Using phylogenetic information to predict species tolerances to toxic chemicals

Tolerance to toxic substances is a characteristic of an organism that determines whether it is able to withstand the concentrations occurring in its environment. The measurement of tolerance is therefore of fundamental importance when assessing the impact of anthropogenic chemicals on ecosystems and ecological communities. Although an appreciable amount of information on species tolerance to chemicals has been collected through the last 50 years, substantial gaps remain in our knowledge of tolerance relative to the diversity of organisms inhabiting aquatic ecosystems and the great and increasing number of chemicals released in these ecosystems. Within that context, methods allowing one to reliably and accurately estimate a species' tolerance using other known characteristics would be valuable. In the present study we introduce an approach that uses phylogeny to estimate the tolerance of a species using that of a set of other species related to the focus species at different phylogenetic scales. We estimated phylogenies from molecular data (DNA sequences) or inferred them from taxonomy. Up to 83% of the among-species variation in tolerance (log-transformed median lethal concentration over 96 hours; LC50) was found to be phylogenetically structured and was therefore usable for making predictions. The ability of phylogenetic models to produce accurate estimates of species tolerances is apparently related to the availability of information within species groups and the variation in pesticide tolerance within these groups. Toxicity models integrating phylogeny therefore appear suitable to assist in risk assessment.