Behavior, Ecology, Evolution and Systematics Program, University of Maryland, College Park, Maryland 20742, USA.
Ecology. 2010 Jan;91(1):155-65. doi: 10.1890/08-2115.1.
Pollen limitation of female fecundity is widespread among angiosperms, a signal that pollinators frequently fail to transfer pollen to fertilize all ovules. Recent surveys have suggested that pollen limitation is associated with floral specialization. This study uses a group of Antillean Gesneriaceae with contrasting pollination systems (bat, hummingbird, and generalist) to assess the premise that plants with specialized pollination systems and infrequent pollinator visitation experience greater pollen limitation of fruit and seed set than their generalist congeners. Alternatively, specialists may possess mechanisms that reduce pollen limitation, such as autonomous self-pollination. A survey of autonomous self-pollination conducted on 13 Gesneria and Rhytidophyllum species during 2006-2008 revealed no significant association between reproductive assurance mechanisms and pollination system specialization. However, high levels of potential autonomous self-pollination were only found among specialized hummingbird-pollinated species. A comparison of fruit and seed set between emasculated and unmanipulated flowers provided evidence for autonomous selfing acting as a reproductive assurance mechanism in three out of four ornithophilous species. Furthermore, the Puerto Rican population of G. reticulata relies almost exclusively on self-pollination for reproduction. Two-year pollen supplementation experiments conducted on nine Gesnerieae species from the Dominican Republic and Puerto Rico provided evidence for significant pollen limitation associated with pollination specialization including both bat- and hummingbird-pollinated Gesnerieae; no pollen limitation was detected in any of the four generalist species. No pollen limitation was detected either in two ornithophilous Gesneria species with low hummingbird visitation and high levels of autonomous self-pollination. This study provides support for the idea that generalized pollination systems may, in some cases, buffer against fluctuations in the pollinator environment. However, the use of reproductive assurance mechanisms allows the maintenance of highly specialized pollination systems in pollinator depauperate environments.
花粉对雌性生殖力的限制在被子植物中普遍存在，这表明传粉者经常无法传递花粉来使所有胚珠受精。最近的调查表明，花粉限制与花部特化有关。本研究使用一组具有不同传粉系统（蝙蝠、蜂鸟和广食性）的安的列斯 Gesneriaceae 来评估以下前提：具有特化传粉系统和传粉者访问频率较低的植物比它们的广食性近缘种经历更大的花粉限制，从而导致果实和种子的形成。或者，特化种可能具有减少花粉限制的机制，例如自主自交。2006-2008 年对 13 种 Gesneria 和 Rhytidophyllum 进行的自主自交调查显示，生殖保障机制与传粉系统特化之间没有显著关联。然而，在特化的蜂鸟传粉物种中仅发现高水平的潜在自主自交。对 4 种食虫植物中未授粉花和未处理花的结实和种子形成进行比较，为自主自交作为生殖保障机制在 3 种传粉动物中发挥作用提供了证据。此外，波多黎各的 G. reticulata 种群几乎完全依赖自交进行繁殖。在多米尼加共和国和波多黎各的 9 种 Gesnerieae 物种上进行的为期两年的花粉补充实验提供了证据，表明授粉特化与花粉限制有关，包括蝙蝠和蜂鸟传粉的 Gesnerieae；在 4 种广食性物种中均未检测到花粉限制。在 2 种食虫植物中也未检测到花粉限制，这 2 种植物的蜂鸟访问量低，但自主自交水平高。本研究支持以下观点，即广义的传粉系统在某些情况下可能缓冲传粉者环境的波动。然而，生殖保障机制的使用允许在传粉者稀少的环境中维持高度特化的传粉系统。
