Lasioglossum bee (Halictidae) diversity in a United States Mid-Atlantic national park

Background/Question/Methods

Our study examines species identities, species flight times, and species abundances of Lasioglossum bees (Halictidae) in Dyke Marsh Wildlife Preserve (DMWP) part of a national park in Virginia, U.S.  These bees are common in many terrestrial habitats where they are dead-wood and soil aerators, nectar and pollen feeders, pollinators, and parts of food webs.  We studied the bees in a rare, tidal freshwater marsh, a flood-plain forest, and the ecotone between them.  Our analysis involves a baseline sample from 1998–1999 obtained from six Townes-style Malaise traps with two traps in each of the three habiats.  The traps were on rafts that moved up and down with tidal ebbing and flowing.  Our study addresses questions, including (1)  Which Lasioglossum species are present in DMWP?  (2)  What are the species abundances in the three focal habitats?  (3)  What are the flight times of these bees?  (4) How does the DMWP Lasioglossum diversity compare with those of other studied habitats?

Results/Conclusions

To our knowledge, this is the first quantitative bee survey that includes a freshwater, tidal marsh.  Our sample comprises 4,163 adult Lasioglossum bees of 11 species, including nine soil-nesting species, one wood-nesting species, and the rare cleptoparasitic Lasioglossum (Paralictus) michiganense.  Our Lasioglossum sample had more individuals than any other genus in our overall bee sample which is composed of five families and many other genera.  Lasioglossum bees were about three times more common in 1998 (3,113 bees) than in 1999 (1,050).  Further, the bees were more common in the ecotone and marsh than in the forest, although the soggy soil of the marsh and part of the ecotone was not appropriate for Lasioglossum soil nesting.  All three habitats had logs in which the wood-nesting L. coeruleum could nest.  Lasioglossum bees flew from April through November, showing a general spring and summer-fall peak in both years.  In this time of rapid global change, threats to DMWP include air, soil, and water pollution; many alien, invasive species; flooding; and erosion.  Lasioglossum bees, which are abundant and relatively rich in species in DMWP, are appropriate organisms for monitoring the health of DMWP in forthcoming years.