Genetic Diversity and Population Structure of Tibetan Pig Inferred from Mitochondrial DNA Sequence Analysis

Tibetan pig is an endangered plateau type pig breed which distributed mainly in Qinghai-Tibetan Plateau. In present study, researchers analyzed 218 prior published partial mitochondrial D-loop sequences (415 bp) by using phylogenetic, network, mismatch distribution and Analysis of Molecular Variance (AMOVA) analysis to clarify the population differentiation and explore the relationships among populations from different geographical locations of Tibetan pigs. The results revealed a total of 43 haplotypes in 218 samples from seven Tibetan pig populations in which only one common Haplotype (H1) was shared by the seven populations. Haplotype diversity was high (0.889) whereas nucleotide diversity among all individuals was low (0.00534). It is notable that Hezuo Tibetan pigs have 19 unique haplotypes in total 24 haplotypes of 53 individuals with the highest nucleotide diversity (0.00765). Bayesian tree and median joining network procedures carried out on the data showed that seven Tibetan pig haplotypes were essentially indistinguishable except some unique haplotypes from Hezuo. The AMOVA analysis indicated that the genetic variation mainly occurred within populations (85.41%) but variance among populations was only 14.59%. The unimodal mismatch distribution of haplotypes, together with significant negative values of Fu s FS and negative values of Tajima s D suggest that a recent population expansion of Tibetan pig has been occurred in Diqing, Hezuo and total population.