex represent an evolutionary loss of Batesian mimicry, and a reversion to the ancestral phenotype. Here, we evaluate this conclusion using segregating amplified fragment length polymorphism markers to investigate the history and fate of mimicry among forms of the L. arthemis complex and closely related Nearctic Limenitis species. In contrast to the previous finding, our results support a single origin of mimicry within the L. arthemis complex and the retention of the ancestral white-banded form in non-mimetic populations. Our finding is based on a genome-wide sampling approach to phylogeny reconstruction that highlights the challenges associated with inferring the evolutionary relationships among recently diverged species or populations (i.e. incomplete lineage sorting, introgressive hybridization and/or selection).

Keywords: wing pattern evolution, mimicry, amplified fragment length polymorphism, Limenitis phylogeny, gene flow

Concealed by conspicuousness: distractive prey markings and backgrounds

2009-04-07T15:44:00.000+08:00

Concealed by conspicuousness: distractive prey markings and backgrounds

Proceedings of Royal Society B (2009) vol. 276, no. 1663, 1905-1910
Marina Dimitrova(1), Nina Stobbe(2), H. Martin Schaefer(2) and Sami Merilaita(1)

(1)Department of Zoology, Stockholm University
(2)Department of Evolutionary Biology and Animal Ecology, Faculty of Biology, University of Freiburg Hauptstrasse 1

High-contrast markings, called distractive or dazzle markings, have been suggested to draw and hold the attention of a viewer, thus hindering detection or recognition of revealing prey characteristics, such as the body outline. We tested this hypothesis in a predation experiment with blue tits (Cyanistes caeruleus) and artificial prey. We also tested whether this idea can be extrapolated to the background appearance and whether high-contrast markings in the background would improve prey concealment. We compared search times for a high-contrast range prey (HC-P) and a low-contrast range prey (LC-P) in a high-contrast range background (HC-B) and a low-contrast range background (LC-B). The HC-P was more difficult to detect in both backgrounds, although it did not match the LC-B. Also, both prey types were more difficult to find in the HC-B than in the LC-B, in spite of the mismatch of the LC-P. In addition, the HC-P was more difficult to detect, in both backgrounds, when compared with a generalist prey, not mismatching either background. Thus, we conclude that distractive prey pattern markings and selection of microhabitats with distractive features may provide an effective way to improve camouflage. Importantly, high-contrast markings, both as part of the prey coloration and in the background, can indeed increase prey concealment.

keywords: crypsis, predation, dazzle, disruptive coloration, camouflage, background matching

Mimicry, colour forms and spectral sensitivity of the bluestriped fangblenny, Plagiotremus rhinorhynchos

2009-04-06T13:00:00.000+08:00

Mimicry, colour forms and spectral sensitivity of the bluestriped fangblenny, Plagiotremus rhinorhynchos

Proceedings of the royal society series B, vol. 276, no. 1662, 1565-1673
photo from Nature 433, 211-212

Karen L Cheney(1), Charlotta Skogh(2), Nathan S Hart(2) and N. Justin Marshall(2)

(1)School of Integrative Biology, The University of Queensland St Lucia
(2)School of Biomedical Sciences, The University of Queensland St Lucia

Animals change their body coloration for a variety of purposes including communication, thermoregulation and crypsis. The cues that trigger adaptive colour change are often unclear, and the role of colour vision remains largely untested. Here, we investigated the bluestriped fangblenny (Plagiotremus rhinorhynchos), an aggressive mimic that changes its body coloration to impersonate a variety of coral reef fishes. In this field, we determined the fish species that the fangblenny associated with and measured the spectral reflectance of mimics and their models. We measured the spectral absorbance characteristics of the retinal photoreceptor visual pigments in the bluestriped fangblenny using microspectrophotometry and found it to have rod photoreceptors (λmax 498 nm), single cones (449 nm) and double cones (561 nm principal member; 520 nm accessory member). Using theoretical vision models, fangblennies could discriminate between the colours they adopted and the colours of the fish they associated with. Potential signal receivers (Abudefduf abdominalis and Ctenochaetus strigosus) perceived colours of most mimics to closely resemble fishes they associated with. However, fishes with ultraviolet-sensitive visual pigments were better at discriminating between mimics and models. Therefore, colour vision could be used by fangblennies when initiating colour change enabling them to accurately resemble fishes they associate with and to avoid detection by signal receivers.

Keywords: facultative mimicry, microspectrophotometry, colour vision, colour change, spectral reflectance, coral reef fish

Population dynamics of Müllerian mimicry under interspecific competition

2009-03-26T11:36:00.000+08:00

Population dynamics of Müllerian mimicry under interspecific competition

Ecological Modelling, Vol. 220, No. 3, 424-429

Fuga Kumazawa(a), Takahiro Asami(b), Nariyuki Nakagiri(c), Kei-ichi Tainaka(a), Tatsuya Togashi(d), Tatsuo Miyazaki(d) & Jin Yoshimura(a, d, e)

(a) Department of Systems Engineering, Faculty of Engineering, Shizuoka University,
(b) Department of Biology, Shinshu University
(c) School of Human Science and Environment, University of Hyogo
(d) Marine Biosystems Research Center, Chiba University
(e) Department of Environmental and Forest Biology, State University of New York College of Environmental Science and Forestry

We ask what the effects of mutualism on population dynamics of two competitive species are. We model the population dynamics of mutualistic interactions with positive density- and frequency-dependences. We specifically assume the dynamics of Müllerian mimicry in butterflies, where the mortality of both species is reduced depending on the relative frequency of the other species. We assume that the two species are under Lotka–Volterra density-dependent competition. The equilibria are compared with the cases of competition alone. Unlike the traditional model of positive density-dependence, population explosion does not appear in the current dynamics, but the new equilibrium is simply achieved. It is because the effects of positive density- or frequency-dependence are restricted to parts of mortality. Both positive density- and frequency-dependences do promote coexistence of the mimetic species. However, the two models show a distinctive difference for coexistence. The effects of positive density-dependence are rather limited. In contrast, positive frequency-dependence always promotes coexistence, irrespective of environmental conditions. The results may imply that the evolutionary origin of Müllerian mimicry may depend on frequency-dependence (and density-dependence), but that its current population dynamics may depend solely on density-dependence. The role of frequency- and density-dependences on evolutionary dynamics is an open question.

Keywords: Müllerian mimicry; Density-dependence; Frequency-dependence; Mutualism

Butterfly effects in mimicry? Combining signal and taste can twist the relationship of Müllerian co-mimics

2009-02-23T17:18:00.000+08:00

Butterfly effects in mimicry? Combining signal and taste can twist the relationship of Müllerian co-mimics

Behavioural Evology and Sociobiology, Vol. 62, No. 8, 1267-1276

Eira Ihalainen, Leena Lindström, Johanna Mappes and Sari Puolakkainen
Department of Biological and Environmental Science, FI-40014 University of Jyväskylä

Müllerian co-mimics are aposematic species that resemble each other; sharing a warning signal is thought to be mutually beneficial for the co-mimics by reducing per capita predation risk. In Batesian mimicry, edible mimics avoid predation by resembling an aposematic model species. The protection of both the model and the mimic is weakened when the mimics are abundant compared to the models. The quasi-Batesian view suggests that defended (Müllerian) co-mimics, when unequal in their defences, could also show a Batesian-like trend of increasing mortality with increasing abundance of a less defended “mimic”. We manipulated frequencies of unequally distasteful artificial co-mimics that were prey for great tits. The co-mimics had different signals (imperfect mimicry) but were equally preferred by the birds when palatable. Unexpectedly, when unpalatable, one of the signals was easier for the birds to learn to avoid. Consequently, during predator learning, the signal design of the prey strongly affected mortality of the co-mimics; there was an interaction between the signal and frequency treatments, but increasing the frequency of a less defended “mimic” did not increase co-mimic mortalities as predicted. In contrast, in a memory test that followed, the effect of signal design disappeared; if the birds had experienced high frequency of “mimics” during learning, co-mimic mortalities did subsequently increase. Since the effect of co-mimic frequencies on mortalities changed depending on the signal design of the prey and predator experience, the results suggest that mimetic relationship may be an unpredictable interplay of several factors in addition to taste and abundance.

Keywords: Aposematism - Quasi-Batesian mimicry - Predator psychology - Avoidance learning - Memory

The effect of rainforest fragmentation on species diversity and mimicry ring composition of ithomiine butterflies

2009-02-21T11:42:00.000+08:00

The effect of rainforest fragmentation on species diversity and mimicry ring composition of ithomiine butterflies

Insect Conservation and Diversity. 2009. Vol. 2, No. 1, 23-28.
MARCIO UEHARA-PRADO (1,2) and ANDRÉ V.L. FREITAS (1)
1 Departamento de Zoologia, Instituto de Biologia, Universidade Estadual de Campinas
2 Programa de Pós-Graduação em Ecologia, Instituto de Biologia, Universidade Estadual de Campinas

1. Subfamily Ithomiinae comprises about 370 species of Neotropical butterflies associated with humid forest habitats from Mexico to northern Argentina. Adult Ithomiinae are central models in many mimicry rings throughout their range, and are assumed to have high potential as bio-indicators. Here, we compare diversity and composition of Ithomiinae mimicry rings in continuous vs. fragmented landscapes, and evaluate values these butterflies hold for ecological assessment and monitoring of anthropogenic disturbance.

2. Sampling was carried out at four sites inside a large forest block, the Morro Grande State Reserve, and in five forest fragments in a neighbour-fragmented landscape. Butterflies were sampled with portable traps, baited with a fermented mixture of banana and sugar cane juice. Sampling was carried out during the period most favourable for the capture of ithomiine butterflies in southeastern Brazil.

3. There was no difference between landscapes in species richness and diversity index, but dominance index, and the distributions of tribes and mimicry rings between them was clearly different. The higher average light intensity in the understorey of fragments could explain in part the higher abundance of mimicry patterns typical of open sunny habitats, and concomitantly reduced abundance of clearwing mimicry patterns, typical of shaded habitats. These results confirm the potential of ithomiine assemblages as biological indicators of habitat quality.

Keywords: Atlantic rainforest • biological indicators • conservation • Ithomiinae

Octopus mimicking its follower reef fish

2009-02-21T11:35:00.000+08:00

Octopus mimicking its follower reef fish

Journal of Natural History. 2009. Vol. 43. No. 3 & 4. 185-190.
J. P. Krajewski (ab), R. M. Bonaldo (ac), C. Sazima(d), I. Sazima(e)
(a) School of Marine and Tropical Biology, James Cook University
(b) Departamento de Zoologia e Ps-Graduao em Ecologia, Universidade Estadual de Campinas
(c) Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University
(d) Departamento de Parasitologia, Universidade Estadual de Campinas, Campinas
(e) Museu de Zoologia, Universidade Estadual de Campinas, Campinas

We describe a possible example of social mimicry between Octopus insularis and the small grouper Cephalopholis fulva, which frequently associate during foraging at Fernando de Noronha Archipelago, Brazil. The octopus, when swimming backwards, jet-propelled, becomes similar in colour and shape to accompanying C. fulva individuals and is therefore less conspicuous within the fish group. We regard this as an instance of social mimicry, a form of protection against visually-oriented predators in which different species similar in shape and colour mingle for the advantage of grouping. Even when swimming backwards alone, O. insularis may become similar to foraging C. fulva individuals, another putatively protective behaviour. We suggest that the feeding association commonly found between O. insularis and C. fulva minimized the evolutionary costs for the origin of mimicking by the octopus.

Keywords: social mimicry; Octopus insularis; Cephalopholis fulva; foraging association; Fernando de Noronha Archipelago

Mimicry in coral reef fish: how accurate is this deception in terms of color and luminance?

2009-02-20T14:34:00.000+08:00

Mimicry in coral reef fish: how accurate is this deception in terms of color and luminance?

Behavioral Ecology (2009)
Karen L. Cheney(a) and N. Justin Marshall(b)
(a) School of Integrative Biology (b) School of Biomedical Sciences, The University of Queensland,

Batesian and aggressive mimics are considered to be under selective pressure to resemble their models, whereas signal receivers are under selection to discriminate between mimics and models. However, the perceptual ability of signal receivers to discriminate between mimics and models is rarely studied. Here we examined 15 model–mimic coral reef fish pairs using nonsubjective methods to judge the accuracy of mimics in terms of color and luminance. We then investigated the potential ability of fish with various visual systems to discriminate between model and mimic colors using theoretical vision models. We found the majority of mimics closely resembled models in terms of color and luminance from a nonsubjective perspective. However, fish that have potentially trichromatic (3 distinct cone photoreceptors) visual systems with ultraviolet sensitivity had a much better capacity to discriminate between models and mimics compared with fish with midrange sensitivity or dichromatic (2 cone photoreceptors) fish. The spectral reflectance of color patches reflected by models and mimics became more similar with an increase in depth, indicating that signal receivers may be more likely to distinguish mimics from models in habitats located closer to the surface. There was no such change in luminance contrast with depth. The selection pressure on mimics to accurately resemble their model is therefore predicted to vary depending on the visual system of the signal receiver and the light environment.

Key words: aggressive mimicry, animal signaling, Batesian, color vision, signal accuracy.

Identity of Euploea orontobates Fruhstorfer, 1910 (Lepidoptera: Nymphalidae), a milkweed butterfly from Thailand and Vietnam

2009-02-01T11:13:00.000+08:00

Identity of Euploea orontobates Fruhstorfer, 1910 (Lepidoptera: Nymphalidae), a milkweed butterfly from Thailand and Vietnam

Zootaxa (2009) Vol. 1991, 43-50
A.L. MONASTYRSKII(1) & R.I. VANE-WRIGHT(2) 1Vietnam-Russia Research Tropical Centre 2Department of Entomology, the Natural History Museum, Cromwell Road, London SW7 5BD, UK; & Durrell Institute of Conservation and Ecology, University of Kent

Euploea orontobates Fruhstorfer, 1910, described from south-eastern Thailand (Si Racha district), is demonstrated to be a senior synonym of Euploea conbuom Saito & Inayoshi, 2006, from southern Central Vietnam. The relationships and biogeography of this rare butterfly are discussed, and presented together with comments on the principal mimicry complex among the Euploea species of Indochina.

Keywords: Danainae, Euploea orontobates, Euploea conbuom, synonymy, relationships, Thailand, Vietnam, Sundaland, endemism, biogeography

The role of predator selection on polymorphic aposematic poison frogs

2009-01-31T20:13:00.000+08:00

The role of predator selection on polymorphic aposematic poison frogs

Biology letters (2009) Vol. 5, No. 1, 51-54
Brice P. Noonan, Aaron A. Comeault
Department of Biology, University of Mississippi, University

Demonstrations of interactions between diverse selective forces on bright coloration in defended species are rare. Recent work has suggested that not only do the bright colours of Neotropical poison frogs serve to deter predators, but they also play a role in sexual selection, with females preferring males similar to themselves. These studies report an interaction between the selective forces of mate choice and predation. However, evidence demonstrating phenotypic discrimination by potential predators on these polymorphic species is lacking. The possibility remains that visual (avian) predators possess an inherent avoidance of brightly coloured diurnal anurans and purifying selection against novel phenotypes within populations is due solely to non-random mating. Here, we examine the influence of predation on phenotypic variation in a polymorphic species of poison frog, Dendrobates tinctorius. Using clay models, we demonstrate a purifying role for predator selection, as brightly coloured novel forms are more likely to suffer an attack than both local aposematic and cryptic forms. Additionally, local aposematic forms are attacked, though infrequently, indicating ongoing testing/learning and a lack of innate avoidance. These results demonstrate predator-driven phenotypic purification within populations and suggest colour patterns of poison frogs may truly represent a ‘magic trait’.

Keywords: aposematic, selection, Dendrobates, magic trait

Warning displays may function as honest signals of toxicity

2009-01-31T17:38:00.000+08:00

Warning displays may function as honest signals of toxicity

Proceedings of Royal Society B (2009) Vol. 276, No. 1658, 871-877
Jonathan D. Blount(1), Michael P. Speed(2), Graeme D. Ruxton(3), Philip A. Stephens(4)
1 Centre for Ecology and Conservation, School of Biosciences, University of Exeter, Cornwall Campus
2 School of Biological Sciences, Bioscience Building, University of Liverpool
3Division of Environmental and Evolutionary Biology, Institute of Biomedical and Life Sciences, University of Glasgow
4 School of Biological and Biomedical Sciences, University of Durham

Many prey species use colourful ‘aposematic’ signalling to advertise the fact that they are toxic. Some recent studies have shown that the brightness of aposematic displays correlates positively with the strength of toxicity, suggesting that aposematic displays are a form of handicap signal, the conspicuousness of which reliably indicates the level of toxicity. The theoretical consensus in the literature is, however, at odds with this finding. It is commonly assumed that the most toxic prey should have less bright advertisements because they have better chances of surviving attacks and can therefore reduce the costs incurred by signalling. Using a novel theoretical model, we show that aposematic signals can indeed function as handicaps. To generate this prediction, we make a key assumption that the expression of bright displays and the storage of anti-predator toxins compete for resources within prey individuals. One shared currency is energy. However, competition for antioxidant molecules, which serve dual roles as pigments and in protecting prey against oxidative stress when they accumulate toxins, provides a specific candidate resource that could explain signal honesty. Thus, contrary to the prevailing theoretical orthodoxy, warning displays may in fact be honest signals of the level of (rather than simply the existence of) toxicity.

Keywords: aposematism, handicap signal, toxicity, trade-off

Role of different colours of aposematic insects in learning, memory and generalization of naïve bird predators

2009-01-31T16:45:00.000+08:00

Role of different colours of aposematic insects in learning, memory and generalization of naïve bird predators

Animal Behaviour (2009) Vol. 77, No. 2, 327-336
Kateřina Svádová(a, b), Alice Exnerová(a), Pavel Štys(a), Eva Landová(a), Jan Valenta(c), Anna Fučíková(c) and Radomír Socha(d)
aDepartment of Zoology, Charles University, Praha, Czech Republic
bDepartment of Biology, University Hradec Králové, Czech Republic
cDepartment of Chemical Physics and Optics, Charles University, Praha, Czech Republic
dBiology Center ASCR, Institute of Entomology, České Budějovice, Czech Republic

Among the various properties of visual warning signals, colour seems to be especially important for avian predators. We tested the role of particular colours of an aposematic insect (firebug, Pyrrhocoris apterus; Heteroptera: Pyrrhocoridae) in unlearned avoidance, learning, memory and generalization of a naïve avian predator (great tit, Parus major). The wild type of the firebug is aposematic, red-and-black, and its colour mutants (white, yellow, orange) retain the same black pattern; the bug can be made artificially nonaposematic (painted uniformly brown). Wild-caught great tits avoid the firebug depending on colour, and their reaction to variously coloured prey is a result of avoidance learning and may vary according to their experience. We trained naïve great tits to avoid firebugs of different colours, and then gave some birds a memory test with firebugs of the same colour and other birds a generalization test with firebugs of a different colour. Naïve, hand-reared great tits showed no initial avoidance and attacked firebugs irrespective of colour. They learned to avoid all the colour forms at a similar rate. The generalization was asymmetric: birds that learned to avoid red firebugs did not generalize their experience to yellow or white mutants whereas birds that learned to avoid yellow mutants generalized their experience to red firebugs. The red colour thus represents a more effective signal than the yellow; predation by birds could have played a crucial role in selectively favoured evolutionary transitions from yellow to red coloration in pyrrhocorids.

Keywords: asymmetric generalization; avoidance learning; firebug; great tit; Parus major; peak shift; Pyrrhocoris apterus; signal memorability; warning signal

The protective value of conspicuous signals is not impaired by shape, size, or position asymmetry

2008-12-30T10:54:00.000+08:00

The protective value of conspicuous signals is not impaired by shape, size, or position asymmetry

Behavioral Ecology (2009) Vol. 20, No. 1, 96-102
Martin Stevens, Sarah A. Castor-Perry, and Jessica R.F. Price
Department of Zoology, University of Cambridge

Various conspicuous signals in nature promote initial and learned avoidance by predators. It is widely thought that such signals are most effective when highly symmetrical in features such as size and shape, supported by recent laboratory experiments with domestic chicks and artificial prey. However, no study has investigated the effect of asymmetry on conspicuous signals in a natural setting, where viewing distances, angles, predator species, and light conditions vary and where predators encounter prey sequentially rather than simultaneously. We undertook 2 field experiments with artificial gray-scale prey, marked with a pair of white markings presented to wild avian predators, to test the effect of asymmetry on the survival value of conspicuous signals in the field. Experiment 1 had treatments with symmetrical spots or with spots asymmetrical in area between 5 and 50%. All marked
treatments survived better than unmarked controls, but there was no benefit of being symmetrical. Experiment 2 tested the effect of possessing markings asymmetrical for shape or position and any additive effect of these 2 features. Again, symmetry conferred no benefit and targets with markings asymmetrical for position and/or shape survived equally well as those with symmetrical arrangements. These findings indicate that asymmetry in warning signals may not be costly to prey in nature or be of less importance compared with other features of the signal, such as color and overall size.

Keywords: antipredator coloration, aposematism, birds, eyespots, predation, symmetry.

Testing the predatory behaviour of Podarcis sicula (Reptilia: Lacertidae) towards aposematic and non-aposematic preys

2008-11-02T13:07:00.001+08:00

Bonacci, Teresa, Gaetano Aloise, Pietro Brandmayr, Tullia Z. Brandmayr and Massimo Capula. 2008. Testing the predatory behaviour of Podarcis sicula (Reptilia: Lacertidae) towards aposematic and non-aposematic preys. Amphibia- Reptilia. 29 (3): 449-453. [t.bonacci@unical.it]

Abstract: Food preferences and the effects of prey chemical repellents in the dietary behaviour of Podarcis sicula were tested using four species of Carabid beetles as prey models. The goal of the study was to assess (i) the ability of P. sicula to recognize insect preys provided with chemical repellents and aposematic colorations under laboratory conditions, and (ii) the importance of chemical signals used by the prey model as antipredatory strategy. Preys used in this study were Brachinus sclopeta and Anchomenus dorsalis (aposematic species) and Amara anthobia and A. aenea (non-aposematic species). Aposematic species are characterized by warning color pattern and by production of chemical repellents, while non-aposematic ones do not. Amara anthobia and A. aenea were attacked with high frequency by P. sicula, Brachinus sclopeta and Anchomenus dorsalis with low frequency. Non-aposematic species were preyed more often than the aposematic ones. Brachinus sclopeta was preyed after low latency, while Amara anthobia and A. aenea after long latency. Non-aposematic species were captured and eaten without difficulty, while when B. sclopeta or A. dorsalis were captured, lizards always tossed their head and then rub the snout on the soil, probably because of the unpalatability of aposematic preys.

Optimal-Foraging Predator Favors Commensalistic Batesian Mimicry

2008-10-20T15:42:00.000+08:00

Optimal-Foraging Predator Favors Commensalistic Batesian Mimicry

Atsushi Honma1¤*, Koh-ichi Takakura2, Takayoshi Nishida1

1 Laboratory of Insect Ecology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan, 2 Osaka City Institute of Public Health and Environmental Science, Osaka, Japan

Background

Mimicry, in which one prey species (the Mimic) imitates the aposematic signals of another prey (the Model) to deceive their predators, has attracted the general interest of evolutionary biologists. Predator psychology, especially how the predator learns and forgets, has recently been recognized as an important factor in a predator–prey system. This idea is supported by both theoretical and experimental evidence, but is also the source of a good deal of controversy because of its novel prediction that in a Model/Mimic relationship even a moderately unpalatable Mimic increases the risk of the Model (quasi-Batesian mimicry).

Methodology/Principal Findings

We developed a psychology-based Monte Carlo model simulation of mimicry that incorporates a “Pavlovian” predator that practices an optimal foraging strategy, and examined how various ecological and psychological factors affect the relationships between a Model prey species and its Mimic. The behavior of the predator in our model is consistent with that reported by experimental studies, but our simulation's predictions differed markedly from those of previous models of mimicry because a more abundant Mimic did not increase the predation risk of the Model when alternative prey were abundant. Moreover, a quasi-Batesian relationship emerges only when no or very few alternative prey items were available. Therefore, the availability of alternative prey rather than the precise method of predator learning critically determines the relationship between Model and Mimic. Moreover, the predation risk to the Model and Mimic is determined by the absolute density of the Model rather than by its density relative to that of the Mimic.

Conclusions/Significance

Although these predictions are counterintuitive, they can explain various kinds of data that have been offered in support of competitive theories. Our model results suggest that to understand mimicry in nature it is important to consider the likely presence of alternative prey and the possibility that predation pressure is not constant.

[Article]Being conspicuous and defended: selective benefits for the individual

2008-10-18T20:20:00.000+08:00

Being conspicuous and defended: selective benefits for the individual

Christina G. Halpin, John Skelhorn and Candy Rowe

Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Henry Wellcome Building, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK

Aposematic insects conspicuously advertise their unprofitability to potential predators. However, when these prey initially evolved, they were likely to have been rare and presumably at a greater risk of being detected and killed by naive predators. Both kin and individual selection theories have been used in attempts to explain this apparent paradox, with much of the empirical research supporting kin selection–based theories. Here, we experimentally test how chemical defence levels in prey and avian color biases influence the probability of a rare conspicuous morph having an initial survival advantage. We used newly hatched domestic chicks (Gallus gallus domesticus) foraging on green and purple prey, on a green or purple background, to model the evolutionary scenario of a rare conspicuous morph arising in a population of already defended cryptic prey. Defended prey were produced by spraying them with quinine solution, which the birds readily detect and can learn to avoid. Although attack rates were initially similar for both defended prey types, the chicks only learned to avoid defended prey when they were conspicuous, not when they were cryptic. In addition, defended conspicuous prey were more likely to be rejected on attack than defended cryptic prey, even when first encountered by a predator. These data suggest that there could be a selective advantage for a rare conspicuous morph to arise in a population of cryptic defended prey due to increased avoidance learning and taste-rejection in naive predators. Our findings also suggest that being a non-preferred color and/or highly defended will increase the probability of this evolutionary scenario.

keywords: aposematism, avoidance learning, color bias, predation, receiver psychology, taste-rejection, warning signal.

[Article]Dazzle coloration and prey movement

2008-10-18T20:03:00.000+08:00

Dazzle coloration and prey movement

Martin Stevens1, Daniella H. Yule1, Graeme D. Ruxton2

1Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
2Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK

Many traits in animals reduce the rate of attack from visually hunting predators, including camouflage, warning signals and mimicry. In addition, some animal markings may reduce the likelihood that an attack ends in successful capture. These might include dazzle markings, high-contrast patterns that make the estimation of speed and trajectory difficult. However, until now, no study has experimentally tested whether some markings may achieve such an effect. We developed a computer ‘game’ where human ‘predators’ have to capture computer-generated prey moving across a background. In two experiments, we find that although uniform camouflaged targets were among the hardest to capture, so were a range of high-contrast conspicuous patterns, such as bands and zigzags. Prey were also more difficult to capture against more heterogeneous than uniform backgrounds, and at faster speeds of movement. As such, we find the first experimental evidence that conspicuous patterns, similar to those found in a wide range of real animals, make the capture of moving prey more challenging. Various anti-predator markings may work prey during motion, and some animals may combine such dazzle patterns with other functions, such as camouflage, thermoregulation, sexual and warning signals.

keywords: protective coloration, motion, conspicuousness, vision, predation, dazzle

[Artical]Can't tell the caterpillars from the trees: countershading enhances survival in a woodland

2008-10-18T19:53:00.000+08:00

Can't tell the caterpillars from the trees: countershading enhances survival in a woodland

Hannah M. Rowland1, Innes C. Cuthill2, Ian F. Harvey1, Michael P. Speed1, Graeme D. Ruxton3

1 School of Biological Sciences, University of Liverpool, Biosciences Building, Crown Street, Liverpool L69 7ZB, UK
2 School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK
3Division of Environmental and Evolutionary Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Graham Kerr Building, Glasgow G12 8QQ, UK

Perception of the body's outline and three-dimensional shape arises from visual cues such as shading, contour, perspective and texture. When a uniformly coloured prey animal is illuminated from above by sunlight, a shadow may be cast on the body, generating a brightness contrast between the dorsal and ventral surfaces. For animals such as caterpillars, which live among flat leaves, a difference in reflectance over the body surface may degrade the degree of background matching and provide cues to shape from shading. This may make otherwise cryptic prey more conspicuous to visually hunting predators. Cryptically coloured prey are expected to match their substrate in colour, pattern and texture (though disruptive patterning is an exception), but they may also abolish self-shadowing and therefore either reduce shape cues or maintain their degree of background matching through countershading: a gradation of pigment on the body of an animal so that the surface closest to illumination is darker. In this study, we report the results from a series of field experiments where artificial prey resembling lepidopteran larvae were presented on the upper surfaces of beech tree branches so that they could be viewed by free-living birds. We demonstrate that countershading is superior to uniform coloration in terms of reducing attack by free-living predators. This result persisted even when we fixed prey to the underside of branches, simulating the resting position of many tree-living caterpillars. Our experiments provide the first demonstration, in an ecologically valid visual context, that shadowing on bodies (such as lepidopteran larvae) provides cues that visually hunting predators use to detect potential prey species, and that countershading counterbalances shadowing to enhance cryptic protection.

keywords: countershading, crypsis, predation, animal coloration, defensive coloration

[Article]Learning and the mimicry spectrum: from quasi-Bates to super-Müller

2008-10-17T11:17:00.000+08:00

Learning and the mimicry spectrum: from quasi-Bates to super-Müller

Alexandra C.V. Balogh ^,^a^,, Gabriella Gamberale-Stille^a and Olof Leimar^a

^aDepartment of Zoology, Stockholm University, Sweden

Müllerian mimicry is the mutualistic resemblance between two defended species, while Batesian mimicry is the parasitic resemblance between a palatable species (the mimic) and an unpalatable one (the model). These two kinds of mimicry are traditionally seen as extreme ends of a mimicry spectrum. For the range in between, it has been suggested that mimetic relations between unequally defended species could be parasitic, and this phenomenon has been referred to as quasi-Batesian mimicry. Where a mimetic relation is placed along the mimicry spectrum depends on the assumptions made about predator learning. We used a variant of the Rescorla–Wagner learning model for virtual predators to analyse the different possible components of the mimicry spectrum. Our model entails that the rate of associative learning is influenced by variation in the stimuli to be learned. Variable stimuli, that is, unequal defences, can increase the predator learning rate and thus lead to an increased level of mutualism in a mimetic relation. In our analysis, we made use of the concepts of super-Müllerian mimicry, where the benefit of mimicry is even greater than in traditional Müllerian mimicry, and quasi-Müllerian mimicry, where mimicry by a palatable mimic is mutualistic. We suggest that these types of mimicry should be included in the mimicry spectrum along with Müllerian, Batesian and quasi-Batesian mimicry.

Keywords: associative learning; mutualism; Müllerian mimicry; quasi-Batesian mimicry; Rescorla–Wagner model

[Article]Multimodal warning signals for a multiple predator world

2008-09-29T18:38:00.000+08:00

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

Center for Sound Communication, Institute of Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York 14853, USA
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).

Top

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]Mimetic butterflies support Wallace's model of sexual dimorphism

2008-08-05T14:06:00.000+08:00

Mimetic butterflies support Wallace's model of sexual dimorphism
Proc Biol Sci. 2008 Jul 22;275(1643):1617-24.
Krushnamegh Kunte

Section of Integrative Biology, University of Texas at Austin, 1 University Station C 0930, Austin, TX 78712-0253, USA Theoretical and empirical observations generally support Darwin's view that sexual dimorphism evolves due to sexual selection on, and deviation in, exaggerated male traits. Wallace presented a radical alternative, which is largely untested, that sexual dimorphism results from naturally selected deviation in protective female coloration. This leads to the prediction that deviation in female rather than male phenotype causes sexual dimorphism. Here I test Wallace's model of sexual dimorphism by tracing the evolutionary history of Batesian mimicry—an example of naturally selected protective coloration—on a molecular phylogeny of Papilio butterflies. I show that sexual dimorphism in Papilio is significantly correlated with both female-limited Batesian mimicry, where females are mimetic and males are non-mimetic, and with the deviation of female wing colour patterns from the ancestral patterns conserved in males. Thus, Wallace's model largely explains sexual dimorphism in Papilio. This finding, along with indirect support from recent studies on birds and lizards, suggests that Wallace's model may be more widely useful in explaining sexual dimorphism. These results also highlight the contribution of naturally selected female traits in driving phenotypic divergence between species, instead of merely facilitating the divergence in male sexual traits as described by Darwin's model.
Keywords
Batesian mimicry, polymorphism, female-limited mimicry, directional selection, stabilizing sexual selection, convergence

[Article]The role of eyespots as anti-predator mechanisms, principally demonstrated in the Lepidoptera

2008-08-03T21:14:00.000+08:00

Review Article

The role of eyespots as anti-predator mechanisms, principally demonstrated in the Lepidoptera

Martin Stevens ^a1
^a1 Ecology of Vision, School of Biological Sciences, University of Bristol, Woodland Road, Bristol, BS8 1UG. UK (E-mail: Martin.Stevens@bristol.ac.uk)

Abstract

Eyespots are found in a variety of animals, in particular lepidopterans. The role of eyespots as antipredator mechanisms has been discussed since the 19th Century, with two main hypotheses invoked to explain their occurrence. The first is that large, centrally located eyespots intimidate predators by resembling the eyes of the predators' own enemies; the second, though not necessarily conflicting, hypothesis is that small, peripherally located eyespots function as markers to deflect the attacks of predators to non-vital regions of the body. A third possibility is also proposed; that eyespots intimidate predators merely because they are novel or rarely encountered salient features. These hypotheses are reviewed, with special reference given to avian predators, since these are likely to be the principal visually hunting predators of the lepidopterans considered. Also highlighted is the necessity to consider the potential influence of sexual selection on lepidopteran wing patterns, and the genetics and development of eyespot formation.

Key Words: eyespots; receiver psychology; antipredator signals; Lepidoptera; deflection; startle displays; false-head; visual signals; colour patterns.

[Debate]珊瑚蛇與奶蛇擬態經典案例的諸多疑點

2008-06-12T10:57:00.000+08:00

Milk snake與Coral snake所形成的putative mimicry complex成為擬態生物學研究的經典已達一世紀之久. 但是這個擬態群一直存在著兩個違背Batesian mimicry預測的基本問題: (1) 被認為是mimic的奶蛇數量遠比被認為是model的coral snake為多; (2) 兩者不一定(而且經常)是不共棲的. 針對model與mimic不一定共棲的問題, 已經有"allopatric mimicry"這個理論所討論, 對於兩者個相對豐度的問題則應追溯至Brower & Brower (1962)以及Greene & McDiarmid (1981)的文章. Harper & Pfennig (2008)的文章則以族群遺傳學的方法證實了身為mimic的milk snake雄性會進行遷徙, 而且遷徙到coral snake不存在的地區, 間接地提供allopatric mimicry存在的族群遺傳學事證. 然而倒底是什麼記憶力, 學習能力與辯識力好的predator讓allopatric mimicry能夠存在, 則應該是下一個研究的目標.

Brattstrom, B.H. 1955. The Coral Snake 'Mimic' Problem and Protective Coloration. Evolution 9(2): 217-219.
Dunn, E.R. 1949. Relative Abundance of Some Panamanian Snakes. Ecology 30(1): 39-57.
Brower, L. P. & Brower, J. V. Z. 1962. The relative abundance of model and mimic butterflies in natural populations of the Battus philenor mimicry complex. Ecology 43: 154–158.
Clarke, C. & Sheppard, P. M. 1975. The genetics of the mimetic butterfly Hypolimnas bolina (L.). Phil. Trans. R. Soc. B 272: 229–265.
Greene, H. W. & McDiarmid, R. Y. 1981. Coral snake mimicry: does it occur? Science 213: 1207–1212.
Harper, G.R., Pfennig, D.W. 2008. Selection overrides gene flow to break down maladaptive mimicry. Nature 451: 1103-1106.
Pfennig, D. W., Harcombe, W. R. & Pfennig, K. S. 2001. Frequency-dependent Batesian mimicry. Nature 410: 323.
Ruxton, G. D., Sherratt, T. N. & Speed, M. P. 2004. Avoiding Attack: The Evolutionary Ecology of Crypsis, Warning Signals and Mimicry. Oxford Univ. Press, Oxford.
Waldbauer, G. P. & Sternburg, J. G. 1987. Experimental field demonstration that two aposematic butterfly color patterns do not confer protection against birds in Northern Michigan. Am. Midl. Nat. 118: 145–152.
Wallace, A. R. 1870. Contributions to the Theory of Natural Selection, Macmillan, London.

其它以奶蛇/珊瑚蛇所形成的擬態群為研究的文章可見David W. Pfennig研究群的著作目錄.

[Practice]變色龍適合拿來當成predator嗎?

2008-06-07T20:21:00.000+08:00

今天以台灣茶斑蛾(Eterusia taiwana)當成prey, 丟給高冠變色龍, 日守宮和攀蜥試試, 原本的想像是--高冠會因為吃到可怕的東西而生氣變色, 這樣我們就知道高冠是否覺得那個東西unpalatable, 這樣不是很棒嗎? 結果丟了斑蛾給四隻高冠, 四隻看了兩眼, 連試也不試, 就走了, 是因為不餓嗎? NO! 丟蟋蟀下去馬上就被吃掉了, 因此那四隻高冠並不是因為不餓才不吃的啊. 接下來再試一次, 仍然只觀察, 但完全不予理會. 所以使用高冠變色龍做為predation test中的naive predator的夢想破碎.

接下來使用的是日守宮. 日守宮看見斑蛾後會馬上下來咬, 但咬完就放開. 看起來是好的開始. 接下來使用攀蜥也有一樣的效果. 但是馬上再拿給同一隻日守宮再試一次, 牠又咬了一次, 然後又放開沒吃. 這代表什麼呢? 表示這個stimulus的強度不足? 不足以讓日守宮產生警戒? 還是第一次的取食失敗並沒有伴隨明顯的視覺警訊 (那隻斑蛾是羽化失敗的大多數翅紋沒有顯示)? 或者是日守宮的記憶力不好? 之後我們又試了瑤山鱷蜥, 一樣是咬了後馬上吐出來. 因此日行性的斑蛾對日行性的蜥蜴是unpalatable是確認的. 然而這些蜥蜴是否能夠成為predator test裏的naive predator則需要更多的測試.

[Article: Crypsis]Adaptive evolution of Timema according to hostplants

2008-05-06T16:14:00.000+08:00

Adaptive evolution of cryptic coloration: the shape of host plants and dorsal stripes in Timema walking-sticks

¹Marine Science Institute, University of California, Santa Barbara, CA 93106, USA
²Behavioural Ecology Research Group, Department of Biosciences, Simon Fraser University, Burnaby, B. C. V5A 1S6, Canada

*E-mail: sandoval@lifesci.ucsb.edu

Abstract

The adaptive significance of cryptic colour patterns has seldom been analysed in a phylogenetic context. We mapped data on the presence vs. absence of dorsal stripes, and the use of needle-like vs. broad foliage, onto a recent phylogeny of Timema walking-sticks, in order to infer the evolutionary history of these traits and test the hypothesis that the dorsal stripe is an adaptation for crypsis on needle-like leaves. By maximum parsimony optimization, the dorsal stripe has evolved five or six times in this clade, each time in association with the use of vegetation with needle-like leaves. Maddison's concentrated changes test showed that this association between morphology and habitat was statistically significant. By contrast, results based on Pagel's maximum likelihood analyses did not reach significance, probably because the large number of origins of dorsal stripe introduces statistical uncertainty. These results suggest that the adaptations for crypsis can arise readily and in parallel, in the appropriate selective environment. However, they may also constrain the evolution of host-plant use, as there is no unambiguous case of Timema species with dorsal stripes shifting to broad-leaved plants. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 1–5.

See another paper published by Sandoval

[Article: Floral mimicry]Chemical mimicry as a preadaptation

2008-04-30T03:30:00.000+08:00

Evolution of sexual mimicry in the orchid subtribe orchidinae: the role of preadaptations in the attraction of male bees as pollinators

Florian P Schiestl¹ and Salvatore Cozzolino²

¹Institute of Systematic Botany, University of Zürich, Zollikerstrasse 107, CH-8008 Zürich, Switzerland

²Università degli Studi di Napoli "Federico II", Dipartimento delle Scienze Biologiche, Via Foria 223, 80139 Napoli, Italy

author email corresponding author email

BMC Evolutionary Biology 2008, 8:27doi:10.1186/1471-2148-8-27


Published:	28 January 2008

Abstract

Background

Within the astonishing diversity of orchid pollination systems, sexual deception is one of the most stunning. An example is the genus Ophrys, where plants attract male bees as pollinators by mimicking female mating signals. Unsaturated hydrocarbons (alkenes) are often the key signal for this chemical mimicry. Here we investigate the evolution of these key compounds within Orchidinae by mapping their production in flowers of selected species onto their estimated phylogeny.

Results

We found that alkenes, at least in trace amounts, were present in 18 of 20 investigated species together representing 10 genera. Thus, the reconstruction of ancestral state for alkene-production showed that this is a primitive character state in Ophrys, and can be interpreted as a preadaptation for the evolution of sexual deception. Four of the investigated species, namely Ophrys sphegodes, Serapias lingua, S. cordigera, and Anacamptis papilionacea, that are pollinated primarily by male bees, produced significantly larger amounts and a greater number of different alkenes than the species pollinated either primarily by female bees or other insects.

Conclusion

We suggest that high amounts of alkenes evolved for the attraction of primarily male bees as pollinators by sensory exploitation, and discuss possible driving forces for the evolution of pollination by male bees.

[Article]Conflict btw natural & sexual selection due to mmicry

2008-04-30T03:19:00.000+08:00

Interspecific sexual attraction because of convergence in warning colouration: is there a conflict between natural and sexual selection in mimetic species?

Journal of Evolutionary Biology

Volume 21 Issue 3 Page 749-760, May 2008

Citation: C. ESTRADA, C. D. JIGGINS (2008) Interspecific sexual attraction because of convergence in warning colouration: is there a conflict between natural and sexual selection in mimetic species? Journal of Evolutionary Biology 21 (3) , 749–760 doi:10.1111/j.1420-9101.2008.01517.x

Abstract

When species converge in their colour patterns because of mimicry, and those patterns are also used in mate recognition, there is a probability of conflicting selection pressures. Closely related species that mimic one another are particularly likely to face such confusion because of similarities in their courtship behaviour and ecology. We conducted experiments in greenhouse conditions to study interspecific attraction between two mimetic butterfly species, Heliconius erato and Heliconius melpomene. Both species spent considerable time approaching and courting females of the co-mimic species. Experiments using wing models demonstrated the importance of colour pattern in this interspecific attraction. Although males of H. melpomene were attracted to their co-mimics as much as to their own females, H. erato males were more efficient at distinguishing conspecifics, possibly using wing odours. Although preliminary, these results suggest that the use of additional cues may have evolved in H. erato to reduce the cost of convergence in visual signals with H. melpomene. Overall, our results showed that there might be a cost of mimetic convergence because of a reduction in the efficiency of species recognition. Such cost may contribute to explain the apparently stable diversity in Müllerian mimetic patterns in many tropical butterfly assemblages.

[Article: Predation]Predators Make (Temporary) Escape from Coevolutionary Arms Race

2008-03-26T09:45:00.000+08:00

Predators Make (Temporary) Escape from Coevolutionary Arms Race

Liza Gross

Citation: Gross L (2008) Predators Make (Temporary) Escape from Coevolutionary Arms Race. PLoS Biol 6(3): e75 doi:10.1371/journal.pbio.0060075

Published: March 11, 2008

Arguably cute and spanning at most 20 cm from head to tail, the rough-skinned newt packs pretty near the most poisonous punch known to the animal kingdom. Taricha granulosa, like all species in its genus, exudes an exceptionally potent neurotoxin, tetrodotoxin (TTX) from its skin glands. Some Taricha newts could wipe out thousands of mice or a clutch of humans with their toxic issue. But why produce enough poison to kill a potential predator several times over? To discourage the one predator—the common garter snake (Thamnophis sirtalis)—that's resistant enough to the poison to count on newts as a food source.

URL: http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0060075

Phenotypic Mismatches Reveal Escape from Arms-Race Coevolution

Charles T. Hanifin¹^¤^*, Edmund D. Brodie Jr.¹, Edmund D. Brodie III²

1 Department of Biology, Utah State University, Logan, Utah, United States of America, 2 Department of Biology, University of Virginia, Charlottesville, Virginia, United States of America

Because coevolution takes place across a broad scale of time and space, it is virtually impossible to understand its dynamics and trajectories by studying a single pair of interacting populations at one time. Comparing populations across a range of an interaction, especially for long-lived species, can provide insight into these features of coevolution by sampling across a diverse set of conditions and histories. We used measures of prey traits (tetrodotoxin toxicity in newts) and predator traits (tetrodotoxin resistance of snakes) to assess the degree of phenotypic mismatch across the range of their coevolutionary interaction. Geographic patterns of phenotypic exaggeration were similar in prey and predators, with most phenotypically elevated localities occurring along the central Oregon coast and central California. Contrary to expectations, however, these areas of elevated traits did not coincide with the most intense coevolutionary selection. Measures of functional trait mismatch revealed that over one-third of sampled localities were so mismatched that reciprocal selection could not occur given current trait distributions. Estimates of current locality-specific interaction selection gradients confirmed this interpretation. In every case of mismatch, predators were “ahead” of prey in the arms race; the converse escape of prey was never observed. The emergent pattern suggests a dynamic in which interacting species experience reciprocal selection that drives arms-race escalation of both prey and predator phenotypes at a subset of localities across the interaction. This coadaptation proceeds until the evolution of extreme phenotypes by predators, through genes of large effect, allows snakes to, at least temporarily, escape the arms race.

URL: http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0060060

[Team]Jim Mallet (University College London)

2008-03-25T23:12:00.000+08:00

Research themes

Primarily directed towards answering a basic, but still poorly understood riddle: how do new species arise? His group focuses on evolution and ecology of butterflies and moths (Lepidoptera), particularly near the species boundary. The Lepidoptera form 15-20% of the world's described species, yet are poorly known genetically.

(1) Hybridization and evolution in Heliconius butterflies
(2) Taxonomy, mimicry and biogeography in the Ithomiinae

Although his primary interests are in genetic and systematic studies of populations, geographic forms, and speciation, many of his results have obvious implications for conservation of endangered taxa. He remains committed to and interested in topics such as insecticide resistance, safety concerns about the release of genetically modified organisms (GMOs), and in the biodiversity and conservation applications of his work.

URL: http://www.ucl.ac.uk/taxome/jim/

[Article]Juvenile Hormone Regulates Butterfly Larval Pattern Switches

2008-03-25T16:16:00.000+08:00

Abstract:

Juvenile Hormone Regulates Butterfly Larval PatternSwitches

Ryo Futahashi¹^,2 and Haruhiko Fujiwara¹^*

Insect color patterns can be very diverse. This variation isalso seen among many larval instar stages, which can take onvastly different phenotypes. Young caterpillars of the swallowtailbutterfly, Papilio xuthus, are mimics of bird droppings, whereasthe fifth larval instar is camouflaged among the leaves of hostplants (cryptic pattern). We find that juvenile hormone (JH)titers decrease during the fourth larval instar. Furthermore,treatment with JH analog at the beginning of the fourth instarstage resulted in reproducing the mimetic pattern instead ofthe usual cryptic one and likewise altered gene expression patternsto that associated with the mimetic pattern. These findingssuggest that JH regulates the progressive larval pattern switchof this insect.

¹ Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Bioscience Building 501, Kashiwa, Chiba 277-8562, Japan.
² National Institute of Agrobiological Sciences, 1-2 Owashi, Tsukuba, Ibaraki 305-8634, Japan.

^* To whom correspondence should be addressed. E-mail: haruh@k.u-tokyo.ac.jp
URL: http://www.sciencemag.org/cgi/content/full/319/5866/1061?rss=1

[Video]Butterfly wings under UV

2008-03-16T15:48:00.001+08:00

http://youtube.com/watch?v=7rkWeyUURts

[Video]Animal camouflage & mimicry on youtube

2008-03-16T14:58:00.000+08:00

http://youtube.com/watch?v=zC0zOLqYnRg
http://youtube.com/watch?v=7ujRgSRYE9A
http://youtube.com/watch?v=SCgtYWUybIE&feature=related

(第三段影片是焦傳金老師演講時使用過的video clip)

[Article]Can experienced birds select for Müllerian mimicry?

2008-03-14T10:59:00.000+08:00

link: http://tinyurl.com/2m6zlz
Ihalainen, E. et al. 2008. Behav. Ecol. 19: 362-368
Abstract: Field experiments have shown that avian predators in the wild can select for similarity of warning signals in aposematic prey (Müllerian mimicry) because a common signal is better protected than a signal that is novel and rare. The original theory of Müllerian mimicry assumes that the mechanism promoting mimicry is predator learning; by sharing a signal, the comimic species share the mortality that is due to sampling by inexperienced predators. Predation events have not been observed in the wild, and learning experiments with naive bird predators in a laboratory have not unambiguously shown a benefit of a uniform signal compared with different signals. As predators in the field experiments are likely to be more experienced compared with previous laboratory experiments, we studied selection by experienced predators on a novel imperfect mimic. We trained great tits Parus major to avoid artificial aposematic models and subsequently introduced perfect and imperfect mimics at different frequencies. Birds with prior experience on the models selected against the imperfect mimics that were at a disadvantage also in a memory test conducted a week after their introduction. Selection against the imperfect mimics was antiapostatic. However, the imperfect mimics also benefited from some signal generalization to the models and possibly gained protection because the birds were familiar with the alternative cryptic prey that was also present. Our results suggest that experienced predators might be more important to the evolution of mimicry than the learning-based theory assumes.

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

2008-03-13T13:29:00.000+08:00

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.

[Article]Cognitive Dimensions of Predator Responses to Imperfect Mimicry

2008-03-13T11:51:00.000+08:00

Link: http://0rz.tw/633Np
Abstract: Many palatable animals, for example hoverflies, deter predators by mimicking well-defended insects such as wasps. However, for human observers, these flies often seem to be little better than caricatures of wasps—their visual appearance and behaviour are easily distinguishable from those which they are attempting to mimic. This imperfect mimicry baffles evolutionary biologists, because one might expect natural selection to do a more thorough job. Here we discuss two types of cognitive processes that might explain why distinguishable mimics could enjoy increased protection from predation. Speed–accuracy tradeoffs in predator decision making might give imperfect mimics sufficient time to escape, and predators under time constraint might avoid time-consuming discriminations between well-defended models and inaccurate edible mimics and instead adopt a “safety first” policy of avoiding insects with similar appearance. Categorisation of prey types by predators could mean that wholly dissimilar mimics may be protected, provided they share some common property with noxious prey. If predators use experience with multiple prey types to learn rules rather than just memorising the appearance of individual prey types, it follows that different individual predators should form different categories, each including separate types of novel prey. Experimental studies to test these hypotheses should be straightforward, because we can use the relatively simple signals (e.g., striped patterns) with which prey manipulate predator behaviour as tools for investigating cognitive processes that underlie decision making and object recognition in animals' daily lives.