The adaptive accuracy of flowers: measurement and microevolutionary patterns
The adaptive accuracy of flowers: measurement and microevolutionary patterns
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DOI：
10.1093/aob/mcp095
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发表时间：
2009-06-01
期刊：
影响因子：
4.2
通讯作者：
Maad, Johanne
中科院分区：
文献类型：
--
作者：
Armbruster, W. Scott;Hansen, Thomas F.;Maad, Johanne
自达尔文时代以来，生物学家一直认为适应是向最佳性状值进化的过程，但他们通常没有评估偏离最佳性状的不同原因的相对重要性。本文以花授粉为自适应系统，通过测量自适应不精确度(表型偏差)来研究这个问题。自适应精确度至少有三个不同的组成部分，其中两个是最优性(平均值与最优值的偏差)和精确度(性状方差)。然后，我们描述了个体和群体的自适应精度。个体不准确包括基因类型目标(在一系列环境中生长的一个基因的平均表型)与最优的偏差以及围绕该基因类型目标的表型变异(表型不精确)。群体不精确度有三个基本组成部分：群体平均值与最优值的偏差、基因目标的差异和表型不精确度。此外，还提出了第四个分量，即最优值的种群内变异。这些组成部分是直接可评估的，具有相加关系，并允许探索个人和群体适应性不准确的原因。对花样本的适应性准确性进行了估计，将控制授粉者花粉沉积的花表型与适应性最佳相关联，适应性最佳被定义为最有可能将花粉带到柱头上的位置(雄性不准确)。雌性不准确的定义是柱头接触的位置与传粉者的花粉预期位置的偏差。在相似物种内部和之间的估计精度方面发现了惊人的差异。其中一些变异是由花期(花的接受期)柱头或花药位置的发育变化引起的，这可能会导致精确度估计的巨大变化。似乎有更高的精确度和精确度的趋势，在具有更高水平的整合和二性配子(性功能的时间分离)的花中，以及那些在花粉转移期间传粉者不活动(或固定)的花中。观察到较大的偏离假定的自适应最优值，这可能与冲突的选择压力对花的影响有关，例如反对自花授粉的选择促进了异花授粉(花粉和柱头的空间分离)。自适应精确度是一个有用的概念，可以用来理解种群和物种内和种内的表型平均值和花形态变异的适应意义。估计和比较适应精度的各个组成部分对于确定不准确的原因特别有帮助，例如相互冲突的选择压力、低环境渠化和发育不稳定。
From Darwin's time onward, biologists have thought about adaptation as evolution toward optimal trait values, but they have not usually assessed the relative importance of the distinct causes of deviations from optima. This problem is investigated here by measuring adaptive inaccuracy (phenotypic deviation from the optimum), using flower pollination as an adaptive system.Adaptive accuracy is shown to have at least three distinct components, two of which are optimality (deviation of the mean from the optimum) and precision (trait variance). We then describe adaptive accuracy of both individuals and populations. Individual inaccuracy comprises the deviation of the genotypic target (the mean phenotype of a genotype grown in a range of environments) from the optimum and the phenotypic variation around that genotypic target (phenotypic imprecision). Population inaccuracy has three basic components: deviation of the population mean from the optimum, variance in the genotypic targets and phenotypic imprecision. In addition, a fourth component is proposed, namely within-population variation in the optimum. These components are directly estimable, have additive relationships, and allow exploration of the causes of adaptive inaccuracy of both individuals and populations. Adaptive accuracy of a sample of flowers is estimated, relating floral phenotypes controlling pollen deposition on pollinators to adaptive optima defined as the site most likely to get pollen onto stigmas (male inaccuracy). Female inaccuracy is defined as the deviation of the position of stigma contact from the expected location of pollen on pollinators.A surprising amount of variation in estimated accuracy within and among similar species is found. Some of this variation is generated by developmental changes in positions of stigmas or anthers during anthesis (the floral receptive period), which can cause dramatic change in accuracy estimates. There seem to be trends for higher precision and accuracy in flowers with higher levels of integration and dichogamy (temporal separation of sexual functions), and in those that have pollinators that are immobile (or immobilized) during pollen transfer. Large deviations from putative adaptive optima were observed, and these may be related to the effects of conflicting selective pressures on flowers, such as selection against self-pollination promoting herkogamy (spatial separation of pollen and stigmas).Adaptive accuracy is a useful concept for understanding the adaptive significance of phenotypic means and variances of floral morphology within and among populations and species. Estimating and comparing the various components of adaptive accuracy can be particularly helpful for identifying the causes of inaccuracy, such as conflicting selective pressures, low environmental canalization and developmental instability.