title: Changes in variation at the MHC class II DQA locus during the final demise of the woolly mammoth.
abstract: According to the nearly-neutral theory of evolution, the relative strengths of selection and drift shift in favour of drift at small population sizes. Numerous studies have analysed the effect of bottlenecks and small population sizes on genetic diversity in the MHC, which plays a central role in pathogen recognition and immune defense and is thus considered a model example for the study of adaptive evolution. However, to understand changes in genetic diversity at loci under selection, it is necessary to compare the genetic diversity of a population before and after the bottleneck. In this study, we analyse three fragments of the MHC DQA gene in woolly mammoth samples radiocarbon dated to before and after a well-documented bottleneck that took place about ten thousand years ago. Our results indicate a decrease in observed heterozygosity and number of alleles, suggesting that genetic drift had an impact on the variation on MHC. Based on coalescent simulations, we found no evidence of balancing selection maintaining MHC diversity during the Holocene. However, strong trans-species polymorphism among mammoths and elephants points to historical effects of balancing selection on the woolly mammoth lineage.
authors.affiliation: Department of Bioinformatics and Genetics, Swedish Museum of Natural History, SE-10405 Stockholm, Sweden.|Department of Zoology, Stockholm University, SE-10691 Stockholm, Sweden.
authors.forename: Patrícia
authors.initials: P
authors.lastname: Pečnerová
authors.affiliation: Department of Bioinformatics and Genetics, Swedish Museum of Natural History, SE-10405 Stockholm, Sweden.
authors.forename: David
authors.initials: D
authors.lastname: Díez-Del-Molino
authors.affiliation: North-East Interdisciplinary Scientific Research Institute N.A.N.A. Shilo, Far East Branch, Russian Academy of Sciences (NEISRI FEB RAS), Magadan, Russia.
authors.forename: Sergey
authors.initials: S
authors.lastname: Vartanyan
authors.affiliation: Department of Bioinformatics and Genetics, Swedish Museum of Natural History, SE-10405 Stockholm, Sweden.
authors.forename: Love
authors.initials: L
authors.lastname: Dalén
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D053476:Extinction, Biological; D005802:Genes, MHC Class II; D014644:Genetic Variation; D056665:Mammoths / Q000235:genetics*; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA