Silica bodies and their systematic implications in Pteridaceae (Pteridophyta)

Abstract

Wet ashing was used to study the occurrence of silica bodies in the fern family Pteridaceae. They were recovered in 48 of the 77 species examined. Silica bodies of Pteridaceae are elongate, ranging from 90–1320 × 5–40 µm, linear to elliptic, with blunt or acute apices and smooth to sinuate sides. All previous records of silica bodies and venuloid idioblasts among Pteridaceae that were examined were confirmed by the results of this study, corroborating our assumptions regarding the presence of silica bodies. In contrast, assumptions regarding the absence of silica bodies were incorrect; in many species of Adiantum, for example, silica bodies are present but cannot be seen with the naked eye. Farris optimization demonstrates that the distribution of epidermal silica bodies is homoplastic within Pteridaceae, but that they act as a potential synapomorphies for several different groups within the family. These include the adiantoid clade: Adiantum and the 11 vittaroid genera, and in some pteridoid fern clades such as the sister pair Onychium and Actiniopteris and the genus Pityrogramma. They are also present in Pterozonium brevifrons and some species of the polyphyletic genus Pteris. Among cheilanthoid ferns, they were found in Mildella intramarginalis and two species of Aspidotis. Morphology of silica bodies differs between major lineages, reflecting their independent origins. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161, 422–435.