Do pollination syndromes partition the pollinator community? A test using four sympatric morning glory species

We adopted a comparative approach to evaluate whether pollination (floral) syndromes serve to partition the pollinator fauna among four coflowering species of morning glories (Ipomoea, Convolvulaceae). Two of the species (I. hederacea and I. trichocarpa) fit the bee syndrome: they produce blue and purple flowers that have large corolla openings, and they secrete smaller volumes of concentrated nectar. The other two (I. quamoclit and I. hederifolia) exhibit the bird syndrome: they have reddish flowers and narrow, tubular corollas, and they secrete larger volumes of dilute nectar. The pollinator fauna of 11 species of lepidoptera, bees, and hummingbird did not visit Ipomoea species in proportion to their relative abundance. The bumblebees foraged exclusively on the blue-flowered I. hederacea and I. trichocarpa, and the hummingbirds visited only the red-flowered I. hederifolia and I. quamoclit, while the lepidopterans exhibited less preference for a specific syndrome type. As a group, the Ipomoea species tended to be quite specialized in their use of pollinators. Ca. 75% of the visits to the blue-flowered I. hederacea and I. trichocarpa were by bumblebees, while ca. 80% of visits to I. quamoclit and I. hederifolia were by sulfur butterflies. Our results support the notion that pollination syndromes do aid in partitioning the pollinator fauna.