Breeding systems and pollination ecology of Uvularia grandiflora (Colchicaceae)1

Hand-pollination experiments followed by epifluorescence microscopy of pistils of Uvularia grandiflora Smith (Colchicaceae) indicated a trend toward late-acting self-incompatibility. Pollen tube growth in pistil tissue of bagged but unmanipulated flowers (mechanical self-pollination) was insignificant. As each pistil produces three stigmatic lobes, insects deposited pollen on an average of more than two in open-pollinated flowers. Medium-sized male and female bees were dominant pollen vectors representing four genera (Andrena, Lasioglossum, Nomada, and Osmia) within four families (Andrenidae, Halictidae, Apidae, and Megachilidae). Male bees comprised greater than half (59%) of the bees collected. Pollen load analysis indicates that the majority of female bees collected on U. grandiflora carried the pollen grains of the host flower's pollen mixed with grains of one or more coblooming species (polylectic foraging). The majority of nectar-drinking male bees also carried pollen loads that included grains of at least one coblooming species. We recorded pollen morphotypes of 12 coblooming vernal species on bees carrying mixed loads. Gynes of Bombus species were infrequent visitors. We report the rediscovery of females of Andrena uvulariae and the first collection of males of A. uvulariae from U. grandiflora.