Macrosiphum on ferns: taxonomy, biology and evolution, including the description of three new species (Hemiptera: Aphididae)

Summary The phytophagous insect fauna of ferns has often been described as depauperate, and some have pointed to the paucity of evidence for adaptive radiation of insect groups feeding specifically on ferns. This paper examines the world's species of fern‐specific Macrosiphum aphids and attempts to determine whether fern‐feeding is a monophyletically derived trait in Macrosiphum . All sixteen species reported to feed on ferns, including three new species, were included in a cladistic analysis, along with fifteen other Macrosiphum species selected to represent the diversity of the genus, Papulaphis sleesmani (Pepper), because of its similarity to fern‐feeding Macrosiphum , and Sitobion avenae (Fabricius), which was used as outgroup. The results gave good support for the monophyly of fifteen of the sixteen fern‐feeders, and also supported a clade consisting of these fifteen fern‐feeders plus Macrosiphum equiseti (Holman), an Equisetum ‐specific aphid. One species, Macrosiphum lapponicum Shaposhnikov, from northern Russia, was concluded to be unrelated to other fern‐feeding Macrosiphum . Whether this species truly feeds on a fern requires confirmation. Taxonomic and biological notes are provided for all fern‐feeding Macrosiphum of the world. These include one new combination, Macrosiphum cyatheae (Holman) comb.n., and three new species: Macrosiphum longirostratum sp.n. on Woodsia mollis and Woodsia sp. from Mexico (Michoacán), Macrosiphum miho sp.n. on ‘ Aspidium ’ sp. from the U.S.A. (Illinois) and Macrosiphum rebecae sp.n. on Adiantum sp. from Mexico (Michoacán). Keys to apterous and alate viviparae of Macrosiphum living on ferns are given.