POLLINATION BIOLOGY OF COLEOGYNE RAMOSISSIMA (ROSACEAE)

The pollination and breeding system of Coleogyne ramosissima (blackbru sh), a Rosaceous shrub. was examined at three locations in southern Ut ah during 1993. At each location, four branch treatments were applied: open pollination, mesh bags to prevent insect visitation, controlled cross pollination, and self pollination. Exclusion of insect pollinato rs did not affect fruit set. Mean percentage of flowers setting fruit on mesh-covered branches (48.6%) was equal to or greater than that of either open-pollinated branches (37.6%) or cross-pollinated branches ( 29.2%). Mean percent fruit set on self-pollinated branches ranged from 0.8 to 6.3%, with an overall mean of 2.7%. These data demonstrate tha t blackbrush is wind-pollinated and largely self-incompatible. Populat ional differences in overall fruit set are likely related to precious flowering and fruiting expenditures. Probable evolution of blackbrush from insect to wind pollination is discussed.