Quantifying the nest density of an economically important native pollinator using population genetics

Quantifying the nest density of an economically important native pollinator using population genetics

Summary

The purpose of this project is to estimate the nesting densities of an economically-important native crop pollinator as part of a broader effort to understand their value for farmers. Combining genetic approaches, geographic information systems (GIS) and field experimentation I will 1) estimate on-farm nest densities of the common eastern bumblebee (Bombus impatiens), 2) examine whether landscape pattern or management practices explain differences in nest densities between farms and 3) demonstrate how differences in pollinator community responses translate into economic benefits via changes in crop yield. Despite their ecological and economic importance, surveying bumblebee populations is challenging. Novel genetic techniques have begun to allow more rigorous estimates of nesting density. I will, for the first time, connect these techniques with economic analyses to relate nesting densities and blueberry yields in Vermont. My findings will support long-term sustainability of specialty crop agriculture by increasing growers’ ability to better manage pollinators for improved crop yield.

Objectives/Performance Targets

As outlined in the original proposal my objectives are:

• Objective 1 Use population genetics to estimate bumblebee nest density in agricultural landscapes.

• Objective 2 Identify landscape pattern and farm practices that explain differences in nest density between farms.

• Objective 3 Evaluate pollination services for a perennial berry crop.

I have made the significant progress towards completing Objective 1. This objective focuses on the question: Do perennial berry farms differ in the nest density of an important crop pollinator? To answer this question I proposed to

• Collect impatiens workers from each farm site during the 2016 summer field season.
• Extract and genotype DNA from specimens.
• Genotype extracted DNA using microsatellite markers specific to impatiens
• Use maximum-likelihood methods to assign relatedness.
• Use this relatedness score to derive a per-farm nest density estimate.

As outlined in my project timeline my intent was to complete items 1-3 by the end of January 2017. I am on track to meet this goal.

Accomplishments/Milestones

In brief, my accomplishments to date are: collection of specimens, preparation of specimens for DNA extraction, extraction of DNA from specimens.

During the 2016 Summer I collected a statistically significant number of bumblebee workers (n=120) from our study farms. With the start of the 2016 Fall semester I sought to hire a UVM undergraduate to help with DNA extractions. From October to December 2016 I employed Sami Connoly, a UVM Plant Biology student. Another student, Nawar Kareem, became interested in the project and assisted in lab work as part of his UVM work-study. From October-November we prepared over 1800 specimens for extraction. This involved arraying specimens in collection boxes to match the coordinates of sample tissues in extraction plates. This permits the unique identity and collection information of each specimen to be linked to its extracted DNA. Although this extra organizational step added time to the process of preparing specimens, this task progressed as expected and we have now extracted DNA from the majority of specimens (c. 1300). We are on track to complete this task before I travel to the Logan Bee Laboratory to perform PCR from January 16-26 2017.

            To complete the research proposed for this project I need to finish the lab work and genetic analyses outlined in Objective 1. I expect that this will be done by May 2017. I will then move on to Objective 2. This objective focuses on the questions: What are the effects of landscape composition and configuration on bumblebee nest density? How do different farm management practices influence bumblebee nest density? To answer these questions I will use already gathered GIS data to characterize the landscapes around sampled farms. I will use this information alongside the nest density data from Objective 1 to identify landscape patterns and farm practices that support larger bumblebee populations. I expect to complete Objective 2 by the end of the 2017 Summer. During the 2017 summer I will also capture video footage for the proposed outreach video. I will then move on to completing the yield analyses and economic valuation outlined in Objective 3.

Impacts and Contributions/Outcomes

This project is still in its early stages and its major contributions are forthcoming. I expect that the results from this project will connect agricultural landscapes, bumblebee populations and yield gaps in a novel and previously unreported way.

One nice surprise with this project thus far was the advising role I found myself in. In addition to completing the majority of lab work I served as a mentor to the undergraduates who worked with me. This opportunity exposed Sami and Nawar to new molecular techniques and involved them in novel, extracurricular research. While working together we would often talk about my experience as a graduate student and the steps required to get into school and secure funding. It was a pleasure to work with dedicated and inquisitive students who have both showed interests in continuing to be involved with the project on a volunteer basis. I believe that they, like me, have found sustainable agriculture research to be exciting and relevant.

Collaborators: