Classification
Higher Taxonomy
Order - Poales
The Cyperaceae is currently placed in the order Poales. This order, as defined in APG III (Stephens, 2001 onwards), contains 16 families, however, phylogenetic evidence is not consistent. Therefore, further clarification of both the delineation of some families and the boundary of the order itself is needed. This order contains five notable families Cyperaceae, Poaceae, Juncaceae, Typhaceae and Bromeliaceae.
Family - Cyperaceae
APG III recognises two sub-families, Mapanoideae and Cyperoideae, as sister groups in Cyperaceae. Recent molecular phylogenetics strongly supports these clades (Muasya et al.., 2009), however, earlier morphological studies differ in the number and delineation of sub-families (Bruhl, 1995, Ghoetghebeur, 1998).
Genus - Cyperus
Within the genus Cyperus there is no fully accepted classification, rather, there have been a number of attempts, historically, to subdivide it, which are complex and conflicting.
Kükenthal (1935) accepts subgenus Eucyperus (Griseb.) Clarke where he places C. papyrus. This is one of six subgenera he recognised in Cyperus, with subgg. Juncellus, Pycreus, Mariscus, Kyllinga and Torulinium, all six have been recognised as separate genera in narrower circumscriptions of Cyperus. Eucyperus was first recognised at subgeneric level, C. subg. Eucyperus Griseb., based on the absence of C4 related (eucyperoid) anatomy, i.e. Kranz syndrome., compared to C. subg. Chlorocyperus Schischkin in which it is present, later Rikli (1895, not seen) treated these taxa as separate genera, (Goetghebeur, 1989). However, C. papyrus is part of a clade in which C4 chemistry and, therefore, the attendant Kranz syndrome is present, and this highlights the problematic nature of this subgeneric delineation.
An alternative generic subdivision is based upon inflorescence morphological characters. Subgenus Pycnostachys C.B. Clarke, with reduced rachis’ and therefore digitate (congested inflorescence) heads of spikelets and the subgenus Choristachys C.B. Clarke which has elongated rachis’ with spreading spikelets (open inflorescence). Kükenthal also recognises this arrangement, not as implied by Goetghebeur (1989) at subgenus level, rather as two “Parts” circumscribing subgenus Eucyperus, Kükenthal (1935: 42). C. papyrus he places in Choristachys, the group with open inflorescences. N.B. however, there is sufficient variation even intraspecifically in C. papyrus to represent both arrangements, c.f. specimens S33 and S37 compared to S18 and others.
Goetghebeur (1989) postulated that chlorocyperoid anatomy, C4chemistry, was unlikely to have arisen more than once in Cyperus and therefore that this character set should form the basis of an intrageneric classification, using the subgg. names Anosporum (Nees) C.B. Clarke for those species with eucyperoid anatomy and Cyperus for those with chlorocyperoid.
Kükenthal (1935) also defined numerous sections, placing C. papyrus in section Papyrus. The characters he used were several, including the shape of the spike, presence or absence of rachilla wings and their margin colour,, presence of absence of stem leaves, length of the style etc. These sections stand in need of revision, Larridon et al., 2011.
The currently accepted view is of Cyperus in a tribe Cypereae considered to comprise two clades well supported by morphology, including embryology, and molecular studies, Ficinia with 155 species, and Cyperus with about 696 Huygh et al. 2010. The genus Cyperus is considered paraphyletic, containing 13 segregate genera, which have previously been to various ranks, and are, therefore, partly the cause of much of the confused nomenclature and taxonomy leading to the publication of more than 350 infrageneric sub‑divisional names, Reynders et al.. 2011, without sufficient molecular evidence to arrive at a resolution.