Armbruster W Scott, Pélabon Christophe, Hansen Thomas F, Bolstad Geir H
School of Biological Sciences, University of Portsmouth, Portsmouth PO1 2DY, UK.
Department of Biology, NTNU, N-7491, Trondheim, Norway.
New Phytol. 2009 Aug;183(3):600-617. doi: 10.1111/j.1469-8137.2009.02930.x. Epub 2009 Jul 8.
We hypothesize that pollination efficiency selects for equal distances between the pollinator reward and the anthers, and the stigmas, creating an adaptive ridge. We predict that this fitness surface governs the divergence of many plant species. We use the theory of adaptive accuracy, precision and mean optimality to assess how close populations lie to the hypothesized adaptive ridge and which factors contribute to departure from the optimum. Patterns of accuracy of pollen placement and receipt were compared across species in three study systems, Dalechampia (Euphorbiaceae), Collinsieae (Plantaginaceae) and Stylidium (Stylidiaceae), in order to assess the roles of stamen/stigma imprecision and population mean departure from the optimum in the generation of floral inaccuracy. We found that population mean departure from the optimum was the most important factor in Dalechampia, female imprecision and departure from the optimum were about equally important factors in Collinsieae, and stamen and stigma imprecision were equally important in Stylidium, with virtually no departure from the optimum. Possible reasons for imprecision and departure from the optimum were assessed using phylogenetically informed methods, indicating important roles of limited floral integration in the generation of imprecision, and conflicting selective pressures, associated with outcrossing, in the generation of departure from the optimum.
我们假设授粉效率会选择传粉者奖赏与花药以及柱头之间的等距，从而形成一个适应性脊。我们预测这种适合度曲面控制着许多植物物种的分化。我们运用适应性准确性、精确性和均值最优性理论来评估种群与假设的适应性脊的接近程度，以及哪些因素导致偏离最优状态。在三个研究系统中，即香脂属（大戟科）、柯林斯草属（车前科）和花柱草属（花柱草科），比较了不同物种间花粉放置和接收的准确性模式，以评估雄蕊/柱头不精确性以及种群均值偏离最优状态在花部不精确性产生过程中的作用。我们发现，在香脂属中，种群均值偏离最优状态是最重要的因素；在柯林斯草属中，雌蕊不精确性和偏离最优状态是同等重要的因素；在花柱草属中，雄蕊和柱头不精确性同等重要，且几乎没有偏离最优状态。我们使用系统发育信息方法评估了不精确性和偏离最优状态的可能原因，结果表明有限的花部整合在不精确性产生过程中发挥着重要作用，而与异交相关的相互冲突的选择压力在偏离最优状态的产生过程中起作用。
