A meager nectar offering by an epiphytic orchid is better than nothing

• Published in: Biotropica 1994-03, Vol.26 (1), p.44-49
• Main Authors: Ackerman, J.D, Rodriguez-Robles, J.A, Melendez, E.J
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; chlorostilbon maugaeus; Comparettia falcata; deception pollination; Demecology; Flowers; Fruit production; Fundamental and applied biological sciences. Psychology; Inflorescences; NECTAR; ORCHIDACEAE; Plant ecology; Plants; Plants and fungi; POLINIZACION; POLINIZADORES; Pollinating insects; POLLINATION; POLLINATORS; POLLINISATEUR; POLLINISATION; PORTO RICO; PUERTO RICO; REPRODUCCION; REPRODUCTION; Reproductive success; Trochilidae; TROPICAL ZONES; ZONA TROPICAL; ZONE TROPICALE
• ISSN: 0006-3606; 1744-7429
• DOI: 10.2307/2389109

When a nectar reward is relatively low in quality and quantity, is it an effective pollinator attractant? In Puerto Rico, Comparettia falcata, a hummingbird-pollinated epiphytic orchid, produces an average one-time secretion of 3.3-4.0 μ l of nectar (composed of 12.9-15 1% sugar) per flower. In contrast, nectar sugar concentrations of other hummingbird flowers on Caribbean islands are 17-37 percent, and those of Puerto Rico visited by the C. falcata pollinator have standing crops averaging 2.0-6.2 μ l and daily secretion rates of 3.1-10.6 μ l. In 1989 and 1990, we monitored pollinator abundance, effective flower visitation, pollinarium removals (male success), pollinations, and fruit production (female success) at two sites in the Toro Negro Forest Reserve. Reproductive success at the two sites did not differ in either year when adjusted for differences in pollinator activity In 1991, we clipped the spur tips of all flowers at one site rendering them nectarless. Visitation frequencies and measures of male and female fitness were adjusted for site differences in pollinator activity, and all were significantly lower at the site where flowers were nectarless. In 1992, we abandoned one site and manipulated the other by clipping the floral spurs of a randomly chosen subset of plants so that 25 percent of the flowers in the population were nectarless. Pollinarium removals from intact flowers were significantly different from those with cut spurs and total visits were nearly significant as well. However, the difference in female success was clearly not significant between the two treatments. The number of visits per flower dropped dramatically from previous years despite the highest level of bird activity yet censused. The data are consistent with the hypothesis that the pollinator, Chlorostilbon maugaeus. perceives the nectar reward despite its small quantity and low sugar content, this to the advantage of Comparettia flacata.