Evolution of phytolith deposition in modern bryophytes, and implications for the fossil record and influence on silica cycle in early land plant evolution

• Published in: The New phytologist Vol. 221; no. 4; pp. 2273 - 2285
• Main Authors: Thummel, Ryan V., Brightly, William H., Strömberg, Caroline A. E.
• Format: Journal Article
• Language: English
• Published: England Wiley 01.03.2019; Wiley Subscription Services, Inc
• Subjects: Accumulation; Aquatic plants; Bioaccumulation; Biological Evolution; Bryophyta; Bryophyta - physiology; Bryophytes; Conductance; Deposition; Diagnostic systems; disease diagnosis; early land plants; embryophytes; Evolution; Fossils; Freshwater plants; Germ Cells, Plant - physiology; Marchantiophyta; morphs; Mosses; mosses and liverworts; paleobotany; phylogeny; phytoliths; Resistance; Rhizoids; Silica; silica cycle; Silicon dioxide; Silicon Dioxide - chemistry; Surveying; surveys; Tissue; tissues; water conductance; silica cycle; paleobotany; phytoliths; early land plants; bryophytes; water conductance
• ISSN: 0028-646X; 1469-8137; 1469-8137
• DOI: 10.1111/nph.15559

• Anecdotal evidence indicating substantial silica accumulation in tissues of bryophytes suggests that silica (phytolith) deposition evolved early on in embryophytes. To test this hypothesis, we conducted the first survey of phytolith content representing the major liverwort, moss and hornwort clades. We also assessed the diagnostic value of bryophyte phytoliths. • Silica extracted from bryophyte material through wet-ashing was described, focusing on abundance, classifying taxa as nonproducers, light producers and higher producers; and phytolith morphotypes. Ancestral state reconstruction of these characters was performed for mosses and liverworts using published phylogenies. • Phytoliths are present in multiple subclades within liverworts, mosses and hornworts, but these phyla were not ancestrally high silica-producers. Higher deposition occurs in liverworts and mosses with specialized water-conducting cells. • We hypothesize that active, high silica accumulation was not ancestral for embryophytes, but became possible in clades with increased water conductance. Phytoliths of diagnostic structures (e.g. pegged rhizoids) could help track bryophyte clades or water conductance evolution in the fossil record.