| The understanding of genetic variation in a species is very critical in the formation of its appropriate conservation strategies and protection plans. The high polymorphism of MHC genes has become a paradigm for the study of adaptive genetic variation, can consequently reflect the adaptive potential of the species.The social system of Rhinopithecus roxellana is one male unit (OMU) as the basic organizational structure of social system. But extra-unit sexual behavior often occurs in R. roxellana groups. Except the social structure, the affecting factors of animal mating system have deeper molecular mechanism. Therefore, the study of molecular mechanism of R. roxellana mate selection has important significance. MHC gene, as the optimal marker for studying species mate selection mechanism has been confirmed in multiple species.In this study, we investigated the genetic variation of MHC class ? gene DQA1, DQB1, DPB1 and DRB second exon in a small and isolated R. roxellana groups to analysis of the MHC gene polymorphism and the historical choice, for more fully information of R. roxellana adaptive genetic variation, and to provide the important reference basis to predict the potential of its adaptive evolution and conservation strategies.We also separated MHC class ? gene and individual gene typing to explore the MHC based mate choice. This has important theoretical value of understanding the formation of species mating system and provides scientific guidance for artificial breeding this endangered species.In this study, we obtained 6 alleles of DPB1 (Rhro-DPB1*01,02,03,04,05 and 06),5 alleles of DQA1 (Rhro-DQA1*01,02,03,05 and 08),5 alleles of DQB1 (Rhro-DQB1*01, 04,08,09 and 17) and 7 alleles of DRB (Rhro-DRB*02,03,05,06,08,09 and 34) from 136 samples. Among them, Rhro-DPB1*01,02,03,04,05 and 06 were found for the first time. Despite the recession the population and habitat fragmentation, DQA1 and DQB1 genes still showed high polymorphism, and DPB1 gene polymorphism remained moderate in R. roxellana. Phylogenetic analysis revealed that DPB1, DQAJ, DQB1 and DRB genes showed the characteristics of trans-species polymorphism. The selection pressure analysis revealed that DPB1 and DRB genes had a strong positive effect on the selection; DQB1 gene also had a selection pressure to some extent in the process of evolution.The analysis of the correlation of MHC class ? genes and mate choice found that there exists one of the MHC dependent mate choice hypotheses in R. roxellana groups. Alleles Rhro-DQA1*02 with the characteristics of "good genes", conformed to "choice for good genes hypothesis" of MHC mate choice. And Rhro-DQB1*17 also reflected the characteristics of "good genes" to a certain extent. There was no evidence that female mate choice conform to "choice for heterozygosity hypothesis" and "disassortative choice hypothesis" in our studied R. roxellana groups. |
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