Limited thermal plasticity and high mortality in Pithecopus gonzagai (Phyllomedusidae): implications for tropical amphibians under climate change

Temperature is a key abiotic factor influencing the development and survival of ectothermic animals. Amphibians, especially those from tropical regions, are considered highly vulnerable to climate change due to their limited acclimation capacity. In this study, we evaluated the effects of thermal acclimation on the development, morphology, and survival of Pithecopus gonzagai, an anuran species endemic to the Caatinga, a tropical semiarid biome in northeastern Brazil. Tadpoles were reared under three temperature regimes: control (28.6 ± 0.7 °C), intermediate (30.8 ± 0.7 °C), and high (33.0 ± 0.9 °C), simulating present and projected future climatic conditions. Thermal acclimation significantly affected survival and metamorphic success, with the highest mortality observed at 33 °C, where no individuals completed metamorphosis. Morphological effects were transient with no clear pattern and there was no change on time to metamorphosis. Behavioral parameters, including swimming speed, mobility rate, and exploration rate, were not affected by temperature. Our findings highlight the sensitivity of early developmental stages of tropical amphibians to increased temperatures and emphasize the potential threats posed by climate change to species inhabiting already thermally challenging environments such as the Caatinga.