Untangling the morphological and genetic variation of two endemic lizards from the coastal sand dunes of Northeastern Brazil

Studies in the Neotropical region consistently highlight high levels of endemism and biodiversity. However, challenges persist, particularly in uncovering the cryptic diversity among species. Various approaches are needed to address this, including morphological, genetic, and environmental data. This study focused on genetic and morphological variation in three endemic, sympatric lizard species: Tropidurus hygomi, Glaucomastix abaetensis, and Glaucomastix itabaianensis in the coastal sand dunes of Northeastern Brazil. These lizards are confined to sandy Pleistocene-formed environments with limited distribution. While earlier research revealed substantial genetic diversity, gaps remained in distribution sampling, morphological data, and understanding the correlation between this variation and environmental factors. We aimed to identify genetic clusters to assess the alignment of phenotypic differences with these clusters and explore potential relationships between climatic and geographical factors and morphometric variations. We utilized mtDNA data to assess population clusters. Geometric and linear morphometrics were employed to analyze morphological data, which was then correlated with climatic information. Results unveiled genetic and morphological variations signifying the presence of cryptic diversity. Our analyses also highlighted the influence of geography and climate on morphometric variations. These findings underscore hidden diversity and a complex evolutionary history within the confined Pleistocene sand dunes. Further genomic analyses could contribute to comprehending these patterns and enhancing the conservation strategies for these endangered species.