Muchhala Nathan
Department of Biology, University of Miami, P.O. Box 249118, FL 33124, USA.
Oecologia. 2003 Feb;134(3):373-80. doi: 10.1007/s00442-002-1132-0. Epub 2003 Jan 11.
In this study I documented the degree of specialization in the pollination systems of Burmeistera cyclostigmata and B. tenuiflora (Campanulaceae) to explore the potential role of floral isolation in the diversification of the genus. I asked which floral characteristics are important in specializing on either bat or hummingbird pollination, and whether overlap between these floral syndromes can exist. I examined nocturnal and diurnal pollen deposition, pollinator visitation rates, and single visit effectiveness and related them to intra- and interspecific variation in Burmeistera floral characteristics at Monteverde, Costa Rica. Bats and hummingbirds visited both Burmeistera species, and bats pollinated both species. Owing to differences in floral morphology, however, hummingbirds effectively pollinated only B. tenuiflora. The generalized pollination system of B. tenuiflora demonstrates that there can be overlap in the boundary between ornithophily and chiropterophily, and that nectar production and timing of anthesis do not serve as barriers between these syndromes. The high intraspecific variation in floral color from green to red or purple did not correlate with either nocturnal or diurnal pollen deposition. Degree of flower accessibility did affect pollination; nocturnal pollen deposition significantly decreased as flowers become more obstructed. In Burmeistera, floral morphology and accessibility appear to be the most important floral characteristics for specialization at the boundary between ornithophily and chiropterophily.
在本研究中，我记录了圆 stigmata 风铃草和细花风铃草（桔梗科）授粉系统的特化程度，以探究花隔离在该属多样化过程中的潜在作用。我研究了哪些花的特征对于专门由蝙蝠或蜂鸟授粉很重要，以及这些花综合征之间是否可能存在重叠。我在哥斯达黎加的蒙特维德考察了夜间和白天的花粉沉积、传粉者访花率以及单次访花的有效性，并将它们与风铃草属植物花特征的种内和种间变异联系起来。蝙蝠和蜂鸟都访了这两种风铃草，且两种风铃草都由蝙蝠授粉。然而，由于花形态的差异，蜂鸟仅有效地为细花风铃草授粉。细花风铃草的广义授粉系统表明，在鸟媒传粉和蝙蝠传粉之间的界限可能存在重叠，并且花蜜产量和开花时间并不是这些综合征之间的障碍。从绿色到红色或紫色的花颜色的高种内变异与夜间或白天的花粉沉积均无关联。花的可及程度确实影响授粉；随着花变得更难接近，夜间花粉沉积显著减少。在风铃草属中，花形态和可及程度似乎是在鸟媒传粉和蝙蝠传粉界限处特化的最重要花特征。
