鳥類捕食者的眼中看起來，擬態的獵物真的都很像嗎？

標題：Prey from the eyes of predators: Color discriminability of aposematic and mimetic butterflies from an avian visual perspectives

摘要

Predation exerts strong selection on mimetic butterfly wing color patterns, which also serve other functions such as sexual selection. Therefore, specific selection pressures may affect the sexes and signal components differentially.We tested three predictions about the evolution of mimetic resemblance by comparing wing coloration of aposematic butterflies and their Batesian mimics: (a) females gain greater mimetic advantage than males and therefore are better mimics, (b) due to intersexual genetic correlations, sexually monomorphic mimics are better mimics than female-limited mimics, and (c) mimetic resemblance is better on the dorsal wing surface that is visible to predators in flight. Using a physiological model of avian color vision, we quantified mimetic resemblance from predators’ perspective, which showed that female butterflies were better mimics than males. Mimetic resemblance in female- limited mimics was comparable to that in sexually monomorphic mimics, suggesting that intersexual genetic correlations did not constrain adaptive response to selection for female-limited mimicry. Mimetic resemblance on the ventral wing surface was better than that on the dorsal wing surface, implying stronger natural and sexual selection on ventral and dorsal surfaces, respectively. These results suggest that mimetic resemblance in butterfly mimicry rings has evolved under various selective pressures acting in a sex- and wing surface-specific manner.

這篇的中心思想就想要測試三個假設 1) 雌性擬態的精確度比雄性好 2) 單型性擬態的比雌性擬態的物種精確 3) 擬態斑紋在背面的比在腹面的精確。作者想要知道這些現象是不是普遍存在於擬態的蝴蝶中，於是想說「如果從鳥類的視覺來看的話，會不會有差異呢？。」，就用了測量標本的反射光譜，得到某些數據，然後套入鳥類的視覺模型來看看這些擬態的蝴蝶會不會有差異。整個概念就是當把得到的數據套入模型後，比較model與mimic得到的結果，然後統計有沒有顯著差異。結果顯示雌性的擬態比雄性精確，雌性擬態與單型性的物種相比無差異，在背側斑紋比在腹側斑紋精確。

這個結果的確顯示了某些選汰壓力的作用方向，但這個文章中應該只是要展現這有某種演化趨勢，可是缺少考量某些多態型的物種（如大鳳蝶），或是不同的物種在自然界中行為的差異，或許會導向不同的結果與解釋。