title: Very high MHC Class IIB diversity without spatial differentiation in the mediterranean population of greater Flamingos.
abstract: Selective pressure from pathogens is thought to shape the allelic diversity of major histocompatibility complex (MHC) genes in vertebrates. In particular, both local adaptation to pathogens and gene flow are thought to explain a large part of the intraspecific variation observed in MHC allelic diversity. To date, however, evidence that adaptation to locally prevalent pathogens maintains MHC variation is limited to species with limited dispersal and, hence, reduced gene flow. On the one hand high gene flow can disrupt local adaptation in species with high dispersal rates, on the other hand such species are much more likely to experience spatial variation in pathogen pressure, suggesting that there may be intense pathogen mediated selection pressure operating across breeding sites in panmictic species. Such pathogen mediated selection pressure operating across breeding sites should therefore be sufficient to maintain high MHC diversity in high dispersing species in the absence of local adaptation mechanisms. We used the Greater Flamingo, Phoenicopterus roseus, a long-lived colonial bird showing a homogeneous genetic structure of neutral markers at the scale of the Mediterranean region, to test the prediction that higher MHC allelic diversity with no population structure should occur in large panmictic populations of long-distance dispersing birds than in other resident species.
  
  
  
  We assessed the level of allelic diversity at the MHC Class IIB exon 2 from 116 individuals born in four different breeding colonies of Greater Flamingo in the Mediterranean region. We found one of the highest allelic diversity (109 alleles, 2 loci) of any non-passerine avian species investigated so far relative to the number of individuals and loci genotyped. There was no evidence of population structure between the four major Mediterranean breeding colonies.
  
  
  
  Our results suggest that local adaptation at MHC Class IIB in Greater Flamingos is constrained by high gene flow and high MHC diversity appears to be maintained by population wide pathogen-mediated selection rather than local pathogen-mediated selection. Further understanding of how pathogens vary across space and time will be crucial to further elucidate the mechanisms maintaining MHC diversity in species with large panmictic populations and high dispersal rates.
authors.affiliation: University of Ulm, Institute of Evolutionary Ecology and Conservation Genomics, Albert-Einstein Allee 11, D-89069, Ulm, Germany. Mark.Gillingham@uni-ulm.de.|Université de Bourgogne, Equipe Ecologie Evolutive, UMR CNRS 6282 Biogéosciences, 6 bd. Gabriel, 21000, Dijon, France. Mark.Gillingham@uni-ulm.de.|Centre de Recherche de la Tour du Valat, Le Sambuc, 13200, Arles, France. Mark.Gillingham@uni-ulm.de.|Leibniz Institute for Zoo and Wildlife Research, Evolutionary Genetics, Alfred-Kowalke-Str. 17, D-10315, Berlin, Germany. Mark.Gillingham@uni-ulm.de.
authors.forename: Mark A F
authors.initials: MA
authors.lastname: Gillingham
authors.affiliation: Centre de Recherche de la Tour du Valat, Le Sambuc, 13200, Arles, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Béchet
authors.affiliation: Leibniz Institute for Zoo and Wildlife Research, Evolutionary Genetics, Alfred-Kowalke-Str. 17, D-10315, Berlin, Germany.|Berlin Center for Genomics in Biodiversity Research (BeGenDiv), D-14195, Berlin, Germany.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Courtiol
authors.affiliation: R.N. Laguna de Fuente de Piedra, Consejería de Medio Ambiente y Ordenación del Territorio, Junta de Andalucía, Apartado 1, E-29520 Fuente de Piedra, (Málaga), Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Rendón-Martos
authors.affiliation: Department of Wetland Ecology, Estación Biológica de Doñana, (EBD-CSIC), calle Américo Vespucio s/n, E-41092, Sevilla, Spain.
authors.forename: Juan A
authors.initials: JA
authors.lastname: Amat
authors.affiliation: Center of Excellence for Research in Biodiversity, King Saud University, Riyadh, Saudi Arabia.|Laboratoire de recherche et de conservation des zones humides, University of Guelma, Guelma, Algeria.
authors.forename: Boudjéma
authors.initials: B
authors.lastname: Samraoui
authors.affiliation: Natural History Museum, Faculty of Sciences, Department of Biology, Ege University, Bornova, İzmir, Turkey.
authors.forename: Ortaç
authors.initials: O
authors.lastname: Onmuş
authors.affiliation: University of Ulm, Institute of Evolutionary Ecology and Conservation Genomics, Albert-Einstein Allee 11, D-89069, Ulm, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Sommer
authors.affiliation: Université de Bourgogne, Equipe Ecologie Evolutive, UMR CNRS 6282 Biogéosciences, 6 bd. Gabriel, 21000, Dijon, France.|Institut Universitaire de France, Paris, France.
authors.forename: Frank
authors.initials: F
authors.lastname: Cézilly
mesh_terms: D000483:Alleles; D000818:Animals; D001717:Birds / Q000235:genetics*; D005091:Exons; D051456:Gene Flow; D005802:Genes, MHC Class II; D014644:Genetic Variation; D005838:Genotype; D000949:Histocompatibility Antigens Class II / Q000235:genetics*; D012641:Selection, Genetic
chemical_list: D000949:Histocompatibility Antigens Class II
keywords: Allelic diversity; Greater flamingos; Local adaptation; MHC genes; Pathogen-mediated balancing selection