Schoenus inconspicuus T.L.Elliott, Euston-Brown & Muasya, 2020

Elliott, Tammy Lynn, Euston-Brown, Doug I. W. & Muasya, A. Muthama, 2020, Schoenus inconspicuus (Cyperaceae, tribe Schoeneae): a new species from Southern Africa, Phytotaxa 440 (3), pp. 239-244 : 240-243

Schoenus inconspicuus T.L.Elliott, Euston-Brown & Muasya , sp. nov ( Figs. 1 , 2 , and 3).

Long, linear-lanceolate spikelets. Glumes relatively long and chartaceous, often shredding with age.

Type:— SOUTH AFRICA. Western Cape: Lower Tokai Park , near N. end, S 34°3’10’’ E 18°26’4’’, 14 m, 17 November 2019, Elliott & Euston-Brown TE 2016_439 A (holotype BOL!; isotype MT!) .

Note: Variation in the wild might be wider that what is described here, as measurements were made from two specimens. These specimens were the only ones with the pertinent characters, such as mature spikelets, in a measurable state.

Caespitose, phyllopodic perennial graminoid. Culms terete, 265–506(‒555) × 0.7–1.0 mm. Leaves basal, 1–3, (69–)89–160 × 0.3‒0.6 mm, about half the length of the culm or less, usually partially curled, proximally channelled, margin serrate above sheath. Sheaths firm, reddish-brown, longitudinally striate. Ligule varying from short and firm to longer and chartaceous, 0.5‒1.4(‒2.4) mm long. Inflorescence a long, narrow pseudolateral panicle, (45–)51‒96(‒100) × 4‒6 mm, proximal rachis 17‒37 mm long. Proximal primary inflorescence bracts apex acute to acuminate, not widened at base, 57‒69 mm long, exceeding length of inflorescence, longitudinal veins not notable, readily breaking-off. Proximal and subproximal primary inflorescence bracts without membranaceous extensions at base. Spikes 3, (12.0–)16.0‒33.8(‒43.0) mm long, dispersed along rachis. Spikelets linear-lanceolate, relatively long, 6.6‒8.2 × 1.0‒ 1.4 mm, pedicellate, 3–6 spikelets per spike. Proximal spikelet prophyll 1 per spikelet, with vein extending to mucro, (0.8–)1.4‒2.4(‒4.6) mm long, prophyll mucro (0–)0.6‒1.6(‒4.2) mm long. Rachilla varying in length, (1.6–)3.8‒6.0(‒11.6) mm long. Glumes 4‒6 per spikelet, proximal glume (1.6–)2.4‒5.8(‒9.1) mm long, subproximal glume 4.2‒6.6(‒7.8) mm long, upper glumes longer than basal ones, lower glumes usually over half the length of spikelet, often shredding with time, usually charteacous in texture. Glume mucros sometimes absent, proximal glume mucro (0–)0.1‒0.3(‒1.7) mm long, subproximal glume mucro 0.1‒1.2(‒2.9) mm long. Stamens 3 per floret, anthers not measured. Stigmas 3-branched (1 observed), vestigial stigmas of second bisexual floret not observed. Perianth bristles not observed. Nutlet narrow elliptic, trigonous, yellowish in colour, 2.2‒3.9(‒4.6) × 0.8‒1.0 mm. Nutlet beak 0.6 mm long (one measured), hispid. ( Figs. 1 and 2 ).

Distribution and ecology: — Schoenus inconspicuus has been collected from acid sand flats (a rare habitat in South Africa) between 14 and 250 m in elevation on the Cape Peninsula and western Agulhas Plain region of South Africa ( Fig. 3 ). This species appears to be rare and localized, having first been collected in 1919 on Bergvliet Farm by William Purcell (Purcell 592)—an area that has since become a residential suburb. The Levyns’ collection in 1938 on Rooihoogte is within the Cape of Good Hope National Park, a site where the habitat has been conserved. However, several recent searches for this population have been unsuccessful. Recently discovered populations in Tokai and the Agulhas Plain are limited to a few individuals; thus, the currently known total population size of S. inconspicuus is less than 10 individuals in two small areas.

Phenology —Flowering May and November (one specimen observed for each month), fruiting June (one specimen observed).

Etymology —The specific epithet “ inconspicuus ” refers to the fact that this species is not easily noticeable once it sheds its seeds, and thus it is easily overlooked.

Taxonomic note: —The relatively long, linear-lanceolate spikelets of S. inconspicuus are most similar to those of S. ligulatus (see Elliott et al. 2019); however, spikelet length, glume texture and relative length, mucro length and habitat preferences differ between the two species ( Fig. 2 ). Spikelets in S. inconspicuus are longer (> 6.6 mm), whereas they are generally less than 5.7 mm in S. ligulatus (Elliott et al. 2019) . Compared to the glumes of S. ligulatus , those of S. inconspicuus are more chartaceous in texture appearing silvery-white when young in some specimens. These ‘papery’ glumes then shred as they deteriorate with age. In addition, the lower glumes of S. inconspicuus are relatively long and often over half to three quarters of the spikelet length, differing from those of S. ligulatus , which are usually less than half of the length of the spikelet. The glume mucros also differ between the two species, with S. ligulatus having more prominent aristate lower glumes, whereas the glume mucros of S. inconspicuus are often poorly formed or lacking. Habitat preference, however, is the most important difference between the two species, with S. inconspicuus often growing on dry, acid sand, whereas S. ligulatus mostly occurs on wet sites (Elliott et al. 2019).

In its vegetative form, S. inconspicuus seems superficially similar to the grass (family: Poaceae ) Tenaxia stricta (Schrad.) N.P.Barker & H.P. Linder (2010: 352) , which can be a common co-occurring species. A rounded tussock growth form with a tendency to droop and narrow needle-like leaves are shared characters between the two species, especially when plants are not flowering or without old heads. The difference between the two species only becomes obvious after carefully inspecting the base of the plant and in the characteristic leaf sheath feature (closed in Schoenus ; open in Tenaxia ). Another slight difference between the two species is that Tenaxia stricta seems to be lighter green in colour, while S. inconspicuus tends to be darker green but fades to darker brown with age.

Apart from specimens collected within the last eight years, only two other specimens of S. inconspicuus have been found in existing herbarium collections: Purcell 592 and Levyns 6729. These two specimens were found during extensive searches of the BOL, NBG and SAM Cyperaceae collections, with Purcell 592 originally identified as Tetraria cuspidata (Rottb.) C.B.Clarke (in Durand & Schinz (1894): 660) and Levyns 6729 identified as Tetraria variabilis Levyns (1947: 87) —two Tetraria species that have since been transferred into Schoenus ( Elliott & Muasya 2017) . The long, shiny spikelets of both these specimens distinguished them from other Southern African Schoenus specimens.

Conservation status:— We evaluate the conservation status of Schoenus inconspicuus as CRITICALLY ENDANGERED (CR) B2ab(ii,iii,iv), C2ai and D under the IUCN Red List categories and criteria (IUCN 2001) because of its few known populations, small extent of occurrence and the degradation of the habitats surrounding known populations.

Additional specimens examined:— SOUTH AFRICA. Western Cape: Bergvliet Farm, Constantia , small Gethyllis camp, 3418 AB, 14 May 1919, Purcell 592 ( SAM!) ; Lower Tokai Park , near N. end, 3418 AB, 14 m, 17 November 2019, Elliott & Euston-Brown TE 2016_438 ( BOL!) ; Rooihoogte , 3418 AD, 800′, 12 June 1938, Levyns 6729 ( BOL!) ; Groot Hagelkraal , 3419 AD, 54 m, 8 March 2012, Muasya & Chimphango 6479 ( MT!) ; Groot Hagelkraal farm, growing about 5 m from side of vehicle trail, 3419 AD, 58 m, 24 August 2018, Elliott & Muasya TE 2016_370 ( BOL!) ; Groot Hagelkraal , within 5 m from vehicle track near limestone cliffs, 3419 AD, 41 m, 20 November 2019, Elliott & Arens TE 2016_474 ( BOL!) .

Schoenus inconspicuus can be differentiated from similar species in the S. cuspidatus and allies group with linear-lanceolate spikelets as follows (for more details, refer to Elliott et al. 2019, Elliott & Muasya 2020):

1 Culms less than 340 mm in height; spikelets mostly less than 4.5 mm in length ...................................................... Schoenus exilis

- Culms usually greater than 350 mm in height; spikelets 4.5‒8.2 mm in length ................................................................................2

2 Plants mostly occurring on wet sites; spikelets shorter (generally <5.7 mm) and having relatively short, aristate proximal glumes (<2.3 mm); glumes relatively tough (i.e. not completely chartaceous in texture)............................................... Schoenus ligulatus

- Plants occurring on dry, acidic sands; spikelets relatively long (> 6.6 mm) and having relatively long proximal glumes (mostly> 2.4 mm); glumes chartaceous in texture.............................................................................................................. Schoenus inconspicuus

Figures

FIGURE 1. Plant growth form, inflorescence and spikelet morphology of S. inconspicuus. A.—general growth form; B.—pressed specimen; C.—inflorescence; and D.—spikelet. The black scale bar beside the inflorescences in C. represents 10 mm, while the scale bar beside the spikelet in D. represents 1 mm. The photos in A. and B. were taken with a Sony RX100 II camera, whereas the image in C. was taken with a Nikon D90 camera attached to a Nikon AF micro Nikkor 105 mm 1:2:8 macro lens. A Nikon DS-US camera head attached to a Nikon Stereoscopic zoom microscope SMZ1500 was used to take the image in D.

FIGURE 2. Spikelet of S. inconspicuus (A.) compared that of S. ligulatus (B.). The photos were taken with a Nikon DS-US camera head attached to a Nikon Stereoscopic zoom microscope SMZ1500, and the black scale bar represents 1 mm.

FIGURE 3. Documented collection locations of S. inconspicuus. The map was plotted using R 3.5.1 (R Core Development Team 2013).