珊瑚礁魚類同時具有貝氏-侵略擬態功用的斑紋來自於多重的天擇壓力
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| 文中的擬態者 勞旦橫口鳚 (Plagiotremus laudandus) photo from Dianne J. Bray, 2011, Bicolor Fangblenny, Plagiotremus laudandus, in Fishes of Australia |
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| 文章中的被擬態者，金鰭稀棘䲁 (Meiacanthus atrodorsalis) photo: Dianne J. Bray, 2011, Eyelash Fangblenny, Meiacanthus atrodorsalis, in Fishes of Australia, accessed 31 Mar 2016 |
標題：Multiple selective pressures apply to a coral reef fish mimic: a case of Batesian-aggressive mimicry.
摘要
Mimics closely resemble unrelated species to avoid predation, capture prey or gain access to hosts or reproductive opportunities. However, the classification of mimicry systems into three established evolutionary mechanisms (protection, reproduction and foraging) can be contentious because multiple benefits may be gained by mimics, causing the evolution of such systems to be driven by more than one selective agent. However, data on such systems are generally speculative or anecdotal. This study provides empirical evidence that dual benefits apply to a coral reef fish mimic in terms of increased access to food (aggressive mimicry) and reduced predation risk (Batesian mimicry). Bicolour fangblennies Plagiotremus laudandus gained access to more reef fish victims, which they attack to feed on fins and scales, when they spent more time associated with their model Meiacanthus atrodorsalis. Furthermore, exact replicas of P. laudandus incurred fewer approaches from potential predators compared with control replicas that varied in resemblance to P. laudandus. Predators with trichromatic visual systems (three distinct spectral sensitivities) could potentially distinguish between replicas based on colour based on theoretical vision models. Therefore, this mimicry system could be best described as Batesian–aggressive mimicry in which mimicry evolution is driven by multiple simultaneous selective pressures.
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photo from Fig. 1
a) i. 金鰭稀棘鳚 (Meiacanthus atrodorsalis) ii. 勞旦橫口鳚 (Plagiotremus laudandus)b) 三種手工實驗用假魚與控制組物種粗吻橫口鳚 (P. rhinorhynchos) |
這個研究地點在印尼蘇拉維西東南方的10個珊瑚礁，這個系統是兩種珊瑚礁魚類，勞旦橫口鳚 (Plagiotremus laudandus)藉由擬態金鰭稀棘鳚 (Meiacanthus atrodorsalis)，跟著這個魚群游來游去，到處偷吃別種魚的鰭或鱗片，是一個典型的侵略型擬態的例子。可是，金鰭稀棘鳚是一個有毒牙的物種，一般的捕食者通常看到這種魚會避開避免攻擊，若是不小心吃到也會吐掉，那麼勞旦橫口鳚通常跟金鰭稀棘鳚游在一起，會不會藉著的關係，在貝氏擬態的保護關係中呢？
作者的實驗分為兩個部分，一個是在那10個珊瑚礁樣區潛水，在海下2-18公尺的地方尋找這些物種，觀察勞旦橫口鳚的攻擊次數與攻擊成功次數，以及勞旦橫口鳚留在金鰭稀棘鳚周圍30公分的時間；另一個部分是利用上圖的四種假餌，包含原樣，兩種變異與一種控制組，每個假魚會放出10分鐘，看看會不會有其他捕食性魚類來攻擊，樣區選擇三種，沒model/有mimic (Lizard island)，有model/有mimic (Lizard island)，有model/有mimic (Pulau Hoga)，並且記錄靠近假魚的其他魚類是捕食性或是非捕食性。
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| photo from Fig. 2 此圖說明model/mimic比例的高低與攻擊成功率無關（黑圈圈），但花在model旁邊時間越多，成功率較高（白鑽石） |
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| photo from Fig. 3 左邊是捕食性魚類，右邊是非捕食性魚類 從上而下分別是三組：沒model/有mimic (Lizard island)，有model/有mimic (Lizard island)，有model/有mimic (Pulau Hoga) |
結果顯示花越多時間在金鰭稀棘鳚旁邊的勞旦橫口鳚個體，偷吃到其他魚類的成功率較高；而在兩種魚類共存的區域，捕食性魚類避開勞旦橫口鳚假魚的數量顯著的比較高，但非捕食性魚類就沒有顯著的差異，支持勞旦橫口鳚的擬態體色同時具有貝氏擬態與侵略性擬態的功用，代表這種魚可能同時承受複雜的天擇壓力。
比起透過飼養的幼雛，或是調控人工假餌來避免野外經驗影響實驗結果，這個研究的一部分是在自然環境下進行的實驗，而且明顯依賴野外捕食者的經驗來支持其結果，雖然說水下的環境與陸地差異很大，可能有更多科學家缺少考慮的因子，但我想這還是比較能夠真實的反應自然界對擬態物種的選擇。
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