Mitochondrial DNA variation and phylogeography of Old World camels

Abstract

Objective: Old World camels are a valuable genetic resource for many countries around the world due to their adaptation to the desert environment. They supply milk, meat and wool, and represent a major source of income to desert areas and remote communities. At present, Old World camels have encountered the challenge of unprecedented loss of genetic resources. Through our research, we would reveal the population structure and genetic variation in Old World camel populations, which provide a theoretical basis for understanding the germplasm resources and origin and evolution of different Old World camel populations..Unfortunately, the genetic diversity and phylogeography of the Old World camels are not fully documented and utilized. Methods: In the present study, we assessed mtDNA control region sequences of 182 individuals from Old World camels to unravel genetic diversity, phylogeography, and demographic dynamics. Results: Thirty-two haplotypes confirmed by 54 polymorphic sites were identified in the 156 sequences, which included 129 domestic and 27 wild Bactrian camels. Meanwhile, 14 haplotypes were defined by 47 polymorphic sites from 26 sequences in the dromedaries. The wild Bactrian camel population showed the lowest haplotype and nucleotide diversity, while the dromedaries investigated had the highest. The phylogenetic analysis suggests that there are several shared haplotypes in different Bactrian camel populations, and that there has been genetic introgression between domestic Bactrian camels and dromedaries. In addition, positive values of Tajima's D and Fu's Fs test demonstrated a decrease in population size and/or balancing selection in the wild Bactrian camel population. In contrast, the negative values of Tajima's D and Fu's Fs test in East Asian Bactrian camel populations explained the demographic expansion and/or positive selection. Conclusion: In summary, we report novel information regarding the genetic diversity, population structure and demographic dynamics of Old World camels. The findings obtained from the present study reveal that abundant genetic diversity occurs in domestic Bactrian camel populations and dromedaries, while there are low levels of haplotype and nucleotide diversity in the wild Bactrian camel population.

Review of genetic diversity in Bactrian camel (Camelus bactrianus)

“…Recently, a comprehensive study was completed to reveal genetic diversity by mtDNA control region sequences of 182 individuals from Old World camels ( Ming et al, 2021 ). Thirty-two haplotypes were confirmed in Bactrian camels, including domestic and wild two-humped camels, while 14 haplotypes were defined in dromedaries.…”

“…It can be predicted domestic Bactrian camels frequently traveled between different geographic regions. Moreover, haplotypes specific to a geographic region were also found, such as five haplotypes (H_9 to H_14) only represented in Russia Bactrian camels; H_5 and H_7 only found in Iran Bactrian camels; haplotypes H14, H17, and H18 were only discovered in Chinese Bactrian camels, and there were 12 haplotypes were only found in Mongolian Bactrian camels ( Ming et al, 2021 ).…”

“…Haplotypes of each population from different geographic regions, such as China, Mongolia, Iran, and Kazakhstan, did not cluster together according to their geographic regions. Reprinted from the Material of Ming et al (2021) .…”

Mitochondrial DNA variation of Nigerian dromedary camel (Camelus dromedarius)

“…4,8 For this reason, we used the SCIKIT-LEARN package (v0.18.0) to simulate 300 sites, and 500 offspring were generated randomly from 100 parents to further verify the accuracy of the SSR sites. 9 The detailed simulation verification method is shown in Appendix S1. The analysis results of the model deduction of different typing types and site sizes (30 times, averaging) are shown in Table S2.…”

“…[6][7][8] A recent study of the mtDNA D-loop variation in Asian camels confirms the separate position of Bactrian camels. Because we analysed a different mtDNA segment and there is hardly any overlap in the origin of the samples, we cannot link our haplotypes to those of Ming et al, 9 which would allow a comprehensive characterization of the maternal phylogeography of camel.…”