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Ellison Abstract- 1996 Murren and Ellison

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Murren, C. J., and A. M. Ellison. 1996. Effects of habitat, plant size, and floral display on male and female reproductive success of the neotropical orchid Brassavola nodosa. Biotropica 28: 30-41.


We examined correlatively the joint effects of light, supporting plant characteristics, plant size, and floral display on pollinia removal and fruit production of 103 individuals of the orchid Brassavola nodosa (L.) Lindl. at Peter Douglas Cay, Belize, Central America. This orchid is epiphytic on red mangroves (Rhizophora mangle L. [Rhizophoraceae]), and grows from 1-300 cm above ground. Light levels above each orchid, measured as direct site factor using hemispherical canopy photography, were 6-46 percent of potential direct sunlight. To characterize plant size, we counted the number of leaves of each plant and measured its longest leaf and the leaf subtending each inflorescence. The largest orchids were found in areas of high light availability, high above ground, and on large support structures. From June through early August 1993, and again in December 1993, orchids were surveyed every 3-4 days for reproductive status and success (removal of pollinia and/or fruit production). The 48 plants that flowered during these 7 months had more and longer leaves than the 55 plants that did not flower at any time in this time period. Plants flowered continuously throughout the summer; a complete reproductive cycle (bud appearance to fruit set) lasts 2-5 weeks. Pollinia were removed from 12 percent, and fruits were set by 30 percent, of the flowers produced in the summer. Because fruit set was much lower in the fall, the total proportion of fruit production relative to flower production over the 7-month study period was only 13 percent. Path analysis indicated that direct site factor, height above ground, and diameter of supporting structures significantly contributed to plant size and floral display area. In turn, floral display significantly affected both male and female reproductive success. We conclude that resources limit flower production and components of floral display, whereas pollinator availability likely limits reproductive success in Brassavola nodosa.

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