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| Gerrhonotus occidentalis Nieto-Montes de Oca, Wiens & García-Vázquez, 2025 |
Abstract
The genus Gerrhonotus has a wide geographic range, extending from Texas in the United States southward and eastward to Panamá. Despite this enormous distribution, only seven species are currently recognized within the genus. However, both morphological and molecular studies have provided evidence for the presence of an undescribed species in western Mexico that has historically been confused with G. liocephalus. This species remains undescribed. In addition, molecular studies have revealed significant genetic structuring within some of the most broadly distributed morphology-based species in the genus, including G. infernalis, G. liocephalus, and G. ophiurus. These findings suggest the potential for unrecognized species diversity. Here, we used double-digested restriction-site associated sequencing (ddRADseq) to construct a new phylogenomic data set for the genus Gerrhonotus. We performed maximum-likelihood analyses on concatenated matrices with varying minimum taxon coverage to assess the impact of different numbers of loci and proportions of missing data on matrix informativeness, and identified the optimal matrix. We then performed a maximum-likelihood analysis of this matrix. Based on the resulting tree, current taxonomy, and the geographic distribution of samples, we identified 10 potentially independent lineages (putative species) within the genus. Subsequently, we conducted species-tree analyses for these lineages and utilized the resulting topologies to estimate their genealogical divergence index (gdi), providing a preliminary assessment of their evolutionary distinctness. All of the analyses consistently corroborated the existence of an undescribed species from western Mexico. Moreover, gdi values indicated the potential presence of additional hidden species diversity within the genus. We describe the lineage from western Mexico as a distinct species, based on 18 adult specimens. The new species appears to be restricted to the western slopes of Mexico from southern Nayarit to central Guerrero, spanning elevations from sea level to about 1500 m. Its preferred habitats include tropical deciduous, tropical semideciduous, oak, and pine-oak forests.
KEYWORDS: Alligator lizard, biodiversity, Gerrhonotus, phylogenomics, species delimitation, systematics, taxonomy
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| Gerrhonotus occidentalis in life. (A) Adult male (MZFZ 4951). (B) Adult female (MZFZ 4950). (C) Adult specimen from Colima, Cerro Alcomú n. The latter photograph was taken by J. Jones on 29 December 2023. The specimen was released. |
Gerrhonotus occidentalis sp. nov.
Adrián Nieto-Montes de Oca, John J. Wiens and Uri Omar García Vázquez. 2025. Phylogenomic Analyses Reveal Hidden Diversity in Gerrhonotus (Anguidae: Gerrhonotinae) and Description of a New Species from Western Mexico. Herpetologica. 81(3); 303-321. DOI: doi.org/10.1655/Herpetologica-D-24-00004 (5 August 2025)
