Research in Fiji Reveals How Host Plants Manage Ant Conflicts

In a groundbreaking study published on July 10, 2025, scientists from Washington University in St. Louis and Durham University in the United Kingdom revealed how the Squamellaria plant species in Fiji maintains harmony among rival ant species that inhabit its chambers. This research highlights the significance of compartmentalization as an evolutionary strategy, offering insights into mutualistic relationships in ecological systems.

The study, led by Guillaume Chomicki, a researcher at Durham University, demonstrates that the Squamellaria plant creates separate chambers within its tuberous structure, allowing different ant species to coexist without conflict. Each chamber has its own entry point, preventing direct competition for resources. Chomicki noted, "Our study shows that compartmentalization is one solution to the conflicts that could arise among ant residents. The more ants that live inside a tuber, the more nutrients for the plant."

Historically, mutualistic relationships tend to be beneficial for both species involved, but such interactions can also lead to competition and conflict, especially among unrelated partners. The research indicates that Squamellaria's structural adaptations actively mitigate these risks. Susanne S. Renner, a biologist in Arts & Sciences at Washington University and senior author of the study, emphasized the importance of field observations, stating, "One needs to see and identify the ants to understand the significance of the compartments."

Chomicki and Renner's investigation began during a field excursion in the Waisali Rainforest Reserve, where they discovered multiple ant colonies inhabiting a single Squamellaria plant. Through a series of experiments, including the removal of partition walls between chambers, they documented intense conflict among ant species that were previously isolated. The conflict resulted in high mortality rates among the ant workers, underscoring the necessity of the compartmentalization mechanism.

The researchers employed advanced computed-tomography scanning to visualize the internal structure of the Squamellaria tubers, a technique that is rarely utilized in botanical studies. This method was crucial in confirming the existence of separate chambers and informing their conclusions about the ecological dynamics at play. Renner remarked, "Here we visualize what theory has long predicted: that unrelated partners would conflict over resources, but the Squamellaria plant has developed an effective evolutionary strategy to mitigate these conflicts."

This study not only expands the understanding of plant-insect interactions but also poses broader ecological questions regarding the evolution of mutualistic relationships. By offering a clear example of how environmental factors can shape symbiotic behavior, the findings may have implications for biodiversity conservation and ecosystem management practices in similar habitats worldwide.

As researchers continue to explore the complex dynamics of symbiosis in nature, the Squamellaria and its resident ants serve as a model for understanding the intricate balance of cooperation and competition in ecological relationships. The ongoing study of such interactions is essential for developing strategies aimed at preserving biodiversity and ecosystem functionality in the face of environmental changes.

Reference: Chomicki, G., Metzler, D., Naikatini, A., & Renner, S. S. (2025). Compartmentalization reduces conflict in multipartner plant-insect symbioses. Science. doi: 10.1126/science.adu8429