Tetraria cuspidata (Rottb.) C.B.Clarke

Elliott, T. L. & Muasya, A. M., 2017, Taxonomic realignment in the southern African Tetraria (Cyperaceae, tribe Schoeneae; Schoenus clade) *, South African Journal of Botany 112, pp. 354-360 : 358

6.4. Tetraria cuspidata (Rottb.) C.B.Clarke and allies

Originally described by C.F. RottbØll in 1773 as Schoenus cuspidatus , this species ( Fig. 2D, I ) has the most number of accessions and greatest extent of the southern African Tetraria from the Schoenus clade ( Fig. 3d ; Copenhagen: Global Biodiversity Information Facility, 2014). RottbØll summarized the species as having terete, partially nude culms with thin, linear panicles and spirally arranged, oblique glumes terminated by long awns ( RottbØll, 1773). He also included a series of drawings in addition to circumscribing the species, however, no location or reference specimens were given ( RottbØll, 1773). Similarly, the holotype of S. cuspidatus is without locality, collector name or collection data (#C10010615—Museum Botanicum Hauniense, University of Copenhagen).

Clarke provided a more detailed description of the species, after transferring it into the genus Tetraria ( Durand and Schinz, 1894; Clarke, 1900a). Clarke's circumscription of the species included specimens ranging from the western coast of South Africa to the east coast near East London ( Clarke, 1900a). Levyns (1947) followed by emending the circumscription of T. cuspidata and describing several similar species found on the Cape Peninsula of South Africa, while noting the difficulties in discriminating among taxa in this group. Our preliminary examination of T. cuspidata specimens from six herbaria (BOL, BR, GRA, NBG, NU, PRE and WAG; see Thiers, (2017) show that many different morphotypes have been grouped together under this species name, especially for those specimens collected from outside of the region where Levyns focussed her work. It appears that T. autumnalis Levyns , T. compacta Levyns , T. crassa Levyns, T. exilis Levyns , T. graminifolia Levyns T. paludosa Levyns , and Tetraria bolusii C.B.Clarke are distinct taxa closely resembling T. cuspidata , albeit with relatively small geographical extents.

We note that specimens of T. bolusii have often been confused with T. cuspidata , even though the type specimen of T. bolusii has a number of unique characters for this group, including long papery leaf sheaths and relatively short and wide spikelets. Specimens labelled T. cuspidata that have been collected from the Eastern Cape and Natal provinces appear to be unique species, as well as specimens collected from the Cederberg region of the Western Cape province of South Africa. We also predict that there are several other species similar to T. cuspidata that are yet to be described from smaller regions, especially in edaphically heterogeneous areas such as the Agulhas plains.

Also often confused with T. cuspidata , T. sylvatica (Nees) C.B.Clarke was first described as Elynanthus sylvaticus Nees based on a specimen collected by C.L.P. Zeyher from Uitenhage in the Eastern Cape province of South Africa ( Nees von Esenbeck, 1835), with the type currently located at the Muséum National d'Histoire Naturelle in Paris (specimen P00461926). The original circumscription noted terete and striate culms, leaf sheaths with membranaceous edges and short semicylindrical, filiform culm leaves that are channelled above and have scabrous margins ( Nees von Esenbeck, 1835). In addition, the circumscription mentioned that the inflorescences are composed of two or three short and approximate bundles of spikelets, oblong-lanceolate spikelets and have acute, pale margined glumes ( Nees von Esenbeck, 1835). After transferring the species into Tetraria, C.B.Clarke provided a more detailed circumscription and importantly cited specimens from the Western Cape and not the Eastern Cape as in the original circumscription of the species ( Nees von Esenbeck, 1835; Clarke, 1900a).

Tetraria sylvatica is a species with a relatively wide geographical extent – similar to T. cuspidata – but it often prefers lower elevations in the fynbos compared to many other species of Tetraria . Our preliminary examinations of herbarium specimens and recently collected plants from the field suggest that there are several other species closely allied to this group within 150 km of Cape Town. Several specimens also appear to show characters intermediate between T. sylvatica and the T. cuspidata group—a pattern that was previously reported by Levyns (see Adamson and Salter, 1950). We note that the T. sylvatica specimen (Verboom 515) included in the phylogenetic reconstruction of Viljoen et al. (2013) morphologically groups with T. sylvatica var. pseudolorea and does not seem similar to T. cuspidata , explaining why this species appears to be part of the T. compar – T. picta clade in Fig. 1B .

Figures

Fig. 2. Examples of plants from each of the four clades of Schoenus found in southern Africa, showing the corresponding spikelets beneath each plant: A and F—S. nigricans, B and G—T.compar, C and H—Epischoenus sp. and D and I—T.cuspidata.A ‘reticulate-sheathed’ Tetraria of the Tricostularia clade is shown in E, with its spikelet shown in J.The black scale bar beneath the spikelets in F–J represents 1 mm.

Fig. 3. Documented locations of Schoenus nigricans and accepted southern African Tetraria and Epischoenus species in the Schoenus clade of Cyperaceae, based on data downloaded from GBIF (Copenhagen: Global Biodiversity Information Facility, 2014). The following groups of species are included in each map: A, S.nigricans; B, T. compar and allies; C,Epischoenus and allies; and D,T.cuspidata and allies. Schoenus nigricans has a cosmopolitan distribution (A), whereas the distribution of the other three groups is limited to southern Africa (B, C, and D).

Fig. 1. Maximum likelihood phylogenetic reconstruction of the Schoeneae clade of sedges based on ETS,ITS,rbcL,rps16 and trnL-trnF (adapted from Viljoen et al., 2013). The seven major clades of Schoeneae and their approximate divergence times in millions of years are shown in A,with the southern African species highlighted in light grey. Phylogenetic relationships within the Schoenus clade are shown in B, which illustrates the four clades found in southern Africa: S. nigricans, T.compar–T. picta, Epischoenus and T.cuspidata and allies.