Developmental plasticity, morphological variation and evolvability: a multilevel analysis of morphometric integration in the shape of compound leaves

The structure of compound leaves provides flexibility for morphological change by variation in the shapes, sizes and arrangement of leaflets. Here we conduct a multilevel analysis of shape variation in compound leaves to explore the developmental plasticity and evolutionary potential that are the basis of diversification in leaf shape. We use the methods of geometric morphometrics to study the shapes of individual leaflets and whole leaves in 20 taxa of Potentilla (sensu lato). A newly developed test based on the bootstrap approach suggests that uncertainty in the molecular phylogeny precludes firm conclusions whether there is a phylogenetic signal in the data on leaf shape. For variation among taxa, variation within taxa, as well as fluctuating asymmetry, there is evidence of strong morphological integration. The patterns of variation are similar across all three levels, suggesting that integration within taxa may act as a constraint on evolutionary change.

复叶的结构可通过小叶的形状、大小与排列方式的变异，为形态演化提供灵活性。本研究针对复叶的形状变异开展多层次分析，以探究作为叶片形状多样化基础的发育可塑性与演化潜力。研究采用几何形态测量学（geometric morphometrics）方法，对广义委陵菜属（Potentilla sensu lato）20个类群的单个小叶与完整复叶的形状进行分析。一项基于自举法（bootstrap）开发的全新检验显示，分子系统发育的不确定性使得我们无法就叶片形状数据中是否存在系统发育信号得出确凿结论。无论是类群间变异、类群内变异，还是波动不对称（fluctuating asymmetry）现象，均存在显著的形态整合证据。三类变异的模式高度相似，这表明类群内部的形态整合或许会对演化改变形成约束。