Sweigart A L, Martin N H, Willis J H
Department of Biology, University of Rochester, Rochester, NY 14627, USA.
Mol Ecol. 2008 Apr;17(8):2089-100. doi: 10.1111/j.1365-294X.2008.03707.x. Epub 2008 Feb 28.
Here we report our characterization of a widespread, highly selfing Mimulus allotetraploid formed by interspecific hybridization between M. nasutus and M. guttatus. Nucleotide variation at two nuclear loci (mCYCA and mAP3) within and among tetraploid populations resolves two haplotype clusters for each locus: one shares near identity with sequences from M. nasutus and the other group shares substantial variation with M. guttatus. With respect to the two loci studied, each allotetraploid individual is a 'fixed heterozygote' carrying sequences from both clusters. Moreover, mCYCA variation is consistent with at least two evolutionary origins for the Mimulus allotetraploid. We show that the allotetraploid is strongly reproductively isolated from M. nasutus and M. guttatus; interploidy crosses produce almost no viable seeds. By extension, we infer strong triploid block and argue that Mimulus allotetraploid formation might proceed in one step via the union of unreduced gametes in an M. nasutus-M. guttatus F(1) hybrid. We also discuss the potential roles of mating system and flowering asynchrony in allotetraploid establishment.
在此，我们报告了对一种广泛分布、高度自交的沟酸浆属异源四倍体的特征描述，该四倍体由鼻状沟酸浆（M. nasutus）和斑点沟酸浆（M. guttatus）之间的种间杂交形成。四倍体种群内部和种群之间两个核基因座（mCYCA和mAP3）的核苷酸变异为每个基因座解析出两个单倍型簇：一个与鼻状沟酸浆的序列几乎完全相同，另一组与斑点沟酸浆有大量变异。就所研究的两个基因座而言，每个异源四倍体个体都是携带来自两个簇序列的“固定杂合子”。此外，mCYCA变异与沟酸浆属异源四倍体的至少两个进化起源一致。我们表明，该异源四倍体与鼻状沟酸浆和斑点沟酸浆在生殖上强烈隔离；倍间杂交几乎不产生 viable 种子。由此推断，存在强大的三倍体障碍，并认为沟酸浆属异源四倍体的形成可能通过鼻状沟酸浆 - 斑点沟酸浆F(1)杂种中未减数配子的结合一步完成。我们还讨论了交配系统和开花异步性在异源四倍体建立中的潜在作用。 （注：原文中“viable”未准确翻译，推测可能是“可育的”等意思，结合语境整体做了翻译调整）
