Comparative analysis of toxicity sensitivity and functional traits in fish

Aquatic ecosystems are heavily affected by anthropogenic pollution. However, our inability to predict toxicity of emerging pollutants in a wide range of aquatic organisms, outside the standard laboratory toxicity testing, hinders the potential for preventing negative impacts from exposure. It has been suggested that the phylogenetic signal for toxicant sensitivity may be low. Here we suggest that the reason for this is that closely related species can demonstrate marked differences in pollution sensitivity. In the largest comparative study on fish sensitivity to chemicals conducted so far, we extracted LC50 data in 269 fish species and 29 environmentally prioritised chemicals from the ECOTOX database, in addition to anatomical, ecological and life history traits from other data sources. We found that phylogenetic signal for sensitivity was low, with closely related species differing markedly in sensitivity. From ecological and life history traits that we tested; maximum length, migration type, habitat salinity and the ability to air-breathe were linked with toxicant sensitivity, but only if phylogeny was not accounted for. Based on these results, we suggest that tolerance and sensitivity to toxicants can evolve as an arbitrary side effect to microevolutionary changes that allow closely related species to diverge and adapt to different ecological niches and life history strategies.