Lack of floral nectar reduces self-pollination in a fly-pollinated orchid |
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Authors: | Jana Jersáková Steven D Johnson |
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Institution: | (1) School of Biological and Conservation Sciences, University of KwaZulu Natal, Private Bag X01, Pietermaritzburg, ZA, 3209, South Africa;(2) Faculty of Biological Sciences, University of South Bohemia, Branišovská 31, České Budějovice, 37005, Czech Republic;(3) Department of Theoretical Ecology, Institute of System Biology and Ecology AS CR, České Budějovice, 37005, Czech Republic |
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Abstract: | One explanation for the widespread absence of floral nectar in many orchids is that it causes pollinators to visit fewer flowers
on a plant, and thus reduces self-pollination. This, in turn, could increase fitness by reducing inbreeding depression in
progeny and promoting pollen export. The few previous investigations of this hypothesis have all involved bee-pollinated orchids
and some have given contradictory results. We studied the effects of adding artificial nectar (sucrose solution) to the spurs
of a non-rewarding long-proboscid fly-pollinated orchid, Disa pulchra. Addition of nectar significantly increased the number of flowers probed by flies (2.6-fold), the time spent on a flower
(5.4-fold), the number of pollinia removed per inflorescence (4.8-fold) and the proportion of removed pollen involved in self-pollination
(3.5-fold). The level of self-pollination increased dramatically with the number of flowers probed by flies. Experimental
self-pollination resulted in fruits with only half as many viable seeds as those arising from cross-pollination. Pollinators
were more likely to fly long distances (>40 cm) when departing from non-rewarding inflorescences than when departing from
rewarding ones. These findings provide support for the idea that floral deception serves to reduce pollinator-mediated self-pollination. |
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Keywords: | Disa pulchra Inbreeding depression Geitonogamy Plant– pollinator interaction Pollen dispersal |
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