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SYSTEMATIC AND ECOLOGICAL SIGNIFICANCE OF SEED COAT MORPHOLOGY IN SOUTH AFRICAN CAMPANULACEAE SENSU STRICTO

Published online by Cambridge University Press:  18 October 2011

C. N. Cupido ,
W. M. M. Eddie  and
L. R. Tiedt
C. N. Cupido
Affiliation:
South African National Biodiversity Institute, Compton Herbarium, Private Bag X7, Claremont 7735, South Africa. E-mail: [email protected]
W. M. M. Eddie
Affiliation:
Office of Lifelong Learning, University of Edinburgh, 11 Buccleuch Place, Edinburgh EH8 9LW, Scotland, UK. E-mail: [email protected]
L. R. Tiedt
Affiliation:
Laboratory for Electron Microscopy, University of the North West, Private Bag X6001, Potchefstroom 2520, South Africa. E-mail: [email protected]
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Abstract

The seed coat morphology of 50 species of Campanulaceae sensu stricto, representing all 10 South African genera, was studied by scanning electron microscopy to gauge its usefulness in the diagnosis of genera or to support clades. Possible correlations with life form (annual, herbaceous and woody perennial) and ecological requirements such as fire response, rainfall requirements, bedrock and soil preferences, as well as habitat (e.g. fynbos, strandveld, renosterveld, grassland and karoo), were also investigated. Patterns of variation are described and interpreted as conforming to two seed coat types: reticulate (Type 1) and striate/wavy (Type 2). Type 1 seeds are further divided into eight subtypes. Some general trends emerged; for example, Type 1 seeds occur in all major clades of wahlenbergioids, Type 1A with a smooth coarsely reticulate surface being predominant in fynbos taxa, all of which are woody perennials. Several of the Type 1 seeds, together with Type 2 seeds, also occur in species with wider ecological amplitude, for example in karoo, strandveld or montane grasslands. In Siphocodon there is remarkable disparity in seed type between species. These variations in seed type generally appear to accord with current knowledge of climatic changes and soil evolution during the Tertiary of South Africa, and may be useful indicators of generic emergence and mosaic speciation in the major lineages of wahlenbergioids. However, it was concluded that seed coat types do not correlate closely enough with specific ecological requirements or life forms to be of unequivocal predictive value. Also, apart from Merciera and Treichelia, they are of limited use as a diagnostic character for genera, but are useful for distinguishing species.

Keywords

Phylogenyscanning electron microscopytaxonomyvegetation typesWahlenbergiawahlenbergioid
Type
Articles
Information
Edinburgh Journal of Botany , Volume 68 , Issue 3 , November 2011 , pp. 351 - 371
Copyright
Copyright © Trustees of the Royal Botanic Garden Edinburgh 2011

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