A native ground-nesting bee (Nomia melanderi) sustainably managed to pollinate alfalfa across an intensively agricultural landscape

The world’s only intensively managed ground-nesting bee, the alkali bee (Nomia melanderi Cockerell), has been used for >50 years as an effective pollinator of alfalfa (Medicago sativa L.) grown for seed in the western USA. Across a 240 km(2) watershed in Washington, the 24 most populous of 56 nest sites found were annually surveyed for nesting bees for 8 years. Alkali bees multiplied 9-fold to 17 million females, the largest reported metapopulation of non-social bees. Several sites have remained populous for an unprecedented 50 years. The most populous nesting bed (1.5 ha) grew to 5.3 million nesting females (median = 278 nests/m(2)), the largest bee nesting aggregation ever recorded. This first-ever exhaustive landscape-level survey for any non-social bee reveals that even amid intensive conventional agriculture, a native bee can sustainably multiply to vast numbers, its nesting aggregations persisting for decades