北美的貝氏擬態的蠑螈顯示擬態者也能影響擬態系統的演化方向
photo from Eastern newt (wiki), 貝氏擬態模型
摘要
Conspicuousness, or having high contrast relative to the surrounding back- ground, is a common feature of unpalatable species. Several hypotheses have been proposed to explain the occurrence of conspicuousness, and while most involve the role of conspicuousness as a direct signal of unpalat- ability to potential predators, one hypothesis suggests that exaggerated conspicuousness may evolve in unpalatable species to reduce predator confusion with palatable species (potential Batesian mimics). This hypothesis of antagonistic coevolution between palatable and unpalatable species hinges on the ‘cost of conspicuousness’, in which conspicuousness increases the likelihood of predation more in palatable species than in unpalatable species. Under this mimicry scenario, four patterns are expected: (i) mimics will more closely resemble local models than models from other localities, (ii) there will be a positive relationship between mimic and model conspicuousness, (iii) models will be more conspicuous in the presence of mimics, and (iv) when models and mimics differ in conspicuousness, mimics will be less conspicuous than models. We tested these predictions in the salamander mimicry system involving Notophthalmus viridescens (model) and one colour morph of Plethodon cinereus (mimic). All predictions were supported, indicating that selection for Batesian mimicry not only influences the evolution of mimics, but also the evolution of the models they resemble. These findings indicate that mimicry plays a large role in the evolution of model warning signals, particularly influencing the evolution of conspicuousness.
貝氏擬態的演化預期是mimic會單方向追著model的斑紋跑，而穆氏擬態的是則是兩方共同趨近，因此在貝氏擬態的系統中，model應該總是會比起mimic更加顯眼，而非轉向趨近與mimic的相似。
這個研究的立論就在於此，作者藉由火焰蠑螈 (Notophthalmus viridescens)與其貝氏擬態者紅背蠑螈 (Plethodon cinereus)討論這個問題。作者提出四個假設 1) mimic與當地的model相似度較高 2) mimic與model的明顯度會有正相關 3) model比起mimic會比較明顯 4) 若兩者間明顯度有差異，mimic的明顯度必然低於model。藉由量測反射光譜與視覺模型的套用，結果支持上面的四個預期假設。
photo from red-bakced salamander (wiki)
紅背蠑螈似乎是多態型的種類，圖為沒有紅背的個體
整體來說就是model會影響mimic，反過來mimic也會影響model，這個共通點似乎在貝氏擬態與穆氏擬態都是是用的。
另一個小問題，這兩種蠑螈個人覺得不是很相像，是某種不完美擬態嗎？還是只是單純的兩種都有類似的訊號，剛好其中一種難吃？
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