Metabolomic Diversity and Defensive Phenolic Compounds in Cloud Forest Ferns

The few current metabolomic studies on ferns are mostly restricted to a single species or focused on specific compounds. We performed an untargeted metabolomic study on six of the most common fern species from the cloud forest, followed by a targeted analysis of 64 phenolic compounds, many of which have been associated with herbivore defense. The untargeted analysis revealed a total of 232 putative identified metabolites from 463 to 1427 signals per fern species, each with its proper chemical signature but not necessarily correlated to their phylogenetic relationship. The flavonoid, flavone, and flavonol biosynthesis were the most expressed pathways in all species except for Marattia laxa. Fern species also differed strongly in the concentrations of the 10 detected phenolic compounds. Our results show that ferns, including the most ancestral species, such as M. laxa, display a high metabolomic diversity comparable to seed plants. Each fern species held a different combination of defensive phenolic compounds. Further research is needed to explore the metabolic diversity, to identify the biochemical defenses of ferns, and, in particular, to detect the chemical compounds that act against their specific herbivorous insects in the cloud forest ecosystem.