悠閒的演化出警戒色吧!經由雙向協同選擇理論解釋警戒色的演化起源


photo from Amateru Entomologists' Society
標題:Evolving détente: the origin of warning signals via concurrent reciprocal selection.

摘要

Casualties and impediments inflicted on consumers by defended prey, and vice versa, may be averted by vocalizations, postures, coloration, scents, and other warning, or so-called aposematic, displays. The existence of aposematic signals has challenged biologists who have sought plausible mechanisms for their evolution. Here, we elaborate on the rationale for the hypothesis that aposematic signals arise via concurrent reciprocal selection (CRS) enacted between inimical signal receivers and signal emitters, where signal emitters, e.g., defended prey, select against non-discriminating signal receivers, e.g., predators, and signal receivers select against unrecognized signal emitters. It is postulated that this mutual selective interaction culminates in the survival of discriminating signal receivers that avoid signal emitters, and recognized (distinctive) signal emitters that are avoided by signal receivers. A CRS hypothesis for the evolution of aposematism, therefore, maintains that distinctive features of prey arise in response to selection imposed by consumers, and that avoidances of those features by consumers arise in response to selection imposed by defended prey. We discuss the plausible inception of aposematism via CRS in light of related hypotheses, and describe points of concordance with previous observations and suggestions on the origin of aposematism. Aposematism arising via CRS is not contingent upon the relatedness of signallers, aversions acquired by learning, or other conditions postulated for some other evolutionary hypotheses. CRS is a credible alternative hypothesis for the evolution of warning signals in diverse consumer-prey interactions.

關於警戒色演化上怎麼冒出來的一直是件很奇怪的事。簡單的說,一個物種如果變的顯眼但能吃,捕食者很快就發現這能吃;反過來, 如果物種變的顯眼前先變的不能吃,那麼捕食者學的起來嗎?還是連結的是變顯眼前的顏色?如果這樣還需要的顯眼嗎?還要考慮各種捕食者與被捕食者間的因子與連結,造就各式各樣的對於警戒色演化上的假設,但各自有道理,到現在也沒個定論。

這篇文章整理了一個整合訊號接收者與訊號發出者間關係的理論,稱為concurrent reciprocal selection (CRS),大致上是說不管是從哪個角色出發,發出訊號者會傾向留下能認得訊號的接收者,認不得的會被篩選掉,而接收者會傾向把能辨識的發出者留下,分不出來或難以辨識的會被篩選掉,形成一個同時間互相篩選協調的機制。(細節詳見內文)

CRS對警戒色的演化理論示意圖
photo from Fig. 1
通常理論發展出來,大多是單方面的對訊號發出者篩選,變化也是發出者在變化,可是這篇加入訊號接收者在選汰上的角色,而非單純討論哪些心理因子可能對演化有影響,而是認為這是一個雙向的機制,的確是與先前發展的理論不盡相同。這個理論聽起來當然也是很理想(每個理論看起來都很理想),也提供我們對於警戒性的演化新的思考方向。

有機會來整理一下所有關於警戒色演化的理論好了。

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