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.