An Evolutionary and Ecological Perspective of the Insect Fauna of Ferns

Analysis of the number and distribution of insects attacking ferns demonstrates that significantly fewer insects than expected utilize ferns as a food source. Also, insects which do attack ferns are not a representative sample of phytophagous insects in general. Analysis of the feeding habits of these insects indicates that few families or even genera of insects have specialized on ferns. Juxtaposition of the evolutionary histories of ferns and phytophagous insect groups fails to adequately explain the anomalies seen, since evolutionarily old groups are no better represented on ferns than younger groups. Differences in morphological complexity between angiosperms and ferns (primarily lack of flowers) probably accounts for a portion of the underutilization of ferns, but chemical defense mechanisms and ecological characteristics such as population size or phenology may be of importance. The present insect fauna of ferns appears to have been derived from insects utilizing woody plants via host-plant switching.