Cruzan Mitchell B, Neal Paul R, Willson Mary F
Department of Ecology and Evolution, Stale University of New York, Stony Brook, NY, 11794.
Department of Ecology, Ethology, and Evolution, Shelford Vivarium, University of Illinois, 606 E. Healey St., Champaign, IL, 61820.
Evolution. 1988 May;42(3):505-515. doi: 10.1111/j.1558-5646.1988.tb04156.x.
The inflorescences of Phyla incisa consist of flowers in two phases: younger, nectar-containing flowers that have yellow corolla throats and older, nectar-lacking flowers that have dark purple corolla throats. Observations of pollinator visitation patterns to both natural and manipulated inflorescences were made to determine the role of each flower phase in pollinator attraction. The effect of older-phase flowers on male and female reproductive success was determined by comparing stigmatic pollen loads and estimates of pollen removal from inflorescences having different numbers of these flowers. The pollinators of Phyla selected larger inflorescences more often than expected based upon the size distribution of inflorescences available to them. Both younger- and older-phase flowers contributed to the attraction of pollinators, but the latter were less effective in this function. The presence of older-phase flowers significantly increased the visitation rate to inflorescences and the amount of pollen removed but had little effect on pollen deposition on stigmas. The lack of correspondence between pollen deposition and pollinator-visitation rate was not due to stigma saturation, since stigma loads varied greatly. The data indicate that the deposition of pollen on stigmas in this species is a relatively stochastic process, whereas pollen removal from inflorescences occurs at a much more regular rate. Old-phase flower retention appears to contribute to reproductive success through increased pollen donation when pollinator activity is high and may also increase the probability of seed set when pollinators are rare.
较年轻的、含有花蜜的花，其花冠喉部为黄色；较老的、不含花蜜的花，其花冠喉部为深紫色。对传粉者拜访自然花序和人工花序模式进行观察，以确定每个花阶段在吸引传粉者方面的作用。通过比较不同数量的老阶段花的花序上的柱头花粉负载量和花粉去除量估计值，来确定老阶段花对雄性和雌性繁殖成功率的影响。与基于传粉者可利用的花序大小分布所预期的相比，鳞花草的传粉者更频繁地选择较大的花序。较年轻阶段和较老阶段的花都有助于吸引传粉者，但后者在这一功能上效果较差。老阶段花的存在显著提高了对花序的拜访率和花粉去除量，但对花粉在柱头上的沉积影响不大。花粉沉积与传粉者拜访率之间缺乏对应关系并非由于柱头饱和，因为柱头负载量差异很大。数据表明，该物种中花粉在柱头上的沉积是一个相对随机的过程，而从花序上去除花粉的速率则要规律得多。保留老阶段花似乎在传粉者活动频繁时通过增加花粉传播量对繁殖成功有贡献，并且在传粉者稀少时也可能增加结实的概率。
