Floral guilds of bees in sagebrush steppe: Comparing bee usage of wildflowers available for postfire restoration

Authors: Cane, James; Love, Byron

Submitted to: Natural Areas Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/2016
Publication Date: 10/1/2016
Citation: Cane, J.H., Love, B.G. 2016. Floral guilds of bees in sagebrush steppe: Comparing bee usage of wildflowers available for postfire restoration. Natural Areas Journal. 36(4):377-391.

Interpretive Summary: Healthy plant communities of the basins and foothills of the Great Basin and adjoining regions consist of mostly wind-pollinated shrubs and grasses interspersed with a diverse mix of mostly spring-blooming perennial wildflowers. Native, non-social bees are the common floral visitors, but their floral associations and abundances are poorly known. Extrapolating from the few pollination studies, bees are the primary pollinators needed for seed production. Bees therefore will underpin success of ambitious seeding efforts to restore native forbs to impoverished plant communities following vast wildfires. This study lists and measures densities of bees visiting 17 prevalent wildflower species of the Great Basin that are, or could be, available for restoration seed mixes. More than 3800 bees representing >170 species were sampled from >35,000 plants. Species of 6 native bee genera prevailed. At the most thoroughly collected kinds of wildflowers, 70-90 native bee species were found visiting their flowers. Pollen-specialists dominated at some other wildflowers. In contrast, western yarrow and blue flax attracted the fewest bees, most of them unimportant at other wildflowers. Flax and yarrow are the two native wildflowers used most often in sagebrush-steppe seeding mixes. Success seeding more of the other wildflowers studied here would greatly improve degraded these rangelands for their diverse native bee communities.

Technical Abstract: Healthy plant communities of the American sagebrush-steppe consist of mostly wind-pollinated shrubs and grasses interspersed with a diverse mix of mostly spring-blooming, herbaceous perennial wildflowers. Native, non-social bees are the common floral visitors, but their floral associations and abundances are poorly known. Extrapolating from the few pollination studies, bees are the primary pollinators needed for seed production. Bees therefore will underpin success of ambitious seeding efforts to restore native forbs to impoverished plant communities following vast wildfires. This study quantitatively characterized the floral guilds of 17 prevalent wildflower species of the Great Basin that are, or could be, available for restoration seed mixes. More than 3800 bees representing >170 species were sampled from >35,000 plants. Species of Osmia, Andrena, Bombus, Eucera, Halictus and Lasioglossum bees prevailed. The most thoroughly collected floral guilds, at Balsamorhiza sagittata and Astragalus filipes, attracted 76 and 85 native bee species, respectively. Pollen-specialists dominated guilds at Lomatium dissectum, Penstemon speciosus and several congenerics. In contrast, the two native wildflowers used most often in sagebrush-steppe seeding mixes – A. millefolium and L. lewisii -- attracted the fewest bees, most of them unimportant in the other guilds. Success seeding more of the other wildflowers studied here would greatly improve degraded sagebrush-steppe for its diverse native bee communities.