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 co-existence.
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 rain forest 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 was 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.