Bosch Maria, Waser Nickolas M
Department of Biology, University of California, 92521, Riverside, CA, USA.
Rocky Mountain Biological Laboratory, 81224, Crested Butte, CO, USA.
Oecologia. 2001 Jan;126(1):76-83. doi: 10.1007/s004420000488. Epub 2001 Jan 1.
The density of a plant population is expected to influence reproductive success through changes in the quantity and quality of pollination service, or because both density and reproduction respond to quality of the local environment. We reported previously that seed set in sparse natural populations of Delphinium nuttallianum and Aconitum columbianum was lower than in nearby dense populations, whereas quantity of pollination service was equivalent. To explore the hypotheses that environmental quality or pollination quality are lower in sparse natural populations, leading to lower seed set, we manipulated density using arrays of potted plants. In three replicate experiments with D. nuttallianum, pollinator visitation rate and seed set were indistinguishable in sparse and dense arrays, consistent with the interpretation that environmental quality contributed to the earlier result in natural populations of this species. In three replicates with A. columbianum, visitation rate tended to increase with density, and seed set increased significantly, in contrast to our earlier result. One element of pollination quality, the degree of within-plant selfing, did not vary between sparse and dense arrays. These results highlight the complexity of mechanisms by which population parameters may influence plant reproductive success, and the temporal variation that characterizes pollination service.
植物种群密度预计会通过授粉服务数量和质量的变化影响繁殖成功率，或者是因为密度和繁殖都对当地环境质量做出反应。我们之前报道过，在纳氏翠雀花和哥伦比亚乌头稀疏的自然种群中，结实率低于附近的密集种群，而授粉服务数量相当。为了探究稀疏自然种群中环境质量或授粉质量较低导致结实率较低的假说，我们使用盆栽植物阵列来控制密度。在对纳氏翠雀花进行的三个重复实验中，稀疏和密集阵列中的传粉者访花率和结实率没有差异，这与环境质量导致该物种自然种群早期结果的解释一致。在对哥伦比亚乌头进行的三个重复实验中，访花率随密度增加而趋于上升，结实率显著增加，这与我们之前的结果相反。授粉质量的一个要素，即植物内部自交程度，在稀疏和密集阵列之间没有差异。这些结果凸显了种群参数可能影响植物繁殖成功率的机制的复杂性，以及授粉服务所具有的时间变化特征。
