Waser Nickolas M, Shaw Ruth G, Price Mary V
Department of Biology, University of California, Riverside, California, 92521.
Rocky Mountain Biological Laboratory, Crested Butte, Colorado, 81224.
Evolution. 1995 Feb;49(1):80-88. doi: 10.1111/j.1558-5646.1995.tb05960.x.
Events that follow pollination, such as pollen-tube growth and seed maturation, comprise an important phase of angiosperm reproduction. Differential success during this "postpollination" phase may represent phenotypic selection, including sexual selection, or interaction between parents caused, for example, by their genetic similarity. By providing a detailed partitioning of variance in success, diallel crossing designs offer great potential to determine which processes are occurring and their relative magnitudes. We performed three partial diallels with the montane herb Ipomopsis aggregata, using a large sample of parental plants (69 total). Embedded in the designs were crossing-distance treatments of 1 m, 10 m, and 100 m, reflecting a range of parental genetic similarity. We partitioned phenotypic variance in seed set per fruit into six components using restricted maximum-likelihood (REML) analysis. For one diallel, we also partitioned variance in seed mass into five components, and estimated two components of covariance between seed set and mass. Variance caused by maternal effects (V ) comprised 12%-35% of total variance in seed set and 62% of variance in seed mass, and there was a significant negative environmental covariance between seed set and seed mass. Parental interaction made no detectable contribution to phenotypic variance in either of our measures of postpollination success, although crossing distance did contribute slightly but significantly to fit of the model in some cases. Finally, there was no detectable paternal variance (V ) in seed set or seed mass. These results are in keeping with reports from other studies of natural plant populations. The finding of little or no paternal variance in particular suggests little scope for postpollination sexual selection through the male function of cosexual plants such as I. aggregata.
授粉后发生的事件，如花粉管生长和种子成熟，构成了被子植物繁殖的一个重要阶段。在这个“授粉后”阶段不同的成功率可能代表表型选择，包括性选择，或者是由亲本之间的相互作用导致的，例如它们的遗传相似性。通过详细划分成功的方差，双列杂交设计为确定哪些过程正在发生及其相对大小提供了巨大潜力。我们对山地草本植物聚合花葱进行了三次部分双列杂交，使用了大量亲本植株样本（总共69株）。在设计中嵌入了1米、10米和100米的杂交距离处理，反映了一系列亲本遗传相似性。我们使用限制最大似然法（REML）分析将每个果实的结实率的表型方差划分为六个组成部分。对于一个双列杂交，我们还将种子质量的方差划分为五个组成部分，并估计了结实率和种子质量之间的两个协方差组成部分。母本效应引起的方差（V ）占结实率总方差的12% - 35%，占种子质量方差的62%，并且结实率和种子质量之间存在显著的负环境协方差。亲本相互作用对我们任何一个授粉后成功指标的表型方差都没有可检测到的贡献，尽管在某些情况下杂交距离对模型拟合有轻微但显著的贡献。最后，在结实率或种子质量中没有可检测到的父本方差（V ）。这些结果与其他自然植物种群研究的报告一致。特别是几乎没有父本方差这一发现表明，通过聚合花葱等两性植物的雄性功能进行授粉后性选择的空间很小。
