Characterization of the complete mitochondrial genome of the giant black Himalayan honeybee (Apis laboriosa) from Nepal

The giant black honeybee, Apis laboriosa, has been applied to the highlands of Southeast Asia, where the number of nests has been drastically decreasing. In this study, we first analyzed the complete mitochondrial genome of A. laboriosa from Nepal using Next sequencing technology. The mitochondrial genome is a circular molecule of approximately 1.5 kb, and includes 13 protein-coding genes (PCGs), 22 tRNA genes, two rRNA genes, and one AT-rich control region. The average AT content of the A. laboriosa mitochondrial genome is 84.7%. Start codons ATG and ATT were found in three and ten genes, respectively, while stop codons TAA and TAG were observed in 12 and 1 gene, respectively. All tRNA genes formed typical cloverleaf secondary structures, except for Ser (AGN) and Gln (Q). The heavy strand (H-strand) was predicted to have 9 PCGs and 14 tRNA genes, while the light strand (L-strand) was predicted to contain four protein-coding, eight tRNA, and two rRNA genes. The 1858 mutation sites that differ between A. laboriosa and Apis dorsata were evenly distributed throughout the mitochondrial genome. The phylogenetic relationship, inferred using 13 PCGs (based on maximum likelihood) was consistent with several previous studies that predicted a sister relationship between A. laboriosa and A. dorsata. A phylogenetic analysis inferred from the 13 mitochondrial PCGs, based on maximum likelihood, indicates that A. laboriosa and A. dorsata are very closely related. We found that the genetic distance between A. laboriosa and A. dorsata is 0.197, indicating that, while they are genetically similar enough to be considered sister species, they are indeed two distinct species.