Tracing Genetic Divergence and Phylogeographic Patterns of Gekko gecko Linnaeus, 1758 (Squamata: Gekkonidae) Across Southeast Asia Using RAG1 Sequence

The tokay gecko (<i>Gekko gecko</i>) is a widely distributed lizard species in Southeast Asia, with significant importance in traditional medicine and the pet trade. Previous studies using mitochondrial DNA sequences revealed extensive genetic variation across its range, indicating the presence of distinct evolutionary lineages. In this study, we assessed the nuclear genetic variation and phylogenetic pattern of <i>G. gecko</i> using the recombination activating gene 1 (<i>RAG1</i>). We analyzed 105 <i>RAG1</i> sequences from 16 localities across Thailand, Laos, and Cambodia, along with additional sequences from GenBank. Sequence analysis revealed 20 variable sites and 20 haplotypes (TgR1-TgR20). Haplotype network and phylogenetic analyses revealed strong regional structuring and at least three distinct evolutionary lineages (A-C), supported by the species delimitation test (PTP). Both red- and black-spotted morphs were present in different clades, indicating that external coloration does not correspond to genetic differentiation at this locus. Our results support the presence of distinct evolutionary lineages in <i>G. gecko</i> and emphasize the importance of integrative taxonomy for accurate species delimitation. These findings have implications for conservation, sustainable management, and regulation of international trade in this commercially exploited species.