Genetic diversity and intraspecific mitochondrial DNA variations in the Georgian Mountain breed of Bos taurus reveal admixture, introgression and potential parallel vs. convergent evolution patterns

This study elucidates the haplotype diversity and mechanisms of evolutionary divergence for a broad population of the Georgian Mountain breed (GMB) of Bos taurus, using the sequencing and analysis of its mitochondrial DNA (mtDNA). In the evolutionary analyses, sequences of the targeted mtDNA region, involving the D-loop, CYTB, tRNA-Thr, and tRNA-Pro encoding genetic loci were analyzed using MEGA11, DnaSP, and SplitsTree software packages. A total of 25 haplotypes were determined among 82 individuals of GMB, belonging predominantly to the haplogroups T (T3, T1, T2, T4) or Q (Q1). Ten singleton haplotypes could also be determined in the GMB population. In the maximum likelihood evolutionary analysis, the singleton haplotype SNGT-9 appeared to be most closely related to the Bos indicus sub-haplogroup I1a. The haplotype diversity (0.997), nucleotide diversity (0.00636) and the overall mean distance within a population (0.01) calculated for GMB were greater as compared to the respective estimates (0.930, 0.00482 and 0.00) determined for its closest cattle relatives globally, suggesting stronger selection. It is suggested that the GMB diversity has been shaped by both parallel and convergent evolution, as well as by possible introgression, while pinpointing this breed’s ancient origin collectively.