Are two biological control agents always better than one?
Contributed by Ash Zemenick @mtn_ash & Ivette Perfecto
Agriculture, Agroecosystem, Animals, Caribbean, Community ecology, Competition, Consumption, Ecology, Field, Interactions, Latino/a/x, Natural history, Observational, Plants, Predator-Prey, Puerto Rican, Race/ethnicity, Woman
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Ivette Perfecto and John Vandermeer. 2018. Antagonism between Anolis spp. and Wasmannia auropunctata in coffee farms on Puerto Rico: Potential complications of biological control of the coffee berry borer. Caribbean Journal of Science, 50(1): 43-47 link
Slide 1: Researcher’s Background
Ivette Perfecto is a George W. Pack Professor of Ecology, Natural Resources, and the Environment at the University of Michigan, Ann Arbor. She is an ecologist who studies biodiversity and species interactions in agricultural systems. She is a researcher, author, and advocate for food sovereignty and sustainable agriculture.
PB: Why did you become a biologist?
IP: Growing up in Puerto Rico I became fascinated by the beauty of marine organisms and enraged about how pollution was affecting marine ecosystems. That led to a degree in biology, and eventually graduate work in ecology. Living in the oldest colony in the world, I developed a critical view of the impacts of US colonialism on my island and that is why I decided to focus on environmental studies.
PB: What is your favorite part about your job?
IP: I love being in the field and trying to understand how nature works. I also love interacting with students and seeing them grow intellectually and become independent scientists.
PB: What obstacles have you overcome to get where you are?
IP: When I started graduate school I was a single mother. I had just moved from Puerto Rico to Michigan with my 2-year old son. Life was hard, but at the same time fascinating. I was being exposed to many new ideas, both in biology as well as in politics. Life was exciting and I felt that I shouldn’t waste time dwelling on problems but just overcome them as best as I could. As I matured politically and became more aware of my position as a female and Latinx scientist I realized, in retrospect, that I had been subject to discrimination. That made me even more determined to be a better teacher and a better scientist. Also, I never attempted to do this alone. I was always surrounded by comrades that helped and supported me along the way.
PB: What advice do you have for aspiring biologists?
IP: Don’t dwell on problems and obstacles that may emerge during your career. Just tackle them up front and as best as you can and move on. It is also important to surround yourself with friends and colleagues that are in solidarity with you.
PB: Do you feel that any dimension of your identity is invisible or under-represented/marginalized in STEM?
IP: Yes. There are not many Latinx women in STEM, and in particular in ecology.
Slide 2: Research Overview
Take home message of study
Are two biological control agents always better than one? Ivette Perfecto and John Vandermeer set out to answer this question studying two different predators (Anolis lizards and Wasmannia ants) of an often devastating pest of coffee plants, the coffee berry borer (Hypothenemus hampei). After surveying coffee bushes in 11 different farms in Puerto Rico, they found that areas of coffee farms dominated by Wasmannia ants have much lower abundance of anolis lizards. Ivette and John concluded that, “If anoles should be more efficient than the ants then high densities of the ants must be regarded as a negative effect on biological control, despite their clear predatory behavior. This would clearly represent a rejection of the idea of multiple predators as a “resilient” or “sustainable” strategy for pest control for this particular situation.”
The study was performed in coffee farms in the central highlands of Puerto Rico. The focal species of the study were Anolis lizards (top panel; photo source) and Wasmannia auropunctata ants (bottom left panel; photo source) – both predators of the coffee berry borer (bottom right panel; photo source)
Anolis lizards are common occupants of coffee farms. Because the removal of Anolis lizards has resulted in increased numbers of the coffee berry borer (CBB), it is likely that they are predators of the CBB and play an important role in biological control of that pest.
Little fire ants, Wasmannia auropunctata, are also important predators and biological control agents of the CBB. However, their aggressive nature might also negatively impact Anolis lizards (which is what Ivette set out to understand in this study).
Slide 3: Key Research Points
This figure shows the percent of coffee bushes surveyed that were occupied by Wasmannia auropunctata ants (x-axis) or Anolis lizards (y-axis). In general, areas in coffee farms that have high densities of Wasmannia auropunctata have lower densities of Anolis lizards.
Caption from paper: “Relationship between the ant, W. auropunctata and anoles at the 11 sites in this study. Regression significant at the p = 0.01095 level with an R2 = 0.53.”
Understanding the ecology of biological control agents is critical to manage crop pests in a sustainable manner and reduce our reliance on agrochemicals for pest control. It is also important to understand the impacts of invasive species on the ecosystems they invade. This study is important because it examines the impact of an invasive ant on the potential biological control services provided by anolis lizards. While theoretically it might seem better to have multiple biological control agents to control a pest, this may not always be the case if they impede each other’s ability to control the pest. This study points to the importance to have a full, nuanced understanding of the ecology of biological control in agroecosystems.