Pollen and the Evolution of Arctotideae (Compositae)
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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.
KeywordsArctoteae Arctotidinae Asteraceae Characters Gorteriinae Palynology Phylogeny
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.
- ——— 2000. The palynological compass: the contribution of palynology to systematics. Pp. 161–177 in B. Nordenstam, G. El-Ghazaly & M. Kassas (eds.), Plant Systematics for the 21st Century. Portland, London.Google Scholar
- ——— A. H. Wortley, J. J. Skvarla & H. Robinson. 2008. Evolution of pollen in the Compositae. Proceedings of the International Compositae Alliance, Barcelona, 2006. In Systematics, Evolution and Biogeography of Compositae, Funk, V.A., A. Susanna, T. Stuessy, and R. Bayer (eds.). IAPT, Vienna, Austria.Google Scholar
- Chissoe, W. F. & J. J. Skvarla. 1974. Sucrose density pads for concentration and purification of pollen grains. Stain Tech. 49: 123–124.Google Scholar
- ——— & ———. 1996. Combining sputter coating with OTOTO treatment to eliminate charging artefacts in pollen preparations. Oklahoma Acad. Sci. 76: 83–85.Google Scholar
- Erdtman, G. 1960. The acetolysis method. A revised description. Svensk Botanisk Tidskrift 54: 561–564.Google Scholar
- Funk, V. A. & R. Chan. 2008. Phylogeny of the Spiny African Daisies (Compositae, tribe Arctotideae, subtribe Gorteriinae) based on trnL-F, ndhF, and ITS sequence data. Mol. Phylogenet. Evol. 48: 47–60.Google Scholar
- ———, R. J. Bayer, S. Keeley, R. Chan, L. Watson, B. Gemeinholzer, E. Schilling, J. A. Panero, B. G. Baldwin, N. Garcia-Jacas, A. Susanna & R. K. Jansen. 2005. Everywhere but Antarctica: using a supertree to understand the diversity and distribution of the Compositae. Biol. Skr. 55: 343–374.Google Scholar
- Karis, P. O. 2006. Morphological data indicates two major clades of the subtribe Gorteriinae (Asteraceae–Arctotideae). Cladistics 22: 199–221.Google Scholar
- Maddison, D. R. & W. P. Maddison. 2005. MacClade 4: Analysis of Phylogeny and Character Evolution, version 4.07. Sinauer, Sunderland.Google Scholar
- McKenzie, R. J., J. Samuel, E. M. Muller, A. K. W. Skinner & N. P. Barker. 2005. Morphology of cypselae in subtribe Arctotidinae (Compositae–Arctotideae) and its taxonomic implications. Ann. Missouri Bot. Gard. 92: 569–594.Google Scholar
- Panero, J. L. & V. A. Funk. 2002. Toward a phylogenetic subfamilial classification for the Compositae (Asteraceae). Proc. Biol. Soc. Washington 115: 909–922.Google Scholar
- Punt, W., S. Blackmore, S. Nilsson & A. Le Thomas. 1994. Glossary of pollen and spore terminology. LPP Contributions Series. LPP Foundation, Utrecht.Google Scholar
- Roessler, H. 1959. Revision der Arctotideae–Gorteriinae (Compositae). Mitt. Bot. Staatssamml. München 3: 71–500.Google Scholar
- ———, ———, V. C. Patel & A. S. Tomb. 1977. Pollen morphology in the Compositae and in morphologically related families. Pp. 141–248 in V. H. Heywood, J. B. Harborne & B. L. Turner (eds.), The Biology and Chemistry of the Compositae. Academic Press, London.Google Scholar
- Turner, B. L. 1977. Summary of the biology of the Compositae. Pp. 1105–1118 in V. H. Heywood, J. B. Harborne, & B. L. Turner (eds.), The Biology and Chemistry of the Compositae. Academic Press, London.Google Scholar
- Ueno, J. 1972. The fine structure of pollen surface III: Gazania and Stokesia. Reports of Faculty of Science, Shizuoka University 7: 103–116.Google Scholar
- Wortley, A. H., V. A. Funk, H. Robinson, J. J. Skvarla & S. Blackmore. 2007. A search for pollen morphological synapomorphies to classify rogue genera in Compositae (Asteraceae). Rev. Pal. & Pal. Early availability online (doi: 10.1016/j.revpalbo.2007.03.003).