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1 June 2004 Nectar in Hummingbird-pollinated Neotropical Plants II: Interactions with Flower Visitors
Lucinda A. McDade, Jennifer A. Weeks
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We documented the diurnal pattern of nectar volumes in flowers of seven Neotropical hummingbird-pollinated plant species that were open to flower visitors and compared these standing crop data to nectar volumes in flowers protected from visitors. Standing crop of nectar bore little relationship to nectar in bagged flowers either in terms of volume or temporal pattern of availability. There was almost no nectar in open flowers except in those collected at dawn and those of Aphelandra sinclairiana; these were apparently too abundant to be depleted by visitors. Nectar volumes in open flowers were even more variable than in bagged flowers. We argue that understanding the evolution of plant– pollinator interactions requires understanding the relationship between nectar production and standing crop, as well as the impact of high variability on decisions by foraging animals. We conducted experiments to determine the effect of nectar removal on nectar production. Nectar removal via simulated legitimate visits had no impact on total production in flowers of Pavonia, Isertia, and Palicourea. For A. sinclairiana and Pentagonia, total nectar production in visited flowers was reduced compared to unvisited flowers. Data from individuals of these last two species indicated that the population-level pattern was assembled from individuals that responded differently to nectar removal; clearly, understanding the evolution of nectar traits demands data from individuals. We argue that detecting patterns of plant responses to nectar removal requires the context of floral characteristics (e.g., longevity, ovule number, or pollinators). Nectar removal via simulated nectar-robbing visits had no impact on total nectar production in A. sinclairiana but reduced total production in Isertia. Nectar robbing did not cause plants to invest more energy in nectar than they would have the absence of robbing. Finally, we found no difference in seed set by robbed and unrobbed flowers of A. sinclairiana. Our results add to a growing body of literature suggesting that nectar robbers are not always detrimental to plant fitness.

Lucinda A. McDade and Jennifer A. Weeks "Nectar in Hummingbird-pollinated Neotropical Plants II: Interactions with Flower Visitors," BIOTROPICA 36(2), 216-230, (1 June 2004).
Published: 1 June 2004

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Costa Rica
hummingbird pollination
nectar robbing
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