Effects of freshwater salinization and biotic stressors on amphibian morphology

Organisms are commonly exposed to numerous stressors that induce behavioral, physiological, or morphological changes in some combination. In northern temperate latitudes, de-icing agents are a major stressor to species in freshwater ecosystems (primarily sodium chloride; NaCl). Species-specific responses to road salt toxicity range from lethal to sublethal effects, but it remains unclear how these effects interact with biotic stressors. Morphology can be quite sensitive to environmental changes, yet we know little about how it is affected by road salt exposure. We exposed wood frog tadpoles (Rana sylvatica) to two road salt formulations (NaCl and a mixture of NaCl, MgCl2, and KCl), each at three concentrations (200, 600, and 1000 mg Cl-/L), crossed with three biotic stressor levels (predator cue, competition, and a no-stressor control). We then measured the impacts on relative morphology (snout-vent length, body width, forelimb length, forelimb width, hindlimb length, hindlimb width) of...