Speed Michael P, Ruxton Graeme D
School of Biological Sciences, University of Liverpool, Liverpool L69 7ZB, UK.
Proc Biol Sci. 2005 Feb 22;272(1561):431-8. doi: 10.1098/rspb.2004.2968.
The evolution of aposematism is considered to be a major evolutionary problem because if new aposematic forms emerged in defended cryptic populations, they would face the dual problems of rarity and conspicuousness. We argue that this commonly assumed starting point might not have wide validity. We describe a novel evolutionary computer model in which prey evolve secondary defences and become conspicuous by moving widely over a visually heterogeneous habitat. Unless crypsis imposes high opportunity costs (for instance, preventing prey from efficient foraging, thermoregulation and communication), costly secondary defences are not predicted to evolve at all. However, when crypsis imposes opportunity costs, prey evolve secondary defences that facilitate raised behavioural conspicuousness as prey exploit opportunities within their environment. Optimal levels of secondary defence and of behavioural conspicuousness increase with population sizes and the costs imposed by crypsis. When prey are already conspicuous by virtue of their behaviours, the evolution of aposematic appearances (bright coloration, etc.) is much easier to explain because aposematic traits add little further costs of conspicuousness, but can bring large benefits.
警戒色的进化被认为是一个主要的进化问题，因为如果新的警戒色形式出现在具有防御能力的隐蔽种群中，它们将面临稀有性和显眼性这两个双重问题。我们认为，这种通常假定的起点可能没有广泛的有效性。我们描述了一种新颖的进化计算机模型，在该模型中，猎物进化出二级防御，并通过在视觉上异质的栖息地中广泛移动而变得显眼。除非隐蔽带来高昂的机会成本（例如，阻止猎物进行高效觅食、体温调节和交流），否则预计根本不会进化出代价高昂的二级防御。然而，当隐蔽带来机会成本时，猎物会进化出二级防御，随着猎物在其环境中利用机会，这种防御会促进行为显眼性的提高。二级防御和行为显眼性的最佳水平会随着种群规模以及隐蔽所带来的成本而增加。当猎物因其行为已经很显眼时，警戒色外观（鲜艳的颜色等）的进化就更容易解释了，因为警戒色特征几乎不会增加显眼性的额外成本，但却能带来巨大的益处。
