In order to manage farming methods with fewer or no pesticides, researchers from the University of Michigan emphasize the need to grasp how ecological systems operate on agricultural terrain.
Currently, U-M scholars John Vandermeer and Ivette Perfecto have applied two ecological theories to elucidate a complex web of encounters involving three ant species and a newly introduced fly that preys on one of the ant species. Their research on a coffee plantation in Puerto Rico reveals that the interaction between the ants and the predatory fly generates chaotic dynamics—chaos in the traditional sense, where natural populations experience variations based on the interactions among organisms within a system.
These chaotic dynamics imply that any one of the four insect species could dominate at any given moment. Understanding which ants might take the lead over time could assist farmers in leveraging the ants to manage pests effectively. Their research, backed by the National Science Foundation, is featured in the Proceedings of the National Academy of Sciences.
“Two of the three ant species we examined play crucial roles as biological control agents for two significant pests in coffee,” stated Vandermeer, U-M professor of ecology and evolutionary biology. “Farmers would benefit from the ability to predict when the ants will be present and when they will not. Unfortunately, making such predictions is quite challenging.”
For three decades, Vandermeer and Perfecto, a professor at the U-M School for Environment and Sustainability, have been researching ant interactions within the coffee farm’s agricultural environment. Their objective is to assist in overhauling agricultural methods, but to achieve this, they assert that comprehending the ecology of farming systems is essential.
“Our stance is that the present global agricultural framework, characterized by the use of pesticides and chemicals, fails to benefit anyone, particularly the farmers, and significantly contributes to global climate change,” Vandermeer remarked. “To effectively integrate ecological principles into the development of innovative agricultural practices, we must first understand those principles and their functions.”
In tropical regions, ants are prevalent, Vandermeer notes, and frequently act as pest control agents. However, deploying an ant species for pest management can be intricate: the supremacy of the ant utilized depends on the presence of other ant species and various types of insects within the system.
Within this framework, Vandermeer and Perfecto explored two forms of ecological behavior: intransitive loop cyclic behavior and predator-mediated coexistence. Intransitive loop cyclic behavior indicates that in a group of three ant species, Ant A may dominate Ant B, Ant B might prevail over Ant C, but Ant C could subsequently outperform Ant A.
Introducing a predator complicates these dynamics further. Among the three ant species under scrutiny by Vandermeer and Perfecto, one species holds dominance. However, the newly introduced fly targets the dominant ant. This predator-prey interaction not only influences the dominant ant but also affects the other two ant species, enabling any of the four species to rise as the dominant one at different moments. This exemplifies predator-mediated coexistence.
The fluctuations of the predatory fly and its ant target, alongside the changes in ant dominance, are referred to as oscillations. By integrating and modeling these two oscillating ecological phenomena, the researchers were able to investigate how these principles introduce chaos into the system.
The outcomes are indeed chaotic. By mapping both of these oscillating behaviors, the researchers discovered that at specific intervals, the entire system resembled a predator-prey cycle, while at other times, it appeared as an intransitive loop oscillation.
Theoretically, this could provide the researchers with insights into when each insect species would become dominant.
“The positive aspect is that the chaotic behaviors of the insects are inherently fascinating from an intellectual viewpoint. The downside is that developing agricultural practices based on ecological principles may not be as straightforward as it appears since the ecological principles themselves are significantly more complex than merely identifying a pesticide that eradicates the pests,” Vandermeer stated.
“Through our discoveries over the last 30 years, we believe we are uncovering several of the complications that arise when one genuinely strives to integrate ecology into the fundamental operations of the agricultural system.”