Collaborative Research: Evolutionary Costs of Exploiting Poisonous Prey

9509295 9521429布罗迪·布罗迪许多进化变化理论的一个关键因素是，适应是有“代价”的：一个性状的适应增加必然会限制其他一些特征的适应增加的潜力。适应成本或进化权衡被认为产生的一种方式是通过共同进化的相互作用。代表许多世代相互选择的捕食者-猎物系统是检验这种对权衡进化的解释的理想情况。只有一个自然捕食者-猎物系统提供了种群水平的证据，表明由于捕食者对猎物的适应，利用猎物的能力增强了。Taricha属的蝾螈生活在美国西海岸，会产生神经毒素河豚毒素(TTX)，这是已知的最有效的神经毒素之一。已知的唯一对这种毒素具有抵抗力的捕食者是与蝾螈一起生活并以其为食的西尔塔尔眼镜蛇(Thamnophim Sirtalis)。蛇类群对TTX的抵抗力有明显差异，初步证据表明，在抗性群体中，运动能力下降伴随着对TTX抵抗力的增强。这一系统为研究与军备竞赛共同进化相关的适应成本提供了一个难得的机会。这项研究将研究抗性和非抗性吊袜带蛇种群适应的潜在成本。将在每个种群中研究运动能力和TTX抗性，并将使用这些特征之间的相关性来评估权衡。将构建一个描述种群之间进化关系的系统发育图，并用它来研究抗性的历史演变以及抗性和性能之间的权衡。这种方法将允许对权衡演变的替代解释进行测试。研究TTX耐药性的演变是了解生物体如何在广泛和危险的天然毒素面前生存的第一步。

9509295 9521429 Brodie Brodie A critical element of many theories of evolutionary change is the idea that there is a "cost" to adaptation: increased adaptation in one trait necessarily restricts the potential for increased adaptation of some other traits. One way that costs of adaptation, or evolutionary tradeoffs, are thought to arise is through coevolutionary interactions. Predator-prey systems that represent many generations of reciprocal selection are ideal situations to test this explanation for the evolution of tradeoffs. Only one natural predator-prey system has provided population level evidence of increased ability to exploit prey evolving as a result of antipredator adaptations in the prey. Newts of the genus Taricha occur along the west coast of the United States and produce the neurotoxin tetrodotoxin (TTX), which is one of the most potent nerve toxins known. The only known predators resistant to this toxin are Thamnophis sirtalis that occur with, and feed on, the newts. Snake populations differ markedly in their resistance to TTX, and within resistant populations there is preliminary evidence suggesting that decreased locomotor performance accompanies increased resistance to TTX. This system provides an exceptional opportunity to study the costs of adaptation associated with arms race coevolution. This research will examine potential costs of adaptation in resistant and nonresistant populations of garter snakes. Locomotor performance and TTX resistance will be studied in each population, and the correlation between these traits will be used to assess tradeoffs. A phylogeny describing the evolutionary relationships between populations will be constructed and used to examine the historical evolution of both resistance and the tradeoff between resistance and performance. This approach will allow tests of alternative explanations for the evolution of tradeoffs. Examining the evolution of resistance to TTX is a first step to understanding how organisms survive in th e face of widespread and dangerous natural toxins.