|404 Life Sciences Building - LSU
Baton Rouge, LA 70803
My goal as researcher is to determine how and why human-mediated landscapes fundamentally alter arthropod communities (pollinators, natural enemies, invasive species, and threatened species) and associated ecosystem services or vulnerabilities.
1. Do management decisions in agroecosystems change insect community dynamics and ecosystem services across space and time?
2. What processes (i.e. dispersal limitations, trophic interactions, need for specific micro-climates, and physiological susceptibility to disease) are driving these shifts?
3. How can we best communicate with stakeholders to implement best management practices?
To address these questions, I am currently focusing on how trophic interactions in agricultural systems change with spatial scale, arthropod and plant community composition, as well as management tactics such as breeding and insecticide use. I also work extensively with the agricultural economics to determine both public and stakeholder knowledge of these systems and willingness to adopt more sustainable management measures.
The primary focus of my dissertation work focused on the intersection of landscape ecology and food web dynamics between natural enemies and pest species of soybeans. I was interested in how surrounding land use and fragmentation at regional and on-farm scales contributed to the abundance and diversity of natural enemies within our field sites. With help from Kentucky extension agents and local growers, I was able to sample insect communities in grower-managed fields for three years across central and western Kentucky. I was able to map the within-field spatial distributions of natural enemies and their potential prey items throughout each growing season and found significant spatial overlaps of these communities, particularly early in the season when predation might yield the greatest benefits to growers.
Evaluating the trophic interactions occurring in these areas of spatial overlap using molecular gut content analysis turned out to be a little bit more involved than I had originally anticipated. First, we (James Harwood and Eric Chapman) needed to determine if aphid honeydew contained aphid DNA that would cause natural enemies to falsely test positive for aphid DNA without actually consuming the aphid. This ended up not being a problem – of three aphid species tested, no DNA was found in the honeydew. Furthermore, I found in preliminary lab tests that ants fed a particular prey item in the lab were not testing positive for that prey item. We did a series of dissections to determine that in some ant species, the gut actually causes some inhibition of PCR. To get around this, we developed a method of exuding the crop contents and amplifying that exudate using BSA to help prevent any inhibition.
Using the newly established molecular methods for ants, I was able to work with Brian Lee and Kacie Athey to develop methods to integrate landscape-level data with our gut content data for ants in soybeans. We found that differing land uses contributed to the abundances of ant and pest communities, but that overall increased land use diversity and decreased fragmentation is correlated with an increased likelihood within-field spatial overlap of ants to pests and increased likelihood of predation events.
Due to an unfortunately high deer population near our field sites in 2017, I have been able to measure a strong gradient of browse pressure among the Miami University soybean fields. Since then, undergraduate researcher Aby VanGorder and Ph.D. candidate Michael Mahon have taken on a project with me to evaluate the impact of deer browse intensity on insect herbivore communities. We are looking at how browse density alters the levelss of insect chewing damage, pest abundance, and soybean yield responses.
As part of my current position in the LSU Public Health Lab and in collaboration with the USDA Honeybee Lab, I am investigating how commercial honeybee management decisions alter colony susceptibility to disease. As a large, multi-year study, we are following several hundred migratory hives throughout their travels from the Southeastern US to the Dakotas and ultimately to California. We are currently in the middle of the second year, where we are looking at breeding for hygienic behavior and mite treatments on colony health and pathogen incidence.
I am also evaluating five genetic stocks of honeybees for their susceptibility to Varroa mites and the deformed wing virus (DWV) those mites transmit. To do this, I am injecting newly emerged bees from each stock with DWV and determining virus titer levels in various body parts over time. Additionally, I am checking these stocks for their overall mite levels corresponding DWV titer levels throughout the year. In the coming year, I plan on adding in a nutritional-component in order to look at genetic, virus, and foraging preference interactions.
I am working in collaboration with the Crist lab at Miami University to determine how spider species beta-diversity in temperate forest canopies partitions across spatial scales. Using samples collected via canopy fogging, we are parsing out potential mechanisms such as tree species preference, intraguild conflicts with ants, availability of prey items, and surrounding land use. I am also working with Michael Mahon and Michael Minnick to create an R package to partition diversity in lieu of older software (Github: mahonmb/PARTITIONR).
After listening to symposia in 2014-0215 where individuals would discuss the costs and benefits of neonicotinoid seed treatments, I wanted to look into how these treatments impacted ants in agricultural areas since they are often used as an indicator group. The thought process behind this was that seed treatments may leach into the surrounding soil, where ants nest, and potential cause both sub-lethal and lethal effects. I was fortunate enough to have the help of an undergraduate student – Andrew Dale – in order to complete both a lab toxicity trial and a field experiment where we monitored ant community composition and their predation services. We ended up using seeds treated with fungicide as that was common in Kentucky (our area of study at the time) with some also being treated with imidacloprid.
We found that both fungicide only treatments and the fungicide/imidacloprid combination caused increased levels of intoxicated behavior and mortality in the ants. However, both in the lab and the field, we saw no effects of imidacloprid on foraging effectiveness. The ant community did exhibit some differences in the field with pavement ants (Tetramorium caespitum) being less abundant in fields where we used neonicotinoid-treated seeds, resulting in an increase in ant species richness.
Throughout the past few years, I’ve been working closely with agricultural economists (Jerrod Penn and Wuyang Hu) to determine both public and stakeholder knowledge and opinions of various entomology topics. The first foray into surveys was to determine hotel consumer knowledge and preferences about bed bug policies with UKY’s Mike Potter. This was a pretty successful venture and was even featured in the ScientificAmerican podcastand the New York Times. Since then, we have completed a survey on public knowledge of monarch conservation and are currently working on a general public, university student, and beekeeper knowledge of pollinators surveys (with undergraduate Macy Hagan) and a grower best management practice survey (with Michael Minnick at Miami University).