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

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Evidence for arms-race coevolution between predator and prey will beevaluated in a unique natural interaction between toxic newts and theirresistant snake predators. Newts possess the neurotoxin tetrodotoxin(TTX), which blocks sodium channels in nerves and muscles. No knownpredator can ingest TTX and survive except for garter snakes of thegenus Thamnophis. Previous work demonstrated that predator and prey havematched levels of defensive and exploitative abilities, but the sourceof newt toxicity is still unknown. High Performance LiquidChromatography (HPLC) will be used to assay levels of toxin inlaboratory bred and reared newts to determine whether the requisiteindividual, genetic and population variation exists for newts to evolvein response to predators, allowing an evaluation of whether observedpatterns of matching are consistent with an arms race view ofcoevolution. Understanding the interactions between species that drivecoevolution is a major goal of evolutionary biology. Coevolution, inwhich one species evolves in response to another species, is thought tobe one of the major engines of biodiversity. Although coevolution isthought to be a common outcome of many ecological interaction, there arestrong theoretical and empirical reasons to suspect that predator-preyinteractions might be different. This research will shed important lighton natural variation in an important neurotoxin, TTX, which is usedwidely in studies of nerve function and development, by identifying thesources of TTX in amphibians.