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On the giant plant genus Cyperus (Cyperaceae): convergent evolution, rapid radiations and generic reclassification

Book Contribution - Book Abstract Conference Contribution

Linneaus (1753) placed Cyperaceae with flattened spikelets and distichous glumes into Cyperus. This morphology has since been shown to have independently evolved in other genera, while reversal to spiral glumes has occurred in multiple lineages within Cyperus. There has been disagreement over whether to recognize Cyperus as a single genus (c. 1000 species) or to segregate it into 14 genera. Segregate genera have been delimited on a single or a combination of characters, but molecular data have demonstrated convergent evolution in key characters. Using molecular data, we reconstructed a phylogeny of Cyperus. The ancestor of Cyperus is a perennial with C3 photosynthesis, and spikelets with distichous glumes which shed individual fruits. Three segregate genera, differing by having spiral glumes (Kyllingiella, Oxycaryum) or spikelets dispersing as a single unit (Courtoisina), are derived from the C3 ancestral morphology and were recently merged into Cyperus. A large (c. 700 species) monophyletic clade rapidly radiated from an ancestor, with an anthelate inflorescence and distichous glumes, that switched to C4 photosynthesis in the last 10 mya. Diversification has been accompanied by reductions leading to spikelets bearing single flowers (Alinula, Ascolepis, Lipocarpha, Volkiella), multiple origins of lateral nutlet orientation (Kyllinga, Pycreus, Queenslandiella), and evolution of sterile lower flowers (Remirea, Sphaerocyperus). To resolve the paraphyly of Cyperus and provide a classification reflecting evolution, we are revising generic delimitation, to recognize a single large genus and delimit infrageneric taxa for clades supported by morphology. Some of these infrageneric groupings are similar to previous classification by K√ľkenthal (1935-36).
Book: Southern African Society for Systematic Biology, 10 Meeting, Abstracts
Number of pages: 1
Publication year:2012
Accessibility:Closed