Collaborative Research: Independent Evolutionary Origins of Tetrodotoxin Resistance as a Test of the Geographic Mosaic of Coevolution

拟议的研究将调查地理结构在确定共同进化相互作用模式和军备竞赛动态方面的作用。过去很难将生物地理结构本身与种群之间的环境差异分开，因为研究系统不能在相同的地理范围内复制。Thamnophis属的吊带蛇和Taricha属的毒蝾螈之间的军备竞赛为探索这个问题提供了一个独特的机会，因为新的证据表明，对相互作用至关重要的特征有多个独立的进化起源。拟议的研究将确定在多种吊带蛇和蝾螈发生的地区河豚毒素毒性和钠通道抗性变化的大范围地理格局。如果地理和/或猎物表型是决定共同进化轨迹的最重要因素，那么同域的吊带蛇种群将显示出匹配的抗性水平。如果选择环境或物种相互作用的差异是最重要的，那么同域食肉动物种群将具有无与伦比的抵抗力。通过调查同域捕食者的饮食组成和各捕食者与被捕食者之间的表型匹配程度，可以进一步确定影响同域捕食者表型不匹配的一般因素。揭示共同进化的基本方面对于进一步理解所有生物相互作用至关重要，无论是人类与病原体、疾病与抗生素，还是捕食者与猎物之间的相互作用。这个项目探讨了影响所有系统的共同进化过程的基本要素。拟议的资金将直接支持培训两名研究生担任研究助理，以及许多其他研究生和本科生，他们在各个层次上参与该项目。蛇-蝾螈军备竞赛已经发展成为一种流行的范例，通过外展教育来理解共同进化（在最近的PBS-TV，大众媒体，以及即将在印第安纳州布卢明顿的Wonderlab儿童科学博物馆举办的展览上）。

The proposed research will investigate the role of geographic structure in determining patterns of coevolutionary interaction and the dynamics of arms-races. It has been difficult in the past to disentangle biogeographic structure itself from the environmental differences among populations because study systems cannot be replicated within the same geographic range. The arms race between garter snakes of the genus Thamnophis and toxic newts of the genus Taricha provides a unique opportunity to explore this problem because new evidence indicates multiple independent evolutionary origins of the traits critical to the interaction. The proposed research will determine the broad-scale geographic patterns of variation in tetrodotoxin toxicity and sodium channel resistance in regions where multiple species of garter snakes and newts occur. If geography and/or prey phenotypes are most important in determining coevolutionary trajectories, sympatric populations of garter snakes will show matched levels of resistance. If differences in the selective environment or species interactions are paramount, then sympatric populations of predators will have unmatched levels of resistance. By surveying diet composition in sympatric predators and the degree of phenotype matching between each predator and prey species, the investigators can further determine the general factors influencing mismatches among sympatric predators. Revealing the fundamental aspects of coevolution is critical to furthering our understanding of all biological interactions, whether they occur between humans and pathogens, disease and antibiotics, or predators and prey. This project explores basic elements of the coevolutionary process that impact all systems. The proposed funding will directly support the training of two graduate students as research assistants as well as numerous other graduate and undergraduate students that are involved with the project at all levels. The snake-newt arms race has developed as a popular paradigm for understanding coevolution through outreach education (on recent PBS-TV, popular press, and a coming exhibit in the Wonderlab children's science museum in Bloomington, IN).