Abstract Oxygen is one of the most limiting factors in high‐altitude environments. In response to oxygen limitations, organisms can exhibit phenotypic adjustments across various levels of biological organization. Strikingly, few studies have evaluated this topic by incorporating replication across several mountain systems, which is essential for assessing the similarity of phenotypic responses across different elevation gradients. Here, we evaluated histomorphological changes in the lung and cardiac tissues in nine populations of the mesquite lizard Sceloporus grammicus , considering three elevation gradients (mountains) in the Trans‐Mexican volcanic belt. Our results show that altitude induced some histomorphological changes in the cardiorespiratory organs (lungs and cardiac ventricle), consistent with previous reports. However, we also observed that some attributes in the lung and heart tissues varied across the mountains, possibly as a result of biotic and/or abiotic factors not considered in our study. Therefore, our findings suggest that similar changes may be associated with increasing elevation in different populations of the same species, and that the particular conditions of each individual mountain may affect how those changes manifest.
Macotela et al. (2026) studied this question.