Sundue, Michael .
Silica bodies and their systematic implications in the Pteridaceae.
Discrete isotropic cellular inclusions of SiO2-nH2O, referred to as silica bodies or phytoliths, are known to occur at least sporadically within all major groups of vascular plants and have been relied upon as a diagnostic and systematic character. Silica bodies within monocots have received considerable attention, but those occurring in many other groups remain to be studied. Silica bodies are evaluated here as a systematic character in the fern family Pteridaceae. Silica bodies have been studied in the Pteridaceae at least since Poirault’s anatomical studies of 1897, but a family wide survey has never been undertaken, and their distribution has not been considered in light of recent phylogenetic studies. No morphological or anatomical synapomorphies are known for the Pteridaceae, and possible morphological synapomorphies for the five major clades of the family are few or lacking. Thus the identification of diagnostic characters for use at higher levels within the family fills a critical gap in knowledge. Using wet ashing, silica bodies were recovered in 48 of the 77 species examined. The distribution of epidermal silica bodies is homoplastic within the Pteridaceae, but is a potential synapomorphy for several groups including the adiantoid ferns (Adiantum + 11 vittarioid genera), Onychium + Actiniopteris, Pityrogramma, Aspidotis, and portions of the polyphyletic genus Pteris. Morphology of silica bodies differs between major lineages, reflecting their independent origins. The position of silica bodies within leaves is also a potential synapomorphy for the Adiantum tetraphyllum group, a natural group of 20–25 species.
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1 - The New York Botanical Society, Institute for Systematic Botany, 200th St. and Southern Blvd., Bronx, NY, 10458, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Alpine B/Snowbird Center
Date: Monday, July 27th, 2009
Time: 10:15 AM