Thermal stress and developmental disruption in the Neotropical lizard Tropidurus torquatus under climate change scenarios

Understanding how rising temperatures influence embryonic development is essential for predicting the vulnerability of Neotropical reptiles to climate warming. This study provides the first quantitative assessment of temperature-dependent developmental anomalies in the Cerrado lizard Tropidurus torquatus . A total of 159 eggs were incubated under five thermal experimental regimes representative of natural nest temperatures under projected warming scenarios. Incubation temperature had strong, positive effects on developmental outcomes: across treatments, 35.7% of hatchlings exhibited morphological anomalies, encompassing axial, cranial, and appendicular defects. Embryonic mortality increased by ~80% in the odds per 1°C, and the probability of undesirable outcomes (mortality plus malformations) rose by ~36% in the odds per 1°C. Twelve distinct malformation types were identified, many of them severe and rarely documented in field surveys, emphasizing the importance of embryo-based assessments for revealing the true frequency of developmental abnormalities. Across all treatments, 54 malformation occurrences were recorded in 41 affected individuals, highlighting the substantial impact of thermally induced developmental disruption. Because all anomalies were observed directly in embryos or hatchlings, the recorded frequencies reflect the full expression of thermally induced disruption rather than a subset filtered by post-hatching survival. Many severe malformations occurred in embryos that failed to hatch, indicating that analyses restricted to hatchlings alone underestimate the true thermal sensitivity of developmental outcomes. These findings demonstrate that T. torquatus embryos are highly sensitive to elevated temperatures and highlight embryonic vulnerability as a critical pathway through which climate warming may reduce recruitment and ultimately compromise population persistence in Neotropical lizards.