Bee associates of flowering Astragalus and Onobrychis genebank accessions at a snake river site in Eastern Washington

Abstract

A 3 yr survey of the bee associates of flowering accessions of Astragalus and Onobrychis species was conducted in open-pollinated field nurseries at Central Ferry, Washington to gain insight into the potential for bee-mediated inter-accession out-crossing in these nurseries. Such nurseries are used by genebank managers at the USDA-ARS Western Regional Plant Introduction Station (WRPIS), Pullman, Washington, to multiply seed of accessions low in viability and/or supply. Fifty-two species of bees (Hymenoptera) in the Andrenidae (4 species), Apidae (18), Colletidae (1), Halictidae (5), and Megachilidae (24) were recorded. Species-rich genera were Bombus (8 species) and Osmia (16). One undescribed species of Osmia was collected. The bee fauna was more diverse on Astragalus (45 bee species) compared to Onobrychis (29 species). Among the 24 Astragalus and 13 Onobrychis species censused, bee diversity was highest on A. bungeanus Boiss. (24 bee species), A. chaborasicus Boiss. & Hausskn. (24 species), A. miser var. serotinus (A. Gray ex J.G. Cooper) Barney (14 species), A. cicer L. (13 species), A. schistosus Boiss. & Hohen. (12 species), A. onobrychis L. (11 species), A. podolobus Boiss. & Hohen. (11 species), and Onobrychis viciifolia Scop. (10 species). The presence of a rich bee fauna in WRPIS nurseries at Central Ferry, including documented pollinators of the allogamous species A. cicer and O. viciifolia, could complicate efforts to prevent hybridization and maintain genetic integrity of genebank accessions of allogamous plant species. Our results support a 1993 decision by WRPIS curators to discontinue the practice of clustering accessions of single species of Astragalus and Onobrychis in open-pollinated nurseries to regenerate seed. © 2006 Kansas Entomological Society.