Variability in nectar production and standing crop, and their relation to pollinator visits in a Mediterranean shrub |
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Authors: | Tamar Keasar Adi Sadeh Avi Shmida |
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Institution: | (1) Department of Life Sciences, Achva College, Mobile Post, Shikmim, 79800, Israel;(2) Department of Biology, University of Haifa – Oranim, Tivon, 36006, Israel;(3) Department of Entomology, Agricultural Research Organization, P.O. Box 6, Bet Dagan, 50250, Israel;(4) Department of Evolution, Systematics & Ecology, The Hebrew University, Jerusalem, 91904, Israel;(5) Center for Rationality, The Hebrew University, Jerusalem, 91904, Israel |
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Abstract: | Nectar standing crops in flowers within an individual plant are often highly variable. This variability may be a by-product
of the foraging activity of insect pollinators. Alternatively, plants may be selected to produce highly variable rewards to
reduce consecutive visitation by risk-averse pollinators, thus diminishing within-plant pollen transfer. This study evaluated
the roles of pollinator control vs. plant control over nectar variability in the bee-pollinated shrub Rosmarinus officinalis L. (Lamiaceae). We sampled nectar production, standing crop and pollinator visits in three shrubs of one population over
17 days during one blooming season. Nectar production rates were highly variable (CV = 1.48), and increased after rainy days.
Nectar standing crops were even more variable (CV = 2.16), decreased with increasing temperatures, and increased with time
since the last rain. Pollinator visit rates decreased with variability in nectar standing crops, increased with flower number
per shrub, and were unaffected by variability in nectar production rates. Repeated sampling of marked flowers revealed no
correlation between their nectar standing crops and production rates. These findings support the role of reward variance in
reducing pollinator visits, but suggest that plants are not in complete control of this variability. Rather, plant-generated
variability can be modified by intensive foraging activity of pollinators. Such pollinator control over nectar variability
is likely to reduce the selective advantage of plant-generated reward variation.
Handling Editor: Neal Williams. |
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Keywords: | Geitonogamy Honeybee Rosmarinus officinalis Nectar variability Pollination |
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