Population characteristics of an introduced bee (Anthophora plumipes) in the N East USA and their successful use of portable adobe nesting blocks

Anthophora plumipes, a Japanese solitary bee, was imported by APHIS in 1988 as a potential pollinator of early spring crops. It is now naturalized in MD/VA/DC and continues to spread. Records from USGS’s Bee Monitoring Identification Lab (BMIL) show that it has become the predominant Anthophora species in the Washington DC region, despite a slight niche overlap with native Anthophora abrupta. To better understand A. plumipes’ biology in N America this study had two main objectives: document A. plumipes’ current range and predict future expansion based on the geologic and climatic range of the parent population in Matsue, Japan (1) and develop rearing techniques for A. plumipes and A. abrupta to allow for monitoring and competition studies in a controlled setting (2).

1. Investigate A. plumipes’ current and predicted future range: A. plumipes’ history was traced by consulting previously unreported records (perms Suzanne Batra), which include initial releases and multistate bee surveys from the 90’s.  More recent sampling data (2003 – present) came from USGS’s Bee Monitoring Inventory Lab and citizen science efforts to help locate nesting aggregations. Exact GPS coordinates were used whenever possible, which was the case for the majority of data points (x%). If exact locations were not recorded, GPS coordinates were estimated based on the information at hand. USGS geologic maps were consulted to identify regions in the USA that have substantial amounts of red clay, the substrate in which A. plumipes nest. Suitable nesting regions were matched with apt climatic conditions recorded by NOAA’s National Climatic Data Center. Results: Analyses were performed in SAS 12.1 (SAS Institute, Cary NC). A map of initial and present distributions and abundances show dramatic increases, x% and x% respectively, in the last 25 years. Predictive modelling suggests that A. plumipes will continue to rapidly increase both in range and abundance, especially in southeastern states with Georgia being the most climatically similar to their home range.

2. Developing rearing techniques for A. abrupta and A. plumipes: Adobe nesting blocks were made by mixing clay, sand, straw and water then poured into Styrofoam containers (10” x 10” x 8”). Six different compositions (clay/sand/straw ratios) were tested to find suitable nesting substrates and to determine whether optimal nesting habitat is different between species. An array of six portable adobe bee blocks, one of each composition, were randomly placed near three different nesting aggregations of each species prior to their respective emergence dates. Composition preference was measured by counting the number of capped nesting holes per block. Fitness or success rates were related to the number and size of encased juveniles observed using non-invasive X-ray techniques.  Results: A. plumipes and A. abrupta can nest successfully in a wide variety of adobe compositions, ranging from mostly clay to a more traditional cob mixture of clay heavily amended with sand and straw and did not demonstrate a clear preference for one substrate over the others. Block selection was based more on location and the lure of aggregate pheromones than on clay/sand/straw ratio.

Results from this study show that A. plumipes has expanded its range considerably in the short span of 25 years. A trend that is likely to continue as A. plumipes begins to inhabit other regions that are suitable both geologically and climatically.  Also, both native and extant anthophorine bees show a propensity for being managed in portable adobe blocks, which will prove useful for future monitoring. Understanding the basic biology of both species, as well as the drivers of their fitness will inform artificial management of these species, potentially giving farmers an alternative pollinator source for crops.