Biochemical and evolutionary aspects of arthropod predation on ferns

The widely held assumption that very few arthropods feed on ferns was questioned following field observations of arthropod damage on ferns in the state of Veracruz, Mexico. The extent and type of damage was recorded and it was found that in a measured locality, ferns were no less attacked than the angiospermous flora. As chemistry and arthropod host relationships have been shown to be so closely intertwined, plants collected in the field were analysed for both condensed tannins and cyanogenic glycosides, compounds known to be effective deterrents in temperate climates. Although all ferns tested contained tannins these did not appear to inhibit predation. Cyanogenic glycosides were present in only 3% of the fern species analysed, and it is, therefore, unlikely that they play a significant role as defensive compounds in the ferns examined.A literature search revealed a large number of ferns cited as being arthropod hosts. Approximately 420 named species of arthropods have been recorded, the majority of which are from the orders Coleoptera, Hymenoptera, Lepidoptera, and Hemiptera. Both evolutionary primitive (sawflies) and advanced (moths) arthropods are reported to be present on ferns suggesting possible coevolution of arthropods and ferns both before and after the radiation of angiosperms.