Campbell Diane R, Waser Nickolas M
Biology Department, Gilmer Hall, University of Virginia, Charlottesville, VA, 22901.
Rocky Mountain Biological Laboratory, Crested Butte, CO, 81224.
Evolution. 1989 Nov;43(7):1444-1455. doi: 10.1111/j.1558-5646.1989.tb02595.x.
Pollen dispersal is a major component of gene flow in plant populations. It can influence microevolution within and among populations as well as the evolution of floral characters that affect dispersal. Most previous studies have relied on point estimates to characterize dispersal distances, even though there is likely to be substantial intrapopulational and interpopulational variation. We measured variation in pollen dispersal for the hummingbird-pollinated herb Ipomopsis aggregata (Polemoniaceae), using powdered fluorescent dyes to estimate pollen movement. Analysis of 5-6 natural populations in each of three years indicated that mean and mean squared distances of pollen dispersal, measured over the reproductive lifespan of individual plants, varied more than threefold among populations and years. Dispersal distances also shifted over the season within a given population. Unlike the variation among populations, these seasonal changes were associated in part with changes in flower density. The mean distance of pollen dispersal from an individual plant was unrelated to the date of first flowering, but did reflect two floral characters. Plants with higher variance in stamen length across flowers delivered pollen farther on average, as predicted by computer simulations of pollen carryover. Plants with lower mean stamen lengths also delivered pollen farther. Such effects of plant characters on pollen dispersal are a critical prerequisite for dispersal to evolve in response to its effects on fitness.
花粉传播是植物种群基因流动的一个主要组成部分。它可以影响种群内部和种群之间的微进化，以及影响传播的花部特征的进化。尽管种群内部和种群之间可能存在很大差异，但以前的大多数研究都依赖于点估计来描述传播距离。我们使用粉末状荧光染料来估计花粉移动，从而测量了由蜂鸟传粉的草本植物聚合花葱（花葱科）的花粉传播差异。对连续三年中每年的5 - 6个自然种群进行分析表明，在单个植物的整个繁殖寿命期间所测量的花粉传播平均距离和平均平方距离，在种群和年份之间变化超过三倍。在给定种群内，传播距离在季节内也会发生变化。与种群间的差异不同，这些季节性变化部分与花密度的变化有关。从单个植物传播的花粉平均距离与首次开花日期无关，但确实反映了两个花部特征。正如花粉携带的计算机模拟所预测的那样，不同花朵间雄蕊长度方差较大的植物平均传播花粉的距离更远。平均雄蕊长度较短的植物传播花粉的距离也更远。植物特征对花粉传播的这种影响是传播因对适合度的影响而进化的关键前提。
