複合斑紋的擬態中，個別斑紋突出度是否影響擬態物種間斑紋的準確度？
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| photo from content |
標題：Multi-trait mimicry and the relative salience of individual traits
摘要
Mimicry occurs when one species gains protection from predators by resembling an unprofitable model species. The degree of mimic–model similarity is variable in nature and is closely related to the number of traits that the mimic shares with its model. Here, we experimentally test the hypothesis that the relative salience of traits, as perceived by a predator, is an important determinant of the degree of mimic–model similarity required for successful mimicry. We manipulated the relative salience of the traits of a two-trait artificial model prey, and subsequently tested the survival of mimics of the different traits. The unrewarded model prey had two colour traits, black and blue, and the rewarded prey had two combinations of green, brown and grey shades. Blue tits were used as predators. We found that the birds perceived the black and blue traits to be similarly salient in one treatment, and mimic–model similarity in both traits was then required for high mimic success. In a second treatment, the blue trait was the most salient trait, and mimic–model similarity in this trait alone achieved high success. Our results thus support the idea that similar salience of model traits can explain the occurrence of multi-trait mimicry.
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| photo from The Haunted Pen |
這個研究利用人工的模型，與藍山雀做為捕食者討論這個問題。作者設定的警戒色是「藍＋黑」，選擇藍色是為了避免藍山雀因為以前的經驗影響實驗結果。實驗設計如上圖，主要分為兩個部分，一個測試整體認知，一個測試顏色突出認知，其中設計以藍色是最為明顯的顏色，兩個部分都有1對1與1對多的設計。第一個結果顯示mimic的對比度與「藍+黑」最接近的最為成功，第二個結果顯示對比度與藍色最接近的最成功。這證據支持mimic的顏色突出度必須與model接近才有可能降低天擇的選汰。
如果這樣就有趣了，意思就是mimic的斑紋演化上來說，無法先變出A部分再變出B部分，看起來是必須整體同時出現，也就是題目所說的「複合式」斑紋。那麼如果不是像毒蝶那樣可以透過基因滲透傳遞性狀的族群，要如何一次性的出現相似的斑紋呢？這個研究的結果是不是比較支持「兩步演化」理論（two-step theory）呢？
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