耗能低的偽裝也可以很有效嗎？

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?

[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。

演化的軍備競賽─紅皇后與有性生殖

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？

[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。

無翅紅蝽警戒色對捕食者的影響

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。

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

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

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