Schierup M H, Vekemans X, Christiansen F B
Department of Ecology and Genetics, University of Aarhus, DK-8000 Aarhus C., Denmark.
Genetics. 1998 Nov;150(3):1187-98. doi: 10.1093/genetics/150.3.1187.
Expectations for the time scale and structure of allelic genealogies in finite populations are formed under three models of sporophytic self-incompatibility. The models differ in the dominance interactions among the alleles that determine the self-incompatibility phenotype: In the SSIcod model, alleles act codominantly in both pollen and style, in the SSIdom model, alleles form a dominance hierarchy, and in SSIdomcod, alleles are codominant in the style and show a dominance hierarchy in the pollen. Coalescence times of alleles rarely differ more than threefold from those under gametophytic self-incompatibility, and transspecific polymorphism is therefore expected to be equally common. The previously reported directional turnover process of alleles in the SSIdomcod model results in coalescence times lower and substitution rates higher than those in the other models. The SSIdom model assumes strong asymmetries in allelic action, and the most recessive extant allele is likely to be the most recent common ancestor. Despite these asymmetries, the expected shape of the allele genealogies does not deviate markedly from the shape of a neutral gene genealogy. The application of the results to sequence surveys of alleles, including interspecific comparisons, is discussed.
在三种孢子体自交不亲和模型下，对有限群体中等位基因谱系的时间尺度和结构形成了预期。这些模型在决定自交不亲和表型的等位基因之间的显性相互作用方面存在差异：在SSIcod模型中，等位基因在花粉和花柱中均表现为共显性；在SSIdom模型中，等位基因形成显性等级；在SSIdomcod模型中，等位基因在花柱中是共显性的，而在花粉中表现出显性等级。等位基因的合并时间与配子体自交不亲和情况下的合并时间相比，很少有超过三倍的差异，因此预计种间多态性同样常见。先前报道的SSIdomcod模型中等位基因的定向更替过程导致其合并时间比其他模型更低，替代率更高。SSIdom模型假设等位基因作用存在强烈的不对称性，现存最隐性的等位基因可能是最近的共同祖先。尽管存在这些不对称性，但等位基因谱系的预期形状与中性基因谱系的形状并没有明显偏差。本文还讨论了这些结果在等位基因序列调查（包括种间比较）中的应用。
