AOBPreview originally published online on May 9, 2009
Annals of Botany 2009 104(1):91-113; doi:10.1093/aob/mcp097
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Phytoliths in woody plants from the Miombo woodlands of Mozambique
1 Department of Archaeology, University of Calgary, 2500 University Drive N.W., Calgary, Alberta, T2N 1N4, Canada
2 Environics Research Group, 999 8 Street S.W., Calgary, Alberta, T2R 1J5, Canada
* For correspondence. E-mail Mercader{at}ucalgary.ca
Received: 23 February 2009 Returned for revision: 17 March 2009 Accepted: 19 March 2009 Published electronically: 9 May 2009
Background and Aims: There are no descriptions of phytoliths produced by plants from the ‘Zambezian’ zone, where Miombo woodlands are the dominant element of the largest single phytochorion in sub-Saharan Africa. The preservation of phytoliths in fossil records of Africa makes phytoliths a tool to study early plant communities. Paleo-ethnobotanical interpretation of phytoliths relies on the comparison of ancient types with morphotypes extracted from living reference collections.
Methods: Phytoliths were extracted from plant samples representing 41 families, 77 genera and 90 species through sonic cleaning, dry ashing and acid treatment; and phytoliths thus extracted were quantified. For each species, an average of 216 phytoliths were counted. The percentage of each morphotype identified per species was calculated, and types were described according to the descriptors from the International Code for Phytolith Nomenclature. Phytolith assemblages were subject to discriminant analysis, cluster analysis and principal component analysis.
Key Results: Phytoliths were grouped into 57 morphotypes (two were articulated forms and 55 were discrete shapes), and provide a reference collection of phytolith assemblages produced by Miombo woody species. Common and unique morphotypes are described and taxonomic and grouping variables are looked into from a statistical perspective.
Conclusions: The first quantitative taxonomy of phytoliths from Miombos is presented here, including new types and constituting the most extensive phytolith key for any African ecoregion. Evidence is presented that local woody species are hypervariable silica producers and their phytolith morphotypes are highly polymorphic. The taxonomic significance of these phytoliths is largely poor, but there are important exceptions that include the morphotypes produced by members from >10 families and orders. The typical phytolithic signal that would allow scientists to identify ancient woodlands of ‘Zambezian’ affiliation comprises only half of the original number of phytoliths originally produced and might favour the more resilient blocky, cylindroid, globular and tabular forms.
Key words: Africa, Mozambique, Niassa, Miombo, phytolith analysis, reference collection, quantitative methods, principal component analysis, cluster analysis, discriminant analysis
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