Evolutionary biology of plant defenses against herbivory and their predictive implications for endocrine disruptor susceptibility in vertebrates

Hormone disruption is a major, underappreciated component of the plant chem ical arsenal, and the historical coevolution between hormone-disrupting pla nes and herbivores will have both increased the susceptibility of carnivore s and diversified the sensitivities of herbivores to manmade endocrine disr upters. Here I review diverse evidence of the influence of plant secondary compounds on vertebrate reproduction, including human reproduction. Three o f the testable hypotheses about the evolutionary responses of vertebrate he rbivores to hormone-disrupting challenges from their diet are developed. Sp ecifically, the hypotheses are that a) vertebrate herbivores will express s teroid hormone receptors in the buccal cavity and/or the vomeronasal organ; b) absolute sex steroid concentrations will be lower in carnivores than in herbivores; and c) herbivore steroid receptors should be more diverse in t heir binding affinities than carnivore lineages. The argument developed in this review, if empirically validated by support for the specific hypothese s, suggests that a) carnivores will be more susceptible than herbivores to endocrine-disrupting compounds of anthropogenic origin entering their bodie s, and b) diverse herbivore lineages will be variably susceptible to any gi ven natural or synthetic contaminant. As screening methods for hormone-disr upting potential are compared and adopted, comparative endocrine physiology research is urgently needed to develop models that predict the broad appli cability of those screening results in diverse vertebrate species.