Limb length and poison glands size as predictors of anti-predatory performance in South American true toads

Abstract

Evolution of anti-predatory strategies is often associated with specific morphological traits that affect escape or fight performance and ultimately determine survival. Accordingly, good morphological predictors of performance enable inferences of phenotypic evolution in the context of anti-predatory responses. In this study, we evaluated relationships between morphology and performance in South American true toads of Rhinella considering two anti-predatory strategies described for the genus: active escape and chemical defense. Data on morphology, jumping performance and volume of released poison were obtained for 11 Rhinella lineages, and relationships were tested using phylogenetic methods. We identified that the volume of poison released increases with the area of poison glands, and relative hindlimb length is a good predictor of the relative distance jumped. Ancestral reconstructions of performance traits (jumping distance and poison volume) suggest that some Rhinella lineages specialized in one of these anti-predatory strategies (either escaping or producing large amounts of poison), a result that stimulates future studies addressing evolutionary relationships between morphology, ecology and anti-predatory responses in true toads.