Toxicity of dangerous prey: Variation of tetrodotoxin levels within and among populations of the newt Taricha granulosa

The ability to identify and accurately measure traits at the phenotypic int erface of potential coevolutionary interactions is critical in documenting reciprocal evolutionary change between species. We quantify the defensive c hemical trait of a prey species, the newt Taricha granulosa, thought to be part of a coevolutionary arms race. Variation in newt toxicity among popula tions results from variation in levels of the neurotoxin tetrodotoxin (TTX) . Individual variation in TTX levels occurs within populations. Although TT X exists as a family of stereoisomers, only two of these (TTX and 6-epi-TTX ) are likely to be sufficiently toxic and abundant to play a role in the de fensive ecology of the newt.