Influence of phylogenetic diversity of plant communities on plant-herbivore-natural enemies interactions

Phylogenetic diversity of plant communities can influence the interaction between plants, herbivores and their natural enemies. Plant communities with phylogenetically distant species tend to present a wide variety of functional traits and ecological niches, which in turn can influence competitive interactions among plants as well as food and habitat quality for herbivores and their natural enemies. To assess the different mechanisms by which phylogenetic diversity of plant communities may influence herbivores and their natural enemies, we established 12 experimental plots of tropical trees with two treatments: high and low phylogenetic diversity. We measured plant growth, and anti-herbivore defenses, herbivore foliar damage, and predator activity in seven species that were present in both treatments. We found significant differences in the expression of plant traits as a function of species identity and their life history, but also depending on the phylogenetic context in which they grew. Pioneer species had higher growth and greater phenolic levels in plots with high phylogenetic diversity, versus plants in plots with low phylogenetic diversity. Herbivore damage was higher in plots with low phylogenetic diversity, where pioneer plants produced less defenses. Finally, predator activity on clay models was greater in plants within the low phylogenetic diversity treatment, but only for non-myrmecophytic species. These results suggest that plant phylogenetic diversity can influence species resource allocation for growth and defenses, and further modify the interaction between plants, herbivores, and their natural enemies. Moreover, such effects likely depend on plant life history and the presence of mutualistic interaction with ants.