Deploying seed mixes following disturbances is a common strategy used to restore bee communities. However, known spatial variation of environmental conditions and bee community composition limits the effectiveness of some plants for bee habitat restoration across a wide range of habitat types. Consequently, assemblages of plants that provide consistent resources for spatially variable bee communities will result in broadly applicable seed mixes for effective pollinator restoration on wildlands. Furthermore, seed mixes typically incorporate hearty plant species with a range of floral morphologies, colors, and phenophases to supply foraging resources to diverse bee species during the entire growing season. However, selection of species for seed mixes rarely considers the functional roles of plants in bee-plant interaction networks, and predominantly benefit common, generalist bees within communities. Consequently, plants supporting rare or unique bee assemblages that also occupy core positions in bee-plant interaction networks are high priorities for inclusion in seed mixes. We compared 12 commercially available focal-plant species for their ability to occupy keystone positions in bee-plant interaction networks and support unique bee communities relative to other plants within ponderosa pine (Pinus ponderosa) forest, subalpine lodgepole pine (Pinus contorta) forest, mid-elevation lodgepole pine forest, and riparian habitats in southwest Montana.
Results/Conclusions
While the bee community composition visiting focal-plant species was different depending on the habitat type and focal-plant species identity, the functional roles of focal-plant species in bee-plant interaction networks were consistent. Focal-plant species including Salix bebbiana (Bebb’s willow), Phacelia hastata (silverleaf scorpionweed), Rosa woodsii (Wood’s rose), and Erigeron speciosus (showy fleabane) consistently occupied the most generalist positions within bee-plant interaction networks across all habitat types. Including keystone plant species within seed mixes has the potential to support functional bee-plant interaction networks regardless of habitat type and spatially variable bee communities. However, the bee assemblages visiting focal-plant species overlapped, indicating that our selected focal-plants were redundant and the addition of other plant species in restoration seed mixes could support even more diverse bee assemblages. Our results highlight that plants in this system have reliable functional roles in bee-plant interaction networks across habitats, likely by supporting common and dominant pollinators across local communities. Future work will continue to identify plants that support rarer or more unique bee assemblages to more fully support bee community restoration.