Term of Award

Summer 2001

Degree Name

Master of Science

Document Type and Release Option

Thesis (open access)

Department

Department of Biology

Committee Chair

Lorne M. Wolfe

Committee Member 1

Donald J. Drapalik

Committee Member 2

Alan Harvey

Committee Member 3

Lissa M. Leege

Abstract

Despite the astounding diversity of flowering plants and of mobile organisms that serve as pollinators, sympatric co-flowering plants can potentially share pollinators with each other. This places two selection pressures on plants. First, plants compete for pollinators to visit their flowers and secondly, entice pollinators to be faithful (specialized) and visit only other members of their species. I tested whether sympatric co-flowering plants reduced their selection pressures via temporal partitioning or differential attraction of pollinators using six closely related, sympatric co-flowering morning glories (Ipomoea-Convolvulaceae).

Diurnal flower phenology tightly overlapped, which did not facilitate temporal partitioning of pollinators. However, the differences in corolla color and shape allowed for predictions of differential attraction of pollinators among the six Ipomoea flowers examined based on the pollination syndrome concept. Despite the recent caveats raised about the lack of rigorous fit between floral traits and pollinator fauna over large floras, the pollination syndrome concept adequately explained pollinator preferences in Ipomoea. As predicted, bees visited bee flowers (/. hederacea, I. imperati, I. pandurata, and I. trichocnrpa), and hummingbirds and butterflies visited their respective flowers (/. hederifolia and /. quamoclit). Nectar, as predicted by the pollination syndrome concept, was of smaller volume and more concentrated in the bee flowers compared to bird flowers. Overall, bee flowers also receive much of their stigmatic pollen loads from pollen deposition by bees, whereas bird flowers received most of their stigmatic pollen loads through autogamy. Fruit and seed set were larger in bird flowers, and generally, all species had higher fruit and seed sets in 2000.

Although pollination syndromes may not adequately predict the pollinator fauna of all plants, within the Ipomoea model examined here pollination syndromes accurately explained pollinator preferences.

Copyright

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