Do Human-modified Landscapes Affect Solitary Bee Diversity, Foraging, and Reproduction in Northern Florida?

Do Human-modified Landscapes Affect Solitary Bee Diversity, Foraging, and Reproduction in Northern Florida?

Summary

2012 followed 2011 in methodology and data collected with a few changes. One farmer became unreachable in 2012, and one farm failed to produce crops that would attract bees. Fortunately, the 2011 data is still available. I implemented a new method for attracting bees on farms using potted, flowering plants. These mobile plants successfully attracted a couple of additional bee species for the study. Working with several undergraduate assistants, I was also able to get all bee bowl specimens pinned and labeled before the year’s end. The process of identifying bee specimens also began in 2012.

• Cover photo: View of Labeled Native Bees in Project Collection

Objectives/Performance Targets

Objectives

The objective of my study is to determine whether on farm management of vegetation is a better predictor of native bee species richness than surrounding landscape factors. The twelve farms in the study are variable in on farm vegetation management from closely mown lawn-like field verges to weedy verges and purposeful plantings of white clover and sunflowers as crops or groundcover. Do such plantings and vegetation affect the native bee diversity on these farms, or is diversity driven by landscape context? To answer this question, my study has four main objectives: 1) analysis of bee foraging habitat, 2) characterization of the landscape context of farms, 3) analysis of native bee species richness (with bee observations on potted plants added in 2012), and 4) analysis of pollen collection on farms by native bees.

Performance Targets

•Landscape Context Effects: The landscapes around the 12 farms in the study are dominated by forest (pine plantations and mixed oak woodlands) and agricultural land covers (crops and pastures). The landscape mosaic around these farms also includes developed areas (i.e., roads, parking lots, and houses) and wetlands. Last year I included a table in my report that showed preliminary estimates of dominant and secondary land covers in the immediate vicinity of the farms. In 2012 I began the process of quantifying the land cover types around each farm out to a distance of three kilometers.

• Bee Foraging Habitat: The focus of this part of my study is to quantify the foraging habitat available for bees on the twelve farms. Foraging habitat includes crops that are flowering at different sampling times, farm edge vegetation, and habitat contained on some farms like preserved wetlands. I will determine if such habitats correlate with bee diversity on the farms.

•Bee Species Richness: This part of my study focuses on bee diversity and abundance on the farms. Three kinds of sampling contribute to this data, the original two implemented in 2001 (hand netting and bee bowls) and use of flowering, potted plants to attract bees on the farm implemented in 2012.

•Bee Pollen Choices: Here my study focuses on a possible pollination precursor- what bees are carrying as they forage on farms. Native bees collect and carry pollen to store for later consumption by their offspring, but the fact that they have this pollen on their bodies increases the likelihood that they may be pollinating flowers as they move between flowers. Figuring out if they are actually pollinating flowers or their effectiveness at pollination is beyond the scope of this study.

• Figure 1. The focus of this study is the influence of landscape and on-farm vegetation on native bees.

Accomplishments/Milestones

•Landscape Context Effects: A total of twelve farms participated in this native bee study. I hired two assistants to quantify the land cover around the study’s farms. After consideration of the issue I discussed in last year’s report, I decided that land cover related more closely to bee habitat than anthropogenic land use types. So, using the Florida Natural Area Inventory’s Land Cover Map in ArcGIS my assistants tallied up the number of one hundred meter squares of each cover type within 6 five hundred meter buffers around each farm. With the help of Karl Didier, a scientist from the Wildlife Conservation Society, we automated the process in ArcGIS. The landscape data is now complete and ready for analysis.

•Bee foraging Habitat: This field work (i.e., quadrat sampling along transects, sampling around farm edges, and sampling on farm habitats) was completed in 2012. Data entry is ongoing.

•Bee Species Richness: Over 600 specimens were collected by hand and through the use of bee bowls throughout the study in 2012. I started identifying bees in 2012 and this process continues under the supervision of Dr. Glenn Hall. Additional bees species (previously not seen in the study) were collected from potted, flowering plants placed on the farms.

•Bee Pollen Choices: All of the pollen samples from native bees collected in 2011 have been processed and permanently mounted in glycerin jelly. About 30 specimens (half those collected in 2012) were processed in 2012. About 40 pollen-carrying bees remain to be identified and processed. After processing the samples, pollen identification will begin with the task of differentiating agricultural crop pollen from weedy plants. I will also assess the relative abundance of different pollen type in the samples.

• Bee assistant, Amanda Heh, is shown here keeping the plants well watered.
• Plants were brought to the farm and left for 24 hours before scan sampling for visiting bees.

Impacts and Contributions/Outcomes

In light of the decline in honeybee populations in North America there is speculation about the ability of native bees to pollinate crops, possibly replacing or at least supplementing honeybee pollination services. This project looks at two critical questions: do native bees carry crop pollen, and is it local vegetation structure around farms or broader landscape context that has more effect on native bee populations? The first question relates to native bees’ potential to pollinate crops and the second will provide basic information on whether on-farm vegetation management would be sufficient to support native bee communities. In other words, the results of this study will help farmers to know whether native bees are dependent on where their farms are located, how vegetation is managed on their farm, or some combination of the two.

Collaborators: