Complete Mitogenome of Endangered and Endemic Nicobar Treeshrew (Tupaia Nicobarica) and Comparison with Other Scandentians

The Nicobar treeshrew (Tupaia nicobarica) is an endangered smaller mammal endemic to the Nicobar Island of the Andaman Sea, India regarded as an alternative experimental animal model in biomedical research. The present study aimed to assemble the first mitochondrial genome of T. nicobarica to elucidate evolutionary relationship. The structure and variation of the novel mitochondrial genome were analyzed and compared with other Scandentians. The complete mitogenome (17,164 bp) encodes 37 genes, including 13 protein-coding genes (PCGs), 22 transfer RNA (tRNAs), two ribosomal RNA (rRNAs), and one control region (CR). Most of the genes were encoded on majority strand, except nad6 and eight tRNAs. The nonsynonymous/synonymous ratio in all PCGs indicates strong negative selection among all Tupaiidae species. The comparative study of CRs revealed the occurrence of tandem repeats (CGTACA) found in T. nicobarica. The phylogenetic analyses (ML and BA) showed distinct clustering of T. nicobarica with high branch supports and depict a substantial divergence time (11.4 to 18.8 MYR) from the ancestor lineage of Tupaiidae. The 16S rRNA dataset corroborates the taxonomic rank of two subspecies of T. nicobarica from the Great and Little Nicobar Islands. The present study suggests the assembly of whole-genome to improve the understanding of evolutionary relationships of treeshrews and its implication in biomedical research.