Molecular Phylogenetic Assessment of Trimeresurus gunaleni Vogel, David & Sidik, 2014 (Serpentes: Viperidae: Crotalinae)

The Asian pit vipers of the genus Trimeresurus are taxonomically problematic due to extensive morphological conservatism and intraspecific variation. Trimeresurus gunaleni, a montane taxon from northern Sumatra, was described on the basis of diagnostic morphological characters and elevational segregation from lowland congeners, particularly T. sumatranus, but has lacked explicit molecular support. Here we provide new morphological observations and mitochondrial sequence data to reassess the distinctiveness and phylogenetic placement of T. gunaleni. A female specimen collected from Mount Leuser, Aceh Province, Indonesia, represents a new locality record and extends the known elevational range of the species to 2,400 m a.s.l. Its external morphology, including ventral and subcaudal counts, tail ratio, coloration, and cephalic scalation, fully agrees with the original diagnosis of T. gunaleni. We generated mitochondrial 16S rRNA and cytochrome b sequences and inferred phylogenetic relationships using partitioned maximum-likelihood analyses. The resulting tree places T. gunaleni within the subgenus Parias, although deeper relationships within the clade remain weakly resolved with mitochondrial data alone. Uncorrected p-distance values between T. gunaleni and other examined Parias species exceed commonly reported intraspecific divergences for Asian pit vipers. These data provide molecular corroboration for the species-level distinctiveness of T. gunaleni, supporting its continued recognition as a valid montane species endemic to northern Sumatra and highlighting the need for broader geographic and genomic sampling within Parias.