title: High MHC DQB variation and asymmetric allelic distribution in the endangered Yangtze finless porpoise, Neophocaena phocaenoides asiaeorientalis.
abstract: The endangered Yangtze finless porpoise is found in the middle and lower reaches of the Yangtze River and its adjoining big lakes. To explore the major histocompatibility complex (MHC) genetic diversity and allelic distribution patterns across its range, we investigated variation at DQB exon 2. From 76 porpoises, we identified 18 DQB sequences. The freshwater Yangtze populations had much higher allelic diversity than marine populations. Among these freshwater populations, the middle-reach population had higher allelic diversity than the lower-reach population. The high DQB diversity level, relative to that of a neutral mtDNA locus, suggests that balancing selection is acting at the DQB gene and that rapid evolution and local positive selection play critical roles in generating and retaining high MHC diversity in the freshwater population. As the balancing selection might be driven by environmental pathogens, we suggest that maintaining MHC variation should be a high priority in the conservation and management of this endangered population, especially as an ex situ conservation strategy.
authors.affiliation: Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China.
authors.forename: Hejun
authors.initials: H
authors.lastname: Du
authors.forename: Jinsong
authors.initials: J
authors.lastname: Zheng
authors.forename: Min
authors.initials: M
authors.lastname: Wu
authors.forename: Qingzhong
authors.initials: Q
authors.lastname: Zhao
authors.forename: Ding
authors.initials: D
authors.lastname: Wang
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003247:Conservation of Natural Resources; D056727:Endangered Species; D019143:Evolution, Molecular; D005091:Exons / Q000235:genetics*; D014644:Genetic Variation; D008285:Major Histocompatibility Complex / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D019576:Porpoises / Q000235:genetics*; D012641:Selection, Genetic