Global cytochrome c oxidase subunit I analysis reveals mitochondrial conservation in Camelus dromedarius with clear interspecific separation from other camelids.

内容摘要

The mitochondrial cytochrome c oxidase subunit I (COI) gene is widely used as a DNA barcoding marker; however, its ability to discriminate closely related camelid species and capture intraspecific variation in Camelus dromedarius remains insufficiently assessed at a global scale. In this study, we sequenced COI from 20 Algerian dromedaries and combined these data with publicly available sequences covering the same fragment, along with representative sequences from the six other extant camelid species and Bos taurus as an outgroup. Sequence alignment, diversity indices, and neutrality tests were performed using DnaSP, while genetic distances and phylogenetic relationships were inferred using Maximum Likelihood under the Tamura-Nei model. Analysis of 136 C. dromedarius COI sequences (625 bp) revealed only five polymorphic sites and four genotypes worldwide, with very low genotype diversity (Gd = 0.277), nucleotide diversity (π = 0.00145), and mean nucleotide differences (k = 0.905). The Algerian genotypes (G1 and G2) fell within this limited variation, showing ≥ 99.2% identity and minimal genetic distances (≤ 0.008) relative to reference sequences. In contrast, interspecific distances between dromedaries and other camelids were substantially higher (≈ 0.014-0.188). Phylogenetic analysis recovered well-supported clades corresponding to C. dromedarius, Bactrian camels, and New World camelids, with no overlap between intra- and interspecific variation. These findings indicate that the COI region is highly conserved within C. dromedarius but remains effective for species discrimination. The inclusion of Algerian sequences supports the low mitochondrial diversity of dromedaries and suggests a recent shared maternal ancestry across their global range.