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Pollination Efficiency and the Evolution of Specialized Deceptive Pollination Systems

1. Department of Structural and Functional Biology, University of Naples Federico II, complesso Universitario MSA, Via Cinthia, I‐80126 Naples, Italy;2. School of Biological and Conservation Sciences, University of KwaZulu‐Natal, P. Bag X01, Scottsville, Pietermaritzburg 3209, South Africa;3. Institute of Systematic Botany, University of Zürich, Zollikerstrasse 107, CH‐8008 Zürich, Switzerland

The ultimate causes of evolution of highly specialized pollination systems are little understood. We investigated the relationship between specialization and pollination efficiency, defined as the proportion of pollinated flowers relative to those that experienced pollen removal, using orchids with different pollination strategies as a model system. Rewarding orchids showed the highest pollination efficiency. Sexually deceptive orchids had comparably high pollination efficiency, but food‐deceptive orchids had significantly lower efficiency. Values for pollinator sharing (a measure of the degree of generalization in pollination systems) showed the reverse pattern, in that groups with high pollination efficiency had low values of pollinator sharing. Low pollinator sharing may thus be the basis for efficient pollination. Population genetic data indicated that both food‐ and sexually deceptive species have higher degrees of among‐population gene flow than do rewarding orchids. Thus, the shift from food to sexual deception may be driven by selection for more efficient pollination, without compromising the high levels of gene flow that are characteristic of deceptive species.