An evaluation of pollination mechanisms for purple prairie-clover, Dalea purpurea (Fabaceae: Amorpheae)

Purple prairie-clover (Dalea purpurea Ventenat) is a common perennial forb that flowers during mid-summer throughout the Great Plains and adjacent biomes. Seed of D. purpurea is used for prairie restoration. This study characterizes the reproductive biology of D. purpurea. Manual pollination field trials showed that D. purpurea has a mixed pollination system. It is primarily xenogamous (45% of flowers manually pollinated with outcross pollen yielded plump seeds) but partially self-compatible (19% of selfed flowers yielded seeds). Flowers neither visited by bees nor manually pollinated rarely yielded mature seed (0-6% of flowers). A review of extensive bee community surveys from sites with prairie wildflower communities revealed that D. purpurea attracts a rich and diverse native bee fauna. Managed agricultural pollinators (Apis mellifera, Megachile rotundata) also work its flowers for pollen and nectar, yielding >20,000 seeds per plant. These observations bode well both for pollinating D. purpurea in small commercial seed fields as well as for its value for sustaining native pollinator faunas in prairie restorations.