Carr David E, Fenster Charles B, Dudash Michele R
Department of Plant Biology, University of Maryland, College Park, Maryland, 20742-5815.
Maryland Agriculture Experiment Station, University of Maryland, College Park, Maryland, 20742-5815.
Evolution. 1997 Apr;51(2):363-372. doi: 10.1111/j.1558-5646.1997.tb02423.x.
Several recent theoretical considerations of mating-system evolution predict within-population covariation between levels of inbreeding depression and genetically controlled mating-system characters. If inbreeding depression is caused by deleterious recessive alleles, families with characters that promote self-pollination should show lower levels of inbreeding depression than families with characters that promote outcrossing. The converse is expected if inbreeding depression is due to overdominant allelic interactions. Whether these associations between mating-system and viability loci evolve will have important consequences for mating-system evolution. The evolution of selfing within the genus Mimulus is associated with a reduction in stigma-anther separation (i.e., a loss of herkogamy) and high autogamous seed set. In this study we compared families from two M. guttatus populations that differed genetically in their degree of stigma-anther separation. In one of these populations we also compared families that differed genetically in the degree to which they autogamously set seed in a pollinator-free greenhouse. Dams often differed significantly in levels of inbreeding depression for aboveground biomass and flower production, but variation in inbreeding depression was never explained by herkogamy class or autogamy class. Several factors might account for why families with traits associated with selfing did not show lower inbreeding depression, and these are discussed. Our study also demonstrated significant variation among self progeny from a given female likely due to differences in pollination date and position of fruit maturation. The detection of significant dam × sire interactions suggests biparental inbreeding or differences in combining ability for specific pairs of parents.
最近关于交配系统进化的一些理论思考预测，近亲繁殖衰退水平与基因控制的交配系统特征之间存在种群内协变。如果近亲繁殖衰退是由有害隐性等位基因引起的，那么具有促进自花授粉特征的家族，其近亲繁殖衰退水平应低于具有促进异交特征的家族。如果近亲繁殖衰退是由于超显性等位基因相互作用导致的，则预期情况相反。交配系统与生存力位点之间的这些关联是否会进化，将对交配系统的进化产生重要影响。沟酸浆属内自交的进化与柱头-花药间距的减小（即雌雄异位的丧失）和高自交结实率相关。在本研究中，我们比较了来自两个沟酸浆种群的家族，这两个种群在柱头-花药间距程度上存在遗传差异。在其中一个种群中，我们还比较了在无传粉者温室中自交结实程度存在遗传差异的家族。母本在地上生物量和花产量的近亲繁殖衰退水平上往往存在显著差异，但近亲繁殖衰退的变异从未由雌雄异位类别或自交类别来解释。有几个因素可能解释了为什么具有自交相关性状的家族没有表现出较低的近亲繁殖衰退，我们对此进行了讨论。我们的研究还表明，来自给定雌株的自交后代之间存在显著变异，这可能是由于授粉日期和果实成熟位置的差异所致。显著的母本×父本相互作用的检测表明存在双亲近亲繁殖或特定亲本对的配合力差异。
