Genetic variation in mitochondrial genes of honey bee Apis cerana in Thailand

Abstract

PCR-RFLP of three mtDNA regions (sRNA gene, IrRNA gene and inter CO I – CO II region) and partial sequences of mitochondrial IrRNA gene were used to investigate for genetic variation and population genetic variation and population structure of honey bee Apis cerana in Thailand. Samples used for PCR-RFLP analysis included 172 colonies covering five geographic locations which were 1)North 2)North-East 3)Cental 4)South and 5)Samui Island. Three, five and eight haplotypes were obtained from Dra I digestion of PCR-amplified 400 bp sRNA gene, 750 bp IrRNA gene and 1710 bp inter CO I-CO II region, respectively. These three mtDNA regions employed in this study generated thirteen composite haplotypes. Genetic distance among populations were then calculated and used for phylogenetic reconstant using UPGMA approach. Two genetically distinctive groups : Northern (North, North-East and Central ) and Southern (South and Samui Island ) A. cerana were clearly separated. Estimated nucleotide sequence divergence between these two groups was 1.245 %. However, only haplotype C of IrRNA gene was specifically found in Samui Island. When geographic heterogeneity was analysed with a Monte Carlo Simulation, the results showed three distinctive groups where the Samui A, cerana could be further separated from the South (p=0.0000). Moreover, individuals previously analysed and showed all detected IrRNA-Dra I genotypes were sequenced after amplification. Six hundred and fifty nine nucleotides were then obtained after alignment of all sequences. An AT bias was found at 84.47% resulted in two times higher of transversions than transitions. Seventy-one mutation steps were found that contained fourteen deletions or insertions and fifty-seven point mutations. Genetic distance calculated from DNA sequence data was subjected to UPGMA approach. The sequence analysis was corrected with the results from PCR-RFLP. Notably, private haplotypes of all amplified regions were found from two samples in the South. The composite haplotypes, CED, was extremely different from all samples having morphological similarity. It was suspected to be the other species. Therefore, further study is needed to be carried out to clarify their actual taxonomic status.