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Scientists have long studied the enthralling arms race between plants and their natural enemies. Yet, with the overwhelming intricacies of these interactions, several questions remain unanswered. Our very own Department of Biological Sciences Assistant Professor, Dr. Diego Salazar Amoretti,  attempts to answer one such question in a unique study conducted in an Amazon rainforest.

Through his research with our International Center for Tropical Botany and the Plant Chemical Ecology Lab, Salazar and his team successfully executed one of the most comprehensive evaluations of the chemistry of any tree genus to date, with the aim of investigating the origin and maintenance of chemical diversity in a species-rich tropical tree lineage.  

This research, Salazar explains, not only deepens our knowledge of the natural world, but it also offers the potential of improvements to our day-to-day lives.  

“In spite of the vast knowledge we have today on the diversity of organisms, their distributions, ecology, and evolution, we know very little of the diversity, distribution, function, and evolution of the natural compounds produced by said organisms. We believe that a deeper understanding of these topics is fundamental to, not only reaching a better understanding of the processes that forge and maintain the vast diversity of the natural world, but also to create better strategies for the discovery and development of novel medicines, pesticides, and the improvement of staple crops, ” urges Salazar.

Given that plants face diverse communities of herbivore species, each armed with distinct sets of adaptations, the question remains: How do plant chemical defenses evolve under such varying conditions? Salazar tackled this question by characterizing the chemical diversity and insect herbivore fauna from 31 geographically overlapping species of Amazonian Protieae trees, differentiating and quantifying close to 600 putative secondary metabolites among these species.

Secondary metabolites are compounds not linked to the plant’s primary metabolism, and they are often instrumental in a plants’ defense from herbivores. Comprising up to half of a plant’s dry weight, it is currently believed that these secondary metabolites are largely responsible for the immense diversity observed among plant species. As herbivores overcome or even begin to exploit such metabolites, their net evolutionary value is lost and plants must then adapt yet again, creating this pairwise coevolutionary arms race.  

While most research has focused efforts on the interaction of a single class of metabolites across a small group of plant and herbivore species, Salazar conducted a detailed large-scale study of the chemical diversity and plant-herbivore interactions in order to account for the multitude of herbivore species faced by plants. What he and his team found is that the net evolutionary advantage offered by specific secondary metabolites depends primarily on its cumulative effect across all herbivores, rather than their effect on specific species.

Published in Nature Ecology & Evolution, this study offers robust and compelling evidence for the role of plant-herbivore interactions on the evolution of plant chemical diversity and opens the door for future studies to build upon this knowledge.

Learn more about Salazar’s study here.