Molecular data continue to serve as an invaluable tool to assess species limits and patterns of cryptic diversity, particularly in areas harboring high levels of biodiversity. The Sceloporus scalaris group, known as bunchgrass lizards, contains 13 described and one undescribed species distributed throughout high elevation biotas of Mexico. However, recent studies suggest that diversity in the group may be substantially underestimated. We collect new sequence data from four independent loci to determine the evolutionary distinctiveness and phylogenetic relationships of an isolated population of bunchgrass lizard in the Sierra San Juan (SSJ) in the Mexican state of Nayarit. Concatenation and coalescent-based phylogenetic and species delimitation analyses suggest that this population represents a distinct evolutionary lineage allied to the S. scalaris group. We describe the new SSJ population as a new species to better account for its morphological and evolutionary distinctiveness. Divergence within the species occurred during the Neogene and Quaternary, most likely due to range shifts associated with mountain uplift and glacial-interglacial cycles. Our results provide additional evidence that supports the importance of the Mexican highlands as a biodiversity hotspot which maintains cryptic lineages awaiting discovery.

Keywords: Sceloporus scalaris group; Cryptic diversity; Mexican Transition Zone; North America; phylogenetic relationships.

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