Collaborative Research: Evolutionary Costs of Exploiting Poisonous Prey

许多进化变化理论的一个关键观点是，适应是有“代价”的：一种性状适应能力的增强必然会限制其他性状适应能力的增强。适应成本或进化权衡的一种方式被认为是通过共同进化的相互作用产生的。代表了许多代相互选择的捕食者-猎物系统是检验这种权衡进化解释的理想情况。只有一个自然的捕食者-猎物系统提供了种群水平的证据，表明由于猎物的反捕食者适应性而提高了利用猎物的能力。Taricha属蝾螈出现在美国西海岸，产生神经毒素河豚毒素（TTX），这是已知最有效的神经毒素之一。唯一已知的对这种毒素有抵抗力的捕食者是与蝾螈一起生活并以蝾螈为食的Thamnophis sirtalis。蛇类种群对TTX的抗性存在显著差异，在抗性种群中，初步证据表明运动能力下降伴随着对TTX的抗性增加。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难得的机会。这项研究将检查在抗性和非抗性的吊带蛇种群中适应的潜在成本。将在每个种群中研究运动表现和TTX抗性，并使用这些特征之间的相关性来评估权衡。将构建描述种群之间进化关系的系统发育，并用于检查抗性的历史演变以及抗性与性能之间的权衡。这种方法将允许对权衡进化的替代解释进行测试。研究TTX耐药性的进化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.