title: MHC DQB-1 polymorphism in the Gulf of California fin whale (Balaenoptera physalus) population.
abstract: One of the most isolated populations of fin whales occurs in the Gulf of California (GOC) with 400-800 individuals. This population shows reduced neutral genetic variation in comparison to the North Pacific population and thus might also display limited adaptive polymorphism. We sampled 36 fin whales from the GOC and assessed genetic variation at exon 2 of the major histocompatibility complex class II DQB-1 genes responsible for eliciting immune responses. Three divergent alleles were found with higher nonsynonymous than synonymous substitution rates within the peptide-binding region positions as well as the likely retention of ancient alleles, indicating that positive selection has shaped diversity in this species. Limited levels of nonneutral polymorphism, in addition to previously described low levels of neutral polymorphism, are consistent with the results of previous studies on vertebrate populations that have remained small and demographically stable for a very long time. Such low genetic variation in the GOC fin whales could be explained by 2 demographic scenarios: an ancient isolated population with limited gene flow or a more recent founder event after the last glacial maximum with very restricted gene flow.
authors.affiliation: Laboratorio de Ecología Molecular, Departamento de Biología Marina, Universidad Autónoma de Baja California Sur, Carretera al Sur Km. 5.5, La Paz, BCS, México 23080.
authors.forename: Sergio
authors.initials: S
authors.lastname: Nigenda-Morales
authors.forename: Sergio
authors.initials: S
authors.lastname: Flores-Ramírez
authors.forename: Jorge
authors.initials: J
authors.lastname: Urbán-R
authors.forename: Ricardo
authors.initials: R
authors.lastname: Vázquez-Juárez
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D050617:Fin Whale / Q000235:genetics*; D005802:Genes, MHC Class II; D014644:Genetic Variation; D005828:Genetics, Population; D000949:Histocompatibility Antigens Class II / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D011110:Polymorphism, Genetic
chemical_list: D000949:Histocompatibility Antigens Class II