Phytochemical diversity impacts herbivory in a tropical rainforest tree community

Metabolomics provides an unprecedented window into diverse plant secondary metabolites that represent a potentially critical niche dimension in tropical forests underlying species coexistence. Here, we used untargeted metabolomics to evaluate chemical composition of 358 tree species and its relationship with phylogeny and variation in light environment, soil nutrients, and insect herbivore leaf damage in a tropical rainforest plot. We report no phylogenetic signal in most compound classes, indicating rapid diversification in tree metabolomes. We found that locally co-occurring species were more chemically dissimilar than random and that local chemical dispersion and metabolite diversity were associated with lower herbivory, especially that of specialist insect herbivores. Our results highlight the role of secondary metabolites in mediating plant-herbivore interactions and their potential to facilitate niche differentiation in a manner that contributes to species coexistence. Furthermore, our findings suggest that specialist herbivore pressure is an important mechanism promoting phytochemical diversity in tropical forests. We leveraged these innovations in untargeted metabolomics to study the foliar metabolomes of 358 tree species to evaluate the interaction between the abiotic environment, metabolite diversity, and herbivore damage due to specialist and generalist insect herbivores. Our results suggest that plant neighbourhoods with diverse secondary metabolites reduce the rate of damage by herbivores, especially specialist herbivores with limited host ranges and the potential for density-dependent impacts on plants. The role of specialist herbivores in promoting local neighbourhoods of chemically dissimilar and diverse trees suggests that chemically mediated plant-herbivore interactions represent a key component of the niche with the potential to contribute to the maintenance of tree species diversity in tropical forests.image

Automated summary

Metabolomics is a powerful tool to study the chemical composition of plants and its relationship with various factors in tropical forests. This study found that tree metabolomes rapidly diversify and locally co-occurring species are more chemically dissimilar. The presence of diverse secondary metabolites can reduce herbivore damage, especially by specialist insect herbivores.