Jones Cynthia S
Department of Plant Biology, University of California, Berkeley, CA, 94720, USA.
Evolution. 1992 Dec;46(6):1827-1847. doi: 10.1111/j.1558-5646.1992.tb01172.x.
Most previous studies of evolutionary modification of form in plants have focused primarily on individual organs or flowers. Few have investigated the role of evolutionary changes in timing or position at the level of whole plant ontogeny. This study compares ontogenies of the primary shoots of two subspecies of Cucurbita argyrosperma, one a cultivar and the other its wild progenitor. Differences in flowering times between these subspecies suggested that the cultivar may have evolved from the wild subspecies via heterochronic processes leading to paedomorphosis. Analyses showed that both subspecies are similar in vegetative architecture and rates of leaf production. Earlier flowering in the cultivar, both in terms of position and absolute time, appears to have arisen through progenesis. Initial observations of leaf blade morphology led to the hypothesis that paedomorphosis and gigantism also may have been involved in the evolution of leaf blade shape in the cultivar: all leaves of the cultivar are larger and visually similar in shape to early leaves of the wild subspecies. However, quantitative analysis revealed that leaves of the cultivar are neither geometrically, nor solely allometrically larger versions of early leaves of the progenitor. Leaf shape in the cultivar exhibits novel features as well as effects of allometry shared with the progenitor, hence a simple hypothesis of paedomorphic evolution of leaf shape is not supported.
此前大多数关于植物形态进化修饰的研究主要集中在单个器官或花朵上。很少有研究在整个植物个体发育水平上探究进化变化在时间或位置上所起的作用。本研究比较了银叶南瓜两个亚种初生枝的个体发育情况，其中一个是栽培品种，另一个是其野生祖先。这两个亚种在开花时间上的差异表明，该栽培品种可能是通过导致幼态持续的异时过程从野生亚种进化而来的。分析表明，两个亚种在营养结构和叶片产生速率方面相似。栽培品种在位置和绝对时间上更早开花，似乎是通过幼期发生而出现的。对叶片形态的初步观察提出了一个假设，即幼态持续和巨型化也可能参与了栽培品种叶片形状的进化：栽培品种的所有叶片都更大，并且在视觉上与野生亚种的早期叶片形状相似。然而，定量分析表明，栽培品种的叶片既不是其祖先早期叶片的几何放大版本，也不是单纯的异速生长放大版本。栽培品种的叶片形状既表现出新颖的特征，也表现出与祖先共有的异速生长效应，因此，叶片形状幼态进化的简单假设并不成立。
