Pollination and Plant Populations

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Science  11 Feb 2000:
Vol. 287, Issue 5455, pp. 933
DOI: 10.1126/science.287.5455.933g

The highly specialized and coevolved relationships between flowers and their pollinators—morphological, physiological, and chemical—have fascinated biologists since Darwin. Most studies have concentrated on mechanisms of the interactions and the immediate selective benefits for the plant and animal partners; in the case of the plant, the currency measured generally has been pollen transferred or fruit and seed set.

Ultimately, as Herrera points out, the pollinator regime can only be regarded as selective if it affects progeny production under natural field conditions. To investigate this question, Herrera subjected a mediterranean dwarf shrub, Lavandula latifolia, to two experimental pollinator regimes, differing in the time of day that the flowers were exposed to pollinators. Different pollinators are prevalent at different times of day. Herrera found that flowers that were exposed to pollinators during the middle of the day had a significantly better chance of producing progeny that survived for three years than flowers exposed at the beginning and end of the day. These differences were mainly the result of a higher rate of seedling emergence from the former, which in turn resulted from the higher rate of outcrossing experienced by these flowers because they were visited by a higher proportion of bee and butterfly species. Differences in pollination regimes therefore had measurable demographic consequences.—AMS

Ecology81, 15 (2000).

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