Dorn Lisa A, Mitchell-Olds Thomas
Division of Biological Sciences, University of Montana, Missoula, MT, 59812, USA.
Evolution. 1991 Mar;45(2):371-379. doi: 10.1111/j.1558-5646.1991.tb04411.x.
Energy allocation arguments suggest a possible tradeoff between timing and magnitude of reproduction: plants that postpone reproduction may accumulate greater resources and consequently produce more offspring. However, early reproduction may be favored when adult mortality is high. Tradeoffs among life-history characters may be a consequence of constraints imposed by genetic and environmental covariation among traits. In this paper we examine the genetic basis of the relationship between timing and magnitude of reproduction in an annual plant, Brassica campestris, by selecting to change flowering date and plant size in each of four directions (early and large, late and large, early and small, or late and small). There is a strong positive relationship between flowering date and flowering height. The response to selection was greatest along the axis of positive genetic covariation. Populations may evolve to become early flowering and small or late flowering and tall, but there is little response for the alternative combinations of characters. In this instance, the constraints imposed by quantitative genetics are in striking accord with predictions that might be made on physiological, energetic, or ecological grounds.
能量分配理论表明，繁殖时间和繁殖规模之间可能存在权衡：推迟繁殖的植物可能积累更多资源，从而产生更多后代。然而，当成年个体死亡率较高时，早期繁殖可能更受青睐。生活史特征之间的权衡可能是性状间遗传和环境协变所施加限制的结果。在本文中，我们通过在四个方向（早花且植株大、晚花且植株大、早花且植株小、晚花且植株小）上进行选择，以改变一年生植物油菜的开花时间和植株大小，从而研究繁殖时间和繁殖规模之间关系的遗传基础。开花时间和开花高度之间存在很强的正相关关系。沿着正向遗传协变轴的选择反应最大。种群可能进化为早花且植株小或晚花且植株高，但对于其他性状组合几乎没有反应。在这种情况下，数量遗传学所施加的限制与基于生理、能量或生态理由所做的预测惊人地一致。
