School of Botany and Zoology, The Australian National University, Canberra, ACT 0200, Australia.
Ann Bot. 2010 May;105(5):707-17. doi: 10.1093/aob/mcq034. Epub 2010 Mar 12.
Both environmental and genetic effects contribute to phenotypic variation within and among populations. Genetic differentiation of quantitative traits among populations has been shown in many species, yet it can also be accompanied by other genetic changes, such as divergence in phenotypic plasticity and in genetic variance. Sideroxylonal (a formylated phloroglucinol compound or FPC) is an important chemical defence in eucalypts. The effect of environmental variation on its production is a critical gap in our understanding of its genetics and evolution.
The stability of genetic variation in sideroxylonal was assessed within and among populations of Eucalyptus tricarpa in three replicated provenance/progeny trials. The covariance structure of the data was also modelled to test whether genetic variances were consistent among populations and Fain's test was applied for major gene effects.
A significant genotype x environment interaction occurred at the level of population, and was related to temperature range and seasonality in source populations. Within-population genetic variation was not affected by genotype x environment effects or different sampling years. However, within-population genetic variance for sideroxylonal concentration differed significantly among source populations. Regression of family variance on family mean suggested that this trait is subject to major gene effects, which could explain the observed differences in genetic variances among populations.
These results highlight the importance of replicated common-garden experiments for understanding the genetic basis of population differences. Genotype x environment interactions are unlikely to impede evolution or responses to artificial selection on sideroxylonal, but the lack of genetic variation in some populations may be a constraint. The results are broadly consistent with localized selection on foliar defence and illustrate that differentiation in population means, whether due to selection or to drift, can be accompanied by changes in other characteristics, such as plasticity and genetic variance.
环境和遗传因素都会导致种群内和种群间的表型变异。许多物种的种群间数量性状的遗传分化已经得到证实，但也可能伴随着其他遗传变化，例如表型可塑性和遗传方差的差异。席尔酮（一种甲酰基间苯三酚化合物或 FPC）是桉树的一种重要化学防御物质。环境变化对其产生的影响是我们理解其遗传和进化的一个关键空白。
在三个重复的起源/后代试验中，评估了三脉紫胶树（Eucalyptus tricarpa）种群内和种群间席尔酮遗传变异的稳定性。还对数据的协方差结构进行了建模，以检验遗传方差是否在种群间保持一致，并应用 Fain 检验检测主基因效应。
在种群水平上发生了显著的基因型 x 环境互作，与来源种群的温度范围和季节性有关。种群内遗传变异不受基因型 x 环境效应或不同采样年份的影响。然而，席尔酮浓度的种群内遗传方差在来源种群间存在显著差异。家族方差与家族均值的回归表明，该性状受主基因效应的影响，这可以解释观察到的种群间遗传方差差异。
这些结果强调了重复的共同园林实验对于理解种群差异的遗传基础的重要性。基因型 x 环境互作不太可能阻碍对席尔酮的进化或人工选择的反应，但在一些种群中缺乏遗传变异可能是一个限制因素。这些结果与叶片防御的局部选择大致一致，并表明种群均值的分化，无论是由于选择还是漂移，都可能伴随着其他特征的变化，例如可塑性和遗传方差。
