Franks Daniel W, Noble Jason
Biosystems Group, School of Computing, University of Leeds, Leeds LS2 9JT, UK.
Proc Biol Sci. 2004 Sep 7;271(1550):1859-65. doi: 10.1098/rspb.2004.2795.
Theories of the evolution of warning signals are typically expressed using analytic and computational models, most of which attribute aspects of predator psychology as the key factors facilitating the evolution of warning signals. Sherratt provides a novel and promising perspective with a model that considers the coevolution of predator and prey populations, showing how predators may develop a bias towards attacking cryptic prey in preference to conspicuous prey. Here, we replicate the model as an individual-based simulation and find, in accordance with Sherratt, that predators evolve a bias towards attacking cryptic prey. We then use a Monte Carlo simulation to calculate the relative survivorships of cryptic and conspicuous prey and stress that, as it stands, the model does not predict the evolution or stability of warning signals. We extend the model by giving predators continuous attack strategies and by allowing the evolution of prey conspicuousness: results are robust to the first modification but, in all cases, cryptic prey always enjoy a higher survivorship than conspicuous prey. When conspicuousness is allowed to evolve, prey quickly evolve towards crypsis, even when runaway coevolution is enabled. Sherratt's approach is promising, but other aspects of predator psychology, besides their innate response, remain vital to our understanding of warning signals.
警示信号进化理论通常用分析模型和计算模型来表述，其中大多数将捕食者心理的各个方面视为促进警示信号进化的关键因素。谢拉特提出了一个新颖且有前景的观点，他的模型考虑了捕食者和猎物种群的共同进化，展示了捕食者如何可能形成一种偏好，即相较于显眼的猎物，更倾向于攻击伪装的猎物。在此，我们将该模型复制为基于个体的模拟，并且如谢拉特所发现的那样，捕食者进化出了攻击伪装猎物的偏好。然后，我们使用蒙特卡罗模拟来计算伪装猎物和显眼猎物的相对存活率，并强调就目前而言，该模型无法预测警示信号的进化或稳定性。我们通过赋予捕食者连续的攻击策略以及允许猎物显眼性的进化来扩展该模型：结果对于第一种修改是稳健的，但在所有情况下，伪装猎物的存活率总是高于显眼猎物。当允许显眼性进化时，即使启用了失控的共同进化，猎物也会迅速进化为伪装状态。谢拉特的方法很有前景，但除了它们的先天反应之外，捕食者心理的其他方面对于我们理解警示信号仍然至关重要。
