擬態生物學

標題：A test of fundamental questions in mimicry theory using long-term datasets

摘要

Since the phenomenon of mimicry was first described by Bates in 1862 it has become one of the foundational examples of adaptive evolution. Numerous subcategories of mimicry and dozens of hypotheses pertaining to its evolution and maintenance have been proposed. Many of these hypotheses, however, are difficult to test in experimental settings, and data from natural observations are often inadequate. Here we use data from a long-term survey of butterfly presence and abundance to test several hypotheses pertaining to Batesian and female-limited polymorphic mimicry (FPM; a special case of Batesian mimicry). We found strong evidence that models outnumber mimics in both mimicry systems, but no evidence for an increase in relative abundance of FPM mimics to their Batesian counterparts. Tests of the early-emergence/model first hypothesis showed strong evidence that the Batesian mimic routinely emerges after the model, while emergence timing in the FPM system was site specific, suggesting that other ecological factors are at play. These results demonstrate the importance of long-term field observations for testing evolutionary and ecological hypotheses.

如果擬態群在自然的情況下是有效的，那麼這個擬態群可能符合一些基本的前提，像是model比起mimic來說數量較多、比較難吃、時序上比較早出現等等，都是這個擬態群「應該」要符合的。雖說如此，能夠支持這些基本假設的證據卻是少之又少，也就代表這些基本的假設究竟是科學家自己的想像，還是真正發生在自然界呢？

這個研究透過累積十年的蝴蝶記錄資料來探討這個問題，資料記錄的地點在北美洲，分別是Gates Canyon、Washington與Lang Crossing（詳細資訊見butterfly.ucdavis.edu），記錄的時間大約是每14天一次，累積了1999-2010間的資料。

他們想要討論的問題在於如果貝氏擬態的mimic太多，會導致整個系統的保護作用降低或失效，因此mimic絕對不能比model還多，因此一個可能性就是「model在自然界中絕對數量比mimic多」，另一個可能性是如果mimic只有其中一個性別擬態，那麼相對來說mimic的數量也會減少，因此他們選了兩個系統，其中一個是代表貝氏擬態的系統，Adelpha californica (model)與Limenitis lorquinii (mimic)（見上圖），另一個是雌性擬態的系統（見下圖）。

結果顯示兩個系統中，model的數量都遠多於mimic。發生的時序上來說，貝氏擬態的mimic出現時序都晚於其model，而雌性擬態的物種出現則局現在某幾個地方，可能有其他的生態因子限制其分佈。