Bumble bee nest density in diversified farms to ensure pollination services

Bumble bee nest density in diversified farms to ensure pollination services

Summary

This project aims to determine the nest density of the common eastern bumble bee, Bombus impatiens, in diversified Pennsylvanian farms. We used molecular population genetics methods to assess the number of colonies from pumpkin fields by determining the relatedness (i.e. sisterhood and kinship) of foraging worker bees collected at the farm sites. This information will allow us to estimate the number of nests in the surrounding landscape that are utilizing the crop field and are contributing to pollination.

To-date, we have collected the bee samples from 6 farm sites, and have molecularly processed all individuals (1248 total). We have begun analysis of data, and have preliminary results from one site; at least 112 colonies are represented in that sample. We have maintained pace with the timeline submitted in the original proposal, and anticipate completion of nest density from all six sites by spring 2012.

Objectives/Performance Targets

Two objectives were presented in the proposal:

Objective 1: Measure nest density by estimating how many nests are providing foragers to a specific field, from pumpkin fields in Pennsylvania.
Objective 2: Determine if colonies that are utilizing floral provisioning plots are also utilizing nearby horticultural crops.

The proposal explained that for objective 1 we would collect 150 bees from 7 pumpkin patches and we would process the bees’ genetic data and determine sisterhoods and number of colonies based on genetic relatedness. We would use similar methods for objective 2 by collecting 150 bees from 4 floral provisioning plots and compare genetic data from these bees to the genetic data of the bees from the pumpkin patches, and analyze it together to determine if the same colonies are using both the pumpkin patch and floral provisioning plot.

We were able to collect at least 200 bees from 6 pumpkin patches. We could not collect an adequate number of bumble bees from a 7th proposed site due to a high density of squash bees (another species of native bees). We were not able to collect from the 4 proposed floral provisioning plots because the floral provisioning sites did not grow as expected. At the time the proposal was written and submitted the 4 sites had been seeded, but for unknown reasons (perhaps poor establishment, management or some other unforeseen reason), the plots did not grow well. We tried to find alternative sites, but this was not logistically possible. To ameliorate this situation, we increased our sample from 150 to 200 bees at each pumpkin patch site. This will increase the robustness of our analysis by increasing sampling size and it will also allow us to test our sampling size assumptions. Further, we have tested and increased the proposed number of microsatellite markers from 7 to at least 10, which will also enhance our robustness. Upon further discussion with our collaborator, Dr. James Strange (USDA-ARS Bee Lab), we believe that these beneficial changes will allow for a more in-depth analysis, and greater confidence in the nest density estimations, and possibly lead to additional publications.

Accomplishments/Milestones

• • Collected bees from pumpkin patches at 6 different farms across a wide geographic area encompassing 4 counties in Pennsylvania o Collected: July 26-August 23, 2011 o Stored in freezer at Dept. of Entomology, Penn State campus • Shipped bees from Penn State to USDA-ARS Bee Lab in Logan, Utah o November 28, 2011 • Graduate student, Sheena Sidhu, to Logan, Utah Bee Lab to process bees and learn analysis methods o Duration of visit: December 4-17, 2011 o Completed genetic processing- 1248 bees from DNA extraction to genetic sequencing o Tested additional microsatellite markers o Learned how to use GeneMapper and Colony software programs to analyze genetic data o Analyzed one sample site completely for preliminary results

• Estimated at least 112 Bombus impatiens colonies utilizing a pumpkin patch as one field site
• Increased sampling size of bees and number of working microsatellite markers to increase robustness of project results

• Complete analysis of genetic data
o Finish by February 24, 2012
• Analyze the results to estimate nest density and compare nest density to the surrounding landscape
o March-April 2012
• Present preliminary analysis results at outreach events, extension talks, and share with growers
o Use preliminary data from the one site in 3 upcoming Extension talks:
• January 16, 2012: Sugar Valley Crops Conference, Logantown, PA
• January 24, 2012: Central Susquehanna Vegetable Grower’s Meeting, Mifflinburg, PA
• January 26, 2012: Northeast Vegetable Grower’s meeting, Clark’s Summit PA
o Use information from all six sites in additional talks beginning late February
• Complete writing for publication for submission to peer-review journal
o May 2012
• Share information about methods development and results with researchers:
o Center for Pollinator Research Symposium, May 21, 2012
o Entomological Society of America annual meeting, November 14, 2012.

Impacts and Contributions/Outcomes

There is no previous knowledge about the nest density of bumble bees (or any unmanaged native bees) in diversified farmscapes. As we proceed with this analysis, we will be able to share preliminary information that can give a sense of the number of nests in the area. This information will be shared directly with the growers from the farm sites of the collected bees, in addition to other growers, land managers and other pollinator and agroecosystem researchers. The project will result in greater impacts, contributions and outcomes once the analysis has been completed.

Collaborators: