Life-history trait variation in tadpoles of the warty toad in response to pond drying

Abstract

We explored the response to habitat desiccation in tadpoles of the warty toad Rhinella spinulosa in a manipulative field experiment. We built an artificial pond system with two desiccation levels (high and low) and populated with tadpoles at Gosner stage 25. Each treatment was replicated six times. We measured the survival, size and age at metamorphosis, development rate and hind limb length in metamorphs. The results showed that tadpoles from the high desiccation ponds accelerated their development, reaching metamorphosis at an earlier age than tadpoles from the low desiccation ponds. Survival, size at metamorphosis and hind limb length were not different between treatments. This experiment demonstrated that tadpoles of R. spinulosa accelerate their development in response to habitat desiccation. Such plasticity may allow them to avoid mortality in short duration ponds. No evidence for a trade-off between development time and size at metamorphosis was found in this experiment. We suggest that factors such as initial tadpole density and nutritional quality of food would contribute towards determining whether metamorphosis occurs at the developmental threshold or at a larger size.