Van Tassel David L, DeHaan Lee R, Cox Thomas S
The Land Institute Salina, KS, USA.
Evol Appl. 2010 Sep;3(5-6):434-52. doi: 10.1111/j.1752-4571.2010.00132.x. Epub 2010 May 24.
In the course of their evolution, the angiosperms have radiated into most known plant forms and life histories. Their adaptation to a recently created habitat, the crop field, produced a novel form: the plant that allocates an unprecedented 30-60% of its net productivity to sexual structures. Long-lived trees, shrubs and vines of this form evolved, as did annual herbs. Perennial herb forms with increased allocation to asexual reproduction evolved, but there are no examples of perennial herbs with high sexual effort. We suggest that sowing seed into annually tilled fields favored shorter-lived herbs because of trade-offs between first-year seed production and relative growth rate and/or persistence. By propagating cuttings, people quickly domesticated tuber crops and large woody plants. Perennial herbs were too small to be efficiently propagated by cuttings, and the association between longevity, allogamy and genetic load made rapid domestication by sexual cycles unlikely. Perennial grain crops do not exist because they could not have evolved under the original set of conditions; however, they can be deliberately developed today through artificial phenotypic and genotypic selection.
在其进化过程中，被子植物已经辐射演化成了大多数已知的植物形态和生活史。它们对最近形成的栖息地——农田的适应产生了一种新的植物形态：这种植物将其净生产力的30%至60%分配给有性结构，这一比例前所未有的高。这种形态的长寿树木、灌木和藤本植物演化了出来，一年生草本植物也是如此。增加对无性繁殖分配的多年生草本植物形态也演化了出来，但没有高有性投入的多年生草本植物的例子。我们认为，由于第一年种子生产与相对生长速率和/或持久性之间的权衡，将种子播撒到每年翻耕的田地中有利于寿命较短的草本植物。通过扦插繁殖，人们迅速驯化了块茎作物和大型木本植物。多年生草本植物太小，无法通过扦插有效地繁殖，而且寿命、异花授粉和遗传负荷之间的关联使得通过有性周期进行快速驯化不太可能。不存在多年生谷物作物，因为它们不可能在原来的条件下演化出来；然而，如今可以通过人工表型和基因型选择有意地培育它们。
