Systematics Section / ASPT
Kriebel, Ricardo , Fritsch, Peter W. , Almeda, Frank .
Discovery of gynoecial oil in flowers of Symplocos (Symplocaceae): functional and evolutionary implications.
Little is known about the reproductive biology of the amphi-Pacific, mainly tropical genus Symplocos(Symplocaceae). From observations on living plants we discovered a region of oil secretion on the style just below the receptive part of the stigma in the flowers of S. hartwegii and S. breedlovei (section Symplocastrum). To our knowledge this is the first reported case of oil production in Angiosperms by any part of the gynoecium. Before and during anthesis the anthers contact the oil, which then mixes with the pollen. Because the flowers produce abundant nectar from an epigynic ring and the pollen grains of section Symplocastrum are smooth-walled, the oil likely acts as an adhesive for pollen presentation and transport by pollinators rather than as a pollinator reward. As such the oil may also be considered an accessory pollenkitt as suggested for species in other families in which the oil is produced in the anthers. Our study of Symplocos herbarium specimens suggests that the oil-secreting ring is present in most or all of the ca. 145 species of Symplocos section Symplocastrum and absent elsewhere. By tracing floral character evolution onto the best estimate of Symplocos phylogeny based on DNA sequence data, we infer that the shift from the generalist “brush”-type floral syndrome found in most sections to the “tube”-type syndrome found in section Symplocastrum occurred in the New World via the intermediate phase represented by section Urbaniocharis, in which the stamens are arranged in a ring around the style but apparently lack an oil secretion site. This and documented visits by hummingbirds to the flowers of S. povedae of section Symplocastrum suggest that oil secretion is at least in part an adaptation to hummingbird pollination. Our discovery supports other studies that suggest a male biased function of flowers at least in some lineages.
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1 - San Francisco State University, Department of Biology, 1600 Holloway Avenue, San Francisco, California, 94132
2 - California Academy of Sciences, Department of Botany, 875 Howard Street, San Francisco, California, 94103-3009, USA
Presentation Type: Poster:Posters for Sections
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM