Genomic insights into the convergent evolution of desert adaptation in camels and antelopes.

Extreme heat and chronic water scarcity present formidable challenges to large desert-dwelling mammals. In addition to camels, antelopes within the Hippotraginae and Alcelaphinae subfamilies also exhibit remarkable physiological and genetic specializations for desert survival. Among them, the critically endangered addax ( Addax nasomaculatus) represents the most desert-adapted antelope species. However, the evolutionary and molecular mechanisms underlying desert adaptations remain largely unexplored. Herein, a high-quality genome assembly of the addax was generated to investigate the molecular evolution of desert adaptation in camels and desert antelopes. Comparative genomic analyses identified 136 genes harboring convergent amino acid substitutions implicated in crucial biological processes, including water reabsorption, fat metabolism, and stress response. Notably, a convergent R146S amino acid mutation in the prostaglandin EP2 receptor gene PTGER2 significantly reduced receptor activity, potentially facilitating large-mammal adaptation to arid environments. Lineage-specific innovations were also identified in desert antelopes, including previously uncharacterized conserved non-coding elements. Functional assays revealed that several of these elements exerted significant regulatory effects in vitro, suggesting potential roles in adaptive gene expression. Additionally, signals of introgression and variation in genetic load were observed, indicating their possible influence on desert adaptation. These findings provide insights into the sequential evolutionary processes that drive physiological resilience in arid environments and highlight the importance of convergent evolution in shaping adaptive traits in large terrestrial mammals.