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 phylogenetic studies strongly support 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 (1936) accepts subgenus Eucyperus (Griseb.) C.B. 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 heads of spikelets (congested inflorescence) 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 (1936: 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 (1936) 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 genus Cyperus was considered by several authors to be paraphyletic and likely to comprise 13 segregate, recognisable genera, which have been described at various taxonomic ranks. More than 350 infrageneric sub‑divisional names have been published for Cyperus, leading to much confused nomenclature and taxonomy, with insufficient molecular evidence to arrive at a clear resolution (Reynders et al., 2011).
Reynders et al. (2010) recommended to abstain from a classification of genera in Cypereae, pending further molecular resolution of generic delineations. The resolution of Cyperus generic limits sought by Reynders et al. is provided for the chlorocyperoid subgenus by recent molecular evidence, which indicates that nine previously postulated segregate genera form nested, generally monophyletic, clades, and, therefore, recommends rejection of the paraphyletic view in favour of a broadly delineated Cyperus (Larridon et al., 2013). This work is likely to underpin future reviews of the sections and series of subgenus Cyperus (Larridon et al., 2013, Larridon et al., 2011a).
However, pending such a review, Cyperus papyrus is currently placed in section Papyrus (Willd.) Thouars, as delimited by Kükenthal. Sectional characters for section Papyrus include decurrent, lanceolate rhachilla-wings which detach from the glumes, styles long, numerous cylindrical spikes, sub-erect and sub-terete spikelets, stem leaves sheathing only, and others.
Cyperus
Cyperus; Cyperus papyrus
Cyperus; Cyperus papyrus