Very high MHC Class IIB diversity without spatial differentiation in the Mediterranean population of Greater Flamingos

Background: 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...研究背景：病原体介导的选择压力被认为塑造了脊椎动物主要组织相容性复合体（major histocompatibility complex, MHC）基因的等位基因多样性。具体而言，针对病原体的局部适应与基因流，被认为可解释MHC等位基因多样性中观测到的大部分种内变异。然而迄今为止，证实“对当地流行病原体的适应可维持MHC多样性”的证据，仅局限于扩散能力有限、因此基因流较弱的物种。一方面，高扩散速率物种的强基因流会干扰局部适应过程；另一方面，这类物种更易遭遇病原体压力的空间异质性，这表明在泛交种群（panmictic species）的不同繁殖位点间，可能存在强烈的病原体介导选择压力。因此，在不存在……的情况下，这种跨繁殖位点的病原体介导选择压力，应当足以在高扩散物种中维持较高的MHC多样性。