Kilkenny Francis F, Galloway Laura F
Department of Biology, University of Virginia, Charlottesville, VA 22904-4328, USA.
Oecologia. 2008 Mar;155(2):247-55. doi: 10.1007/s00442-007-0903-z. Epub 2007 Nov 16.
Plant populations often exist in spatially heterogeneous environments. Light level can directly affect plant reproductive success through resource availability or by altering pollinator behavior. It can also indirectly influence reproductive success by determining floral display size which may in turn influence pollinator attraction. We evaluated direct and indirect effects of light availability and measured phenotypic selection on phenological traits that may enhance pollen receipt in the insect-pollinated herb Campanulastrum americanum. In a natural population, plants in the sun had larger displays and received 7 times more visits than plants in the shade. Using experimental arrays to separate the direct effects of irradiance on insects from their response to display size, we found more visits to plants in the sun than in the shade, but no association between number of visits each flower received and display size. Plants in the sun were not pollen limited but pollen-augmented shade flowers produced 50% more seeds than open-pollinated flowers. Phenological traits, which may influence pollen receipt, were not under direct selection in the sun. However, earlier initiation and a longer duration of flowering were favored in the shade, which may enhance visitation in this pollen-limited habitat.
植物种群常常存在于空间异质性的环境中。光照水平可通过资源可利用性或改变传粉者行为直接影响植物的繁殖成功率。它还能通过决定花展示大小间接影响繁殖成功率，而花展示大小反过来可能影响对传粉者的吸引力。我们评估了光照可利用性的直接和间接影响，并测量了对可能增强虫媒授粉草本植物美洲风铃草花粉接受量的物候性状的表型选择。在一个自然种群中，阳光下的植物有更大的花展示，接受的访花次数比阴凉处的植物多7倍。利用实验阵列将光照对昆虫的直接影响与其对花展示大小的反应区分开来，我们发现阳光下的植物比阴凉处的植物接受的访花次数更多，但每朵花接受的访花次数与花展示大小之间没有关联。阳光下的植物不存在花粉限制，但补充花粉的阴凉处花朵比自由授粉的花朵产生的种子多50%。可能影响花粉接受量的物候性状在阳光下并未受到直接选择。然而，在阴凉处，较早开始开花和较长的花期更受青睐，这可能会增加在这个花粉限制的栖息地中的访花次数。
