A Brief Review of Phytochemical Defenses of Ferns against Herbivores

Ferns have been exposed to herbivorous insects since the latter evolved in the Devonian. Currently, ferns suffer similar percentages of leaf herbivory as angiosperms. Therefore, they often use a combination of chemical defenses as protection against herbivores. In this review, we summarize the distribution of five groups of biomolecules that may act as chemical defenses of ferns: phytoecdysteroids, flavonoids, thiaminase, cyanogenic glycosides, and alkaloids. For each of these biomolecules, we briefly discuss their biosynthesis, mode of action, and currently known taxonomic distribution in ferns, and include examples to illustrate their observed concentrations in different fern tissues. We conclude with a discussion of ferns that accumulate heavy metals, which may also serve in their defense against herbivores. Finally, we discuss research gaps to encourage future research in this widely understudied and ecologically important field of investigation.

Automated summary

Ferns have developed chemical defenses to protect against herbivorous insects. This review summarizes the distribution and characteristics of five groups of biomolecules that act as chemical defenses in ferns. The review also discusses the accumulation of heavy metals in ferns as another defense mechanism. Future research in this ecologically important field is encouraged.