貓頭鷹蝶的眼紋真的擬態貓頭鷹的眼睛嗎？
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| credit Shutter stock |
摘要
Large conspicuous eyespots on butterfly wings have been shown to deter predators. This has been traditionally explained by mimicry of vertebrate eyes, but recently the classic eye-mimicry hypothesis has been challenged. It is proposed that the conspicuousness of the eyespot, not mimicry, is what causes aversion due to sensory biases, neophobia or sensory overloads. We conducted an experiment to directly test whether the eye-mimicry or the conspicuousness hypothesis better explain eyespot efficacy. We used great tits (Parus major) as model predator, and tested their reaction towards animated images on a computer display. Birds were tested against images of butterflies without eyespots, with natural-looking eyespots, and manipulated spots with the same contrast but reduced resemblance to an eye, as well as images of predators (owls) with and without eyes. We found that mimetic eyespots were as effective as true eyes of owls and more efficient in eliciting an aversive response than modified, less mimetic but equally contrasting eyespots. We conclude that the eye-mimicry hypothesis explains our results better than the conspicuousness hypothesis and is thus likely to be an important mechanism behind the evolution of butterfly eyespots.
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| photo from Fig. 1 |
於是這個研究測試了這個簡單的概念，用來做model的貓頭鷹是花頭鵂鶹(Euuasian pygmy owl, Glaucidium passerinum)，而mimic則是用藍裳貓頭鷹環蝶(Caligo martia)，做了像上圖一樣的操作，然後讓以大山雀進行行為實驗。結果顯示貓頭鷹蝶的眼睛的功用與真正的眼睛有類似的功用，而不單純的只有顯眼性的功用。
這個有趣的是這個假餌是用印出來的，當然這些眼紋的操作就是PS，印出來後就可以簡單的呈現給捕食者看得到結果。但我認為這個研究最大的問題在於環蝶平常野外根本不會這樣展示斑紋，而是像最上面那張圖一樣，折起來只展示半面。不同的展示方式也是眼斑的作用爭議最大的地方，通常會這樣呈現的很多都是標本，野外因為停棲位置或是行為上的限制，很少有機會能把腹面平面展開面對捕食者，也就很難用兩隻眼睛「盯」著捕食者，更不用說捕食者會被嚇到，也因為這樣有其他研究者認為眼斑根本只是某種顯眼的警戒色，而不是眼睛的擬態。
用一個不自然的方式呈現做出來的結果，然後用這個結果說眼斑真的有用，好像有點怪怪的？
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