Uncovering the evolution of a surprisingly pleasant defense strategy of ferns

Plants and the animals that eat them have evolved together in fascinating ways, creating a dynamic interplay of survival strategies. Many plants have developed physical and chemical defenses to deter herbivores. A well-known strategy in flowering plants is to produce nectar to attract „ant bodyguards”. Recent research examines the evolution of this same defense strategy in ferns.

Jacob Suiza, an assistant professor at the University of Tennessee Knoxville, led the study along with Fern expert Fei-Wei Li of the Boyce Thompson Institute and Cory Morrow, an ant expert at Cornell University.

study, recently Published Inside Natural communication, ferns and flowering plants independently developed nectaries, specialized structures that secrete sugar rewards to attract ant bodyguards, at the same time during the Cretaceous. The discovery is significant, suggesting that similar evolutionary dynamics shaped the development of ant-plant mutualism in these two divergent lineages, separated by more than 400 million years.

„Our research highlights a fascinating example of convergent evolution in which ferns and flowering plants have developed similar strategies to defend themselves against predation by adding ant guards to nectaries,” Suiza said.

Combining phylogenetic data and comparative analyses, the research team found that nectaries appeared simultaneously in ferns and angiosperms, but that ferns experienced a significant lag in diversification compared to their flowering plant counterparts. The study suggests that ferns may have recruited ant protectors secondarily, tapping into pre-existing ant-angiosperm relationships as they transition from the forest floor to the canopy.

„The evolutionary history of fern nectaries not only demonstrates the complex relationships between plants and insects—relationships previously underestimated—but also underscores the ability of ferns to adapt to environmental challenges,” Suiza explained.

The research provides new insights into the evolutionary dynamics that shape plant-animal interactions. By understanding how ferns and flowering plants develop similar defense mechanisms, scientists can better appreciate the basic principles that govern biodiversity and ecosystem function. The study reinforces the importance of mutualistic relationships in the natural world and opens new avenues for investigating the evolutionary history of other plant traits and their ecological impact.