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The Botanical Review

, Volume 74, Issue 3, pp 438–466 | Cite as

Pollen and the Evolution of Arctotideae (Compositae)

  • Alexandra H. Wortley
  • V. A. Funk
  • John J. Skvarla
Article

Abstract

Recent molecular studies have elucidated the phylogeny of Compositae tribe Arctotideae, and found it to contain two, well supported, monophyletic subtribes, Arctotidineae and Gorteriinae, as well as some polyphyletic and problematic genera. On the basis of this new information, it may now be possible to identify diagnostic characters and synapomorphies to support the groupings defined within Arctotideae. Pollen characters have been shown to be particularly variable in Compositae. This paper aims to investigate the utility of those characters in the context of recent molecular phylogenies, in order to determine synapomorphic and diagnostic characters in Arctotideae. The pollen of each genus is described, illustrated with scanning electron micrographs, and optimised on a phylogeny of the tribe. Many pollen characters were found to be very informative when considered in the context of the current best estimate of phylogenetic relationships. Pollen morphology provides synapomorphies for clades at a number of hierarchical levels within Arctotideae, including the two subtribes, Arctotidinae and Gorteriinae, the grouping of Eremothamnus and Hoplophyllum, and smaller clades. It also supports the exclusion of Platycarpha from the tribe. The plesiomorphic palynological state for the tribe is discussed. Particular attention is paid to the evolution of different patterns of lophae (surface ridges). A single origin for the lophate condition is proposed as the most parsimonious mode of evolution in Arctotideae.

Keywords

Arctoteae Arctotidinae Asteraceae Characters Gorteriinae Palynology Phylogeny 

Notes

Acknowledgements

The authors would like to thank Gregory Strout, especially, and William Chissoe for their help with electron microscopy and plate preparation, Marinda Koekomoer (PRE) for sending material, Harold Robinson (US) for helpful discussions and Mike Dillon for commenting on an earlier version of this manuscript.

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Copyright information

© The New York Botanical Garden 2008

Authors and Affiliations

  • Alexandra H. Wortley
    • 1
  • V. A. Funk
    • 2
  • John J. Skvarla
    • 3
  1. 1.Royal Botanic Garden EdinburghEdinburghUK
  2. 2.U.S. National Herbarium, Smithsonian Institution MRC 166WashingtonUSA
  3. 3.Department of Botany–Microbiology and Oklahoma Biological SurveyUniversity of OklahomaNormanUSA

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