Bos David H, Williams Rod N, Gopurenko David, Bulut Zafer, DeWoody J Andrew
Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN, USA.
Mol Ecol. 2009 Aug;18(15):3307-15. doi: 10.1111/j.1365-294X.2009.04242.x. Epub 2009 Jun 5.
Major histocompatibility complex (MHC) alleles likely have adaptive value because of overdominance, in which case MHC heterozygous individuals have increased fitness relative to homozygotes. Because of this potential benefit, the evolution of sexual reproduction between MHC-divergent individuals (i.e. negative assortative mating, NAM) may be favoured. However, the strongest evidence for MHC-based NAM comes from inbred animals, and context-dependent mating preferences have rarely been evaluated although they often occur in nature. We assessed the extent MHC-based mating preferences among wild tiger salamanders (Ambystoma tigrinum) using multiple molecular approaches. We genotyped 102 adults and 864 larvae from 36 breeding trials at both microsatellite and MHC loci. Parentage analysis revealed that reproductive success among males was positively associated with increased tail length and that with respect to the focal female, MHC-similar males sired a significantly higher number of offspring than more dissimilar males. This trend was consistent, even under context-dependent scenarios that favour traditional MHC-based NAM. These results suggest that the most MHC-divergent males may be at a reproductive disadvantage in pairwise breeding trials. Our data add to a growing body of evidence that suggests where it exists, MHC-based choice is probably dynamic and mediated by many factors that vary in the wild, notably signals from other indicator traits and by the quality and quantity of potential mates.
主要组织相容性复合体（MHC）等位基因可能具有适应性价值，因为存在超显性现象，在这种情况下，MHC杂合个体相对于纯合个体具有更高的适应性。由于这种潜在益处，MHC差异个体之间的有性繁殖进化（即负选型交配，NAM）可能会受到青睐。然而，基于MHC的NAM的最有力证据来自近交动物，尽管上下文依赖的交配偏好经常在自然界中出现，但很少被评估。我们使用多种分子方法评估了野生虎螈（Ambystoma tigrinum）中基于MHC的交配偏好程度。我们对来自36次繁殖试验的102只成年个体和864只幼体在微卫星和MHC位点进行了基因分型。亲权分析表明，雄性的繁殖成功率与尾巴长度增加呈正相关，并且对于焦点雌性而言，MHC相似的雄性比差异较大的雄性产生的后代数量显著更多。即使在有利于传统基于MHC的NAM的上下文依赖情景下，这种趋势也是一致的。这些结果表明，在成对繁殖试验中，MHC差异最大的雄性可能处于繁殖劣势。我们的数据增加了越来越多的证据，表明在存在基于MHC的选择的地方，它可能是动态的，并由许多在野外变化的因素介导，特别是来自其他指示性状的信号以及潜在配偶的质量和数量。
