|Nelson, Rebekah - Utah State University|
Submitted to: Journal of Melittology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/14/2015
Publication Date: 5/12/2015
Citation: Nelson, R.A., Griswold, T.L. 2015. The floral hosts and distribution of a supposed creosote bush specialist, Colletes stepheni Timberlake (Hymenoptera: Colletidae). Journal of Melittology. 49:1-12.
Interpretive Summary: Since bees are such important pollinators of crops and wildland plants, one of the most important attributes of bee species is the flowers they choose to visit. Bee species vary widely in their floral tastes. Some bees, such as honey bees and bumble bees, frequent a great diversity of flowering plants available to them. At the other extreme, some solitary bees restrict their collection of pollen to a single genus of plants. Similarly, bee species vary greatly in how wide is their range, from species that inhabit much or all of the continental United States to ones that are restricted to a single mountain range or one sand dune. The solitary bee Colletes stepheni has been considered to be one of those species with diet restricted to a single plant, creosote bush, and a very restricted distribution in the western portion of the Sonoran Desert in California. We report that this species is much more widespread, found far north into central Nevada in the Great Basin, where there is no creosote bush. There it specializes on a very different plant for pollen, indigo bush. Despite its broad distribution, it is very localized; it nests only in sand dunes. These results are a reminder that thorough studies of a species are needed in order to accurately understand the distribution and flower visiting behaviors of pollinators.
Technical Abstract: Colletes stepheni Timberlake, previously thought to be a narrow oligolege of Larrea (creosote bush) of limited distribution in the Sonoran Desert, is found to be a much more widely distributed psammophile of the Sonoran, Mojave and Great Basin Deserts that utilizes two unrelated plant pollen sources, Larrea (Zygophyllaceae) and Psorothamnus (Fabaceae). The geologic history of the region suggests a potential host shift from the more ancient occupant, Psorothamnus, to the Neogene colonizer, Larrea.