Festuca drakensbergensis Sylvester, Soreng & M.D.P.V. Sylvester, 2020

Sylvester, Steven P., Soreng, Robert J., Sylvester, Mitsy D. P. V. & Clark, Vincent Ralph, 2020, Festuca drakensbergensis (Poaceae): A common new species in the F. caprina complex from the Drakensberg Mountain Centre of Floristic Endemism, southern Africa, with key and notes on taxa in the complex including the overlooked F. exaristata, PhytoKeys 162, pp. 45-69 : 45

Festuca drakensbergensis Sylvester, Soreng & M.D.P.V. Sylvester sp. nov. Figs 1 , 2 , Table 1

Type.

Lesotho. AfriSki Ski Resort, in valley just west of the resort centre with an east-southeast aspect, 28.824908S, 28.723208E, 3065 m alt., heavily grazed damp Afro-alpine grassland, 28 Feb 2020, S.P. Sylvester, R.J, Soreng & M.D.P.V. Sylvester 3660 (holotype: PRE!; isotypes: NU!, US!).

Diagnosis.

Differs from Festuca caprina s.l. by forming lax short tufts with extravaginally branching tillers and lateral-tending or ascending cataphyllous shoots or lateral-tending rhizomes present, basal foliage reaching < ½ the length of the culms, sheaths of tillers and basal culm (0.5-)2-7(-10) cm long, leaf blades of tillers and basal culm (2-)5-15(-26) cm long, and anthers 0.8-1.6(-1.8) mm long. Differs from Festuca exaristata by its basal sheaths fibrous, leaf blade midrib usually sharp, keel-like, sometimes blunt and rounded, panicle branches pendent, lightly to densely scabrous, lowermost lemma (not including awn) 4.5-5.8 mm long, awn usually present, 0.5-3 mm long, ovary apex sparsely to densely hairy and anthers 0.8-1.6(-1.8) mm long.

Description.

Perennial herbs, generally forming lax, short, isolated tufts, with lateral-tending or ascending cataphyllous shoots or lateral-tending rhizomes present, basal foliage (2-)4-20(-27) cm tall and generally < ½ the length of the culms, with inflorescences largely exerted. Tillers extravaginal, with cataphylls present, intravaginal tillers rarely also present (i.e. Sylvester et al. 3637). Culms (12.5-)20-46(-65) cm tall, 0.3-0.5(-1) mm diam., erect, delicate, cylindrical to slightly compressed, longitudinally striated, glabrous, smooth, with (0) 1 or 2 visible nodes, uppermost node at (1.3-) 3-10(-16) cm from the base, ca. (1/10-)1/8-1/3(- ½) culm height, distance between uppermost node and panicle (3-)14-33(-40) cm long, distance between uppermost node and second node down (0.9-)2.3-6.5(-9.5) cm long, nodes at the base covered by imbricate leaf sheaths. Leaves mostly basal, with 1 or 2 (3) cauline leaves, culm leaves similar to those of the base and tillers; sheaths of tillers and basal culm (0.5-)2-7(-10) cm long, proximally fused ca. ½ their length, implicate above, usually slightly obliquely truncated at the apex, herbaceous, persistent, becoming sparingly fine fibrous - decaying into longitudinal fibres - in the lower portion with age, brownish or yellowish, glabrous, usually smooth, rarely retrorsely scabrous, with 5-7 veins; flag-leaf sheaths 3.4-9.5(-12.5) cm long, fused ca. ½ their length; auricles 0.01-0.2 mm long, inconspicuous, obtuse; ligules 0.1-0.5 mm long, membranous, moderately to strongly decurrent with the sheath margins, truncate, briefly ciliolate; flag-leaf ligules 0.2-0.5 mm long; leaf blades of tillers and basal culm (2-)5-15(-26) cm long, 0.3-0.8(-1) mm wide as rolled or folded, setaceous, erect-curved to recurved, firm to ± rigid, conduplicate, convolute or involute, rarely flat in upper leaves, elliptical or obovate to carinate outline in cross-section, midrib (middle vein) usually sharp, keel-like, sometimes blunt and rounded, abaxial surface glabrous, usually smooth throughout or lightly antrorse-scabridulous towards the apex, adaxial surface scabrous on veins or prickles elongating to become hair-like and appearing shortly hairy, light- to dark-green, apex obtuse (to acute); upper culm leaf-blades similar to those of lower culm and tillers, but shorter and sometimes expanded; flag-leaf blades (0.2-)1.5-4(-12.5) cm long, (2-)15-40(-50)% the length of their flag-leaf sheaths, rarely longer. Panicles 2.5-9(-13) cm long, open to moderately congested, drooping, with (7-)8-20(-50) spikelets often held unilaterally on lower side of axis; central panicle axis smooth to lightly antrorsely scabrid, with 4-10 nodes, usually 1 branch (rarely 2 branches) per node, lowest internode (0.8-)2-4.5(-5.5) cm long, ca. 20-70% length of whole panicle, lowest internode and sometimes upper internodes and panicle branches often sinuous-wavy; panicle branches capillaceous, generally pendent and drooping, lowermost patent to pendent, upper ± appressed to central axis, glabrous, antrorsely scabrous to scaberulous on angles or rarely smooth; lowermost primary panicle branch (1-)1.5-6 cm long, with (1-)3-10(-17) spikelets; pedicels 0.5-3(-6) mm long, shorter than their spikelets, slightly thickened at their apices, glabrous, antrorsely scabrous to scaberulous on angles or rarely smooth. Spikelets (not including awns) (5.5-)6-9(-11.5) mm long, laterally compressed, elliptic, green or usually purplish; florets 2 to 5(6) fertile and usually 1 apical and ± rudimentary, sterile, lowermost fertile floret largest, with upper fertile florets gradually reducing in size; glumes unequal, lower ca. ½ -3/4(-5/6) length and ca. 1/3- ½ width of upper glume, narrowly scarious on the margins, usually darker purple compared to the lemmas, glabrous, keels distally scaberulous for ¼ -1/2 their length or smooth throughout, surfaces smooth throughout or sometimes sparsely scaberulous towards apex, margins usually with scattered hooks on edges in distal ½ (-3/4), (acute or) acuminate; lower glumes 2.1-3(-3.8) mm long, 0.3-0.4 mm wide at base in cross section, reaching to 50-70% length of proximal lemma, linear-lanceolate, 1-veined; upper glumes 3.2-4(-4.9) mm long, 0.5-0.8 mm wide at base in cross section, reaching to 70-95% length of proximal lemma, ovate-lanceolate, 3-veined; rachillas up to ca. 0.8-1.6 mm long, slightly dorsally compressed, glabrous, smooth, lightly scabrous towards apex or densely scabrous throughout; calluses somewhat thick, annulated, angled downward, rugose or smooth, sometimes lightly scabrous; lemmas (lowermost lemma not including awn) 4.5-5.8 mm long, 0.7-1.2 mm wide at broadest point in cross section, ovate-lanceolate, herbaceous with narrowly scarious margins, glabrous, proximally smooth or sparsely to densely scabrous, especially towards the margins, distally sparsely to densely scabrous, especially towards the apex and margins, moderately to densely granulose with clear bead-like raised silica cells appearing like ‘granules’ throughout or these absent towards apex and margins, margins scabrous throughout or in the distal 1/2-3/4, green or usually greenish-purple at the margins and towards the apex, 5-veined, apices acute and tapering into a short awn, sometimes slightly bilobate with awn emerging from between the minute lobes or very rarely muticous, awn 0.5-3 mm long, straight, scabrous; paleas (lowermost) 4.5-5.8 mm long, subequalling to usually equalling the lemma or slightly surpassing the lemma apex by up to 0.4 mm, herbaceous with scarious margins, slightly to deeply bidentate, keels scabrous in distal (1/4-) ½ -5/6 or rarely throughout, between keels smooth, moderately to densely granulose with clear bead-like raised silica cells appearing like ‘granules’, margins scabrous in distal ¼ -1/2. Flowers proximally perfect with uppermost usually sterile; anthers 3 in number, 0.8-1.6(-1.8) mm long, linear, dull yellow; ovaries ca. 0.5-1 mm long, apex sparsely to densely pubescent; lodicules 0.7-0.85 mm long, bilobed with lobes ca. 2-4 mm long, both lobes +/- same size or lateral lobes to 0.2 mm shorter, glabrous, margins entire and smooth or sometimes fimbriate, acute. Caryopses ca. 2.6-3.5 mm long, ca. 1-1.6 mm shorter than lemma and palea, adhering to palea and lemma, narrowly elliptic to slightly narrow-obovate, deeply sulcate, hilum linear, 75-93% length of caryopsis, endosperm hard.

Anatomy-Outline elliptical or obovate to carinate with angled arms, ca. 5 vascular bundles all positioned in the centre of the blade and at the same level, ca. 4 grooves, ca. 5 ribs; the central rib is located in the central area of the blade. Abaxial> surface with straight edges forming angles associated with the vascular bundles, ribs angular, composed of sclerenchyma block and found opposite all vascular bundles, smooth, macro-hairs absent, margins composed of sclerenchyma block. Adaxial surface markedly irregular, with rounded ribs situated opposite all vascular bundles, lacking sclerenchyma block, prickles present and densely covering the entire surface, sometimes more prevalent on the ribs, usually extending and appearing hispid (Fig. 2E, F ).

Distribution and habitat.

Endemic to the high-elevation DMC of South Africa and Lesotho ( Carbutt 2019). In South Africa, the species is known from the Eastern Cape and KwaZulu-Natal Provinces, with it also possibly occurring in the Free State Province, although no specimens have as yet been verified. Festuca drakensbergensis is a common constituent of both moderately grazed and little disturbed Afro-alpine vegetation (viz. Carbutt’s 2015 'austro-alpine region’), and less often in Afro-montane vegetation, of the DMC, ca. 2150-3270+ m alt. The species is found in grassland, wetland and short Afro-alpine shrubland dominated by species in the genera Chrysocoma L., Erica Tourn. ex L., Eumorphia DC. and Helichrysum Mill. These habitats correspondent with Mucina and Rutherford’s (2006) uKhahlamba Basalt Grassland (Gd 7), Lesotho Highland Basalt Grassland (Gd 8), Drakensberg Afro-alpine Heathland (Gd 10) and Lesotho Mires (AZf 5). Festuca drakensbergensis is rarely dominant and generally occurs in low abundance amongst the larger F. caprina var. macra or amongst other forbs or low shrubs. Of the 222 2 m × 2 m plots studied for all vascular plants across the Afro-alpine DMC (Sylvester et al. unpubl. data), F. drakensbergensis was encountered in usually low abundance (0.5-8[-70]% of overall plot cover) in 35 plots, highlighting its high frequency and ubiquity in these landscapes.

Preliminary conservation status.

The overall extent of occurrence of F. drakensbergensis is relatively large compared to many DMC endemics, perhaps 30% (or 13,000 km2 i.e. above 2150 m) of the total DMC area of ca. 40,000 km2. Given that it is a common species without any specific habitat niche, the total population is likely well above 10,000 mature individuals. However, given the tremendous pressure that the DMC is under from communal rangeland activities - especially in Lesotho ( Global Mechanism of the UNCCD 2018, 2019) - it is possibly at medium- to long-term risk from land degradation through overgrazing. Initial observations suggest that the species does have resilience, being recorded in areas disturbed by grazing and burning as well as in areas of limited disturbance. There might, however, be competition from shrubland following overgrazing (e.g. Chrysocoma ciliata L., Selago melliodora Hilliard, Eumorphia spp. and Helichrysum spp.). Future projections of global climate change are also of concern for high-elevation species in southern Africa ( Bentley et al. 2019). Accordingly, we propose the IUCN conservation status of Near Threatened (NT) until further population studies can be undertaken.

Etymology.

The species epithet refers to the Drakensberg Mountain Centre (DMC) of South Africa and Lesotho ( Carbutt 2019), where this species forms a common component of the Afro-alpine vegetation.

Notes.

The character of extravaginal branching is not always easy to distinguish and certain specimens of F. caprina s.l. found growing in moss may have what appear to be rhizomes although these are, in fact, pseudostolons. However, F. caprina var. caprina and var. macra plants are usually much larger, with culms (28-)35-120+ cm tall, basal foliage (10-)30-80+ cm tall, generally (> ½)> ¾ to surpassing the length of the culms, with leaf-blades of tillers and basal culm (4-)12-66.5+ cm long, often> 26 cm long, basal sheaths entire, erect panicles with greenish or purplish spikelets on ascending branches, lower lemma often larger, (4.5-)5-7(-9) mm long, and anthers> 2 mm long (vs. culms (12.5-)20-46(-65) cm tall, basal foliage (2-)4-20(-27) cm tall, leaf-blades of tillers and basal culm (2-)5-15(-26) cm long, basal sheaths fibrous, drooping panicles with purplish spikelets on pendent branches, lower lemma 4.5-5.8, anthers 0.8-1.6(-1.8) mm long in F. drakensbergensis ) (Table 1 ). Festuca caprina var. irrasa specimens can sometimes superficially resemble F. drakensbergensis by having shorter basal foliage reaching < ½ length of the culms, with smooth blades and fibrous basal sheaths (Table 1 ). However, in these cases, F. caprina var. irrasa can be distinguished by its intravaginally branched tillers which lack cataphylls, erect panicles with ascending branches, short-hispid or long-scabrous lemmas and paleas that often measure> 6 mm long, and anthers> 2 mm long (vs. extravaginally branched tillers with cataphylls present, drooping panicles with pendent branches, lemmas and paleas glabrous, scabrous, 4.5-5.8 mm long, and anthers <1.8 mm long in F. drakensbergensis ).

Festuca exaristata also bears extravaginally branched cataphyllous tillers or lateral-tending rhizomes, with plants forming short isolated tufts. The holotype of F. exaristata is very short, with basal foliage not reaching past 12 cm tall, and bears superficial resemblance to certain shorter specimens of F. drakensbergensis , for example, Sylvester et al. 3637. The protologue of F. exaristata mentions culms to 35 cm tall and leaf blades to 25 cm long, which must refer to the one paratype, du Toit 2713 (K), which has not been seen by us, showing that the species would also superficially match larger versions of F. drakensbergensis . However, F. exaristata differs by its entire, lustrous basal sheaths, blunt, rounded leaf-blade midribs, erect sub-spike-like panicles, smooth panicle branches, shorter lemmas 4-4.2 mm long which lack awns, glabrous ovary apex and anthers 1.5-1.8 mm long (vs. basal sheaths smooth or rarely retrorsely scabrous, fibrous, leaf blade midrib usually sharp, keel-like, sometimes blunt and rounded, panicles drooping, panicle branches lightly to densely scabrous, lowermost lemma (not including awn) 4.6-6 mm long, awn rarely absent, usually 0.5-3 mm long, ovary apex sparsely to densely hairy, anthers 0.8-1.6(-1.8) mm long in F. drakensbergensis ). Although rarely some characters overlap between F. drakensbergensis and F. exaristata , the combination of characters found in F. exaristata is never found in specimens of F. drakensbergensis .

Some specimens (e.g. Sylvester et al. 3442) growing in wetlands with limited grazing were substantially larger than normal, with culms to 65 cm tall and inflorescences to 13 cm long.

Selected specimens examined.

Lesotho. Bokong Nature Reserve, ca. 350 m north from the information centre, 29.067203S, 28.421496E, 2972 m alt., Afro-alpine grassland dominated by Lachnagrostis barbuligera var. barbuligera with moderately controlled grazing and burning, 2 Mar 2020, S.P. Sylvester et al. 3687a (US); Bokong Nature Reserve, ca. 400 m north from the information centre, 29.065893S, 28.420137E, 2979 m alt., rocky Afro-alpine grassland dominated by Lachnagrostis barbuligera var. barbuligera with moderately-controlled grazing and burning, 2 Mar 2020, S.P. Sylvester et al. 3689 (PRE, US); Matebeng Pass, below highest summit close to the pass, 29.870708S, 28.976534E, 3094 m alt., "Lesotho Highland Basalt Grassland" with clear elements of "Drakensberg Afro-alpine Heathland" with Erica and Helichrysum shrubs dominating the landscape, 22 Feb 2020, S.P. Sylvester et al. 3578 (PRE, US); Menoaneng Pass, on road between Rafolatsane and Thaba-Tseka, 29.427423S, 28.951273E, 3040 m alt., Afro-alpine grassland, windy ridge, grazed down to low turf, 24 Feb 2020, S.P. Sylvester et al. 3595 (NU, PRE, US); Menoaneng Pass, on road between Rafolatsane and Thaba-Tseka, 29.427403S, 28.951124E, 3039 m alt., Afro-alpine grassland, windy ridge, grazed down to low turf, 24 Feb 2020, S.P. Sylvester et al. 3605 (PRE, US); Sani Pass area, close to the top of the Pass northwest of Sani Mountain Lodge, 29.521251S, 29.200602E, 3242 m alt., short Afro-alpine grassland, close to a pool of water, frequently to heavily grazed, 26 Feb 2020, S.P. Sylvester et al. 3636 (PRE, US); Sehlabathebe National Park, lower end of the Park on the border, 29.860061S, 29.095497E, 2719 m alt., damp Afro-alpine tussock grassland, soil damp, under dripping crag, heavily grazed, close to livestock paths, 19 Feb 2020, S.P. Sylvester et al. 3531 (NU, PRE, US). South Africa. Eastern Cape: Bastervoetpad Pass area, ca. 12 km east of Mountain Shadow Hotel on Barclay Pass, 31.176139S, 27.964197E, 2176 m alt., Afro-montane transitioning to Afro-alpine grassland, 14 Feb 2020, S.P. Sylvester et al. 3505 (NU, PRE, US); Eastern Cape: between Carlisleshoekspruit Pass and Tiffindell Ski Area, 30.677202S, 27.956643E, 2526 m alt., riparian wetland, 10 Feb 2020, S.P. Sylvester et al. 3442 (NU, PRE, US); Eastern Cape: Tiffindell Ski Area, Ben Macdhui summit, 30.647683S, 27.934042E, 2995 m alt., Afro-alpine grassland, 11 Feb 2020, S.P. Sylvester et al. 3459 (NU, PRE, US); KwaZulu-Natal: Drakensberg, top of Sani Pass, grassy slopes on bank of gully, steep east facing slope, between rocks in brown clayey soil, 9400 ft [2865 m alt.], 24 Mar 1975, P.C.V. du Toit 698 (PRE0240733); KwaZulu-Natal: Sentinel Trail, ca. 1.2 km from the chain ladders, 28.740834S, 28.886806E, 2867 m alt., Afro-montane grassland grading into Afro-alpine grassland, damp soil, infrequently grazed, 6 Mar 2020, S.P. Sylvester et al. 3714 (NU, PRE, US); KwaZulu-Natal: Sani Pass area, below southwest facing cliffs to the southeast of Sani Mountain Lodge, 29.585365S, 29.290839E, 2866 m alt., short Afro-alpine grassland, frequently to heavily grazed, 26 Feb 2020, S.P. Sylvester et al. 3637 (PRE, US); [KwaZulu-Natal?:] Probably from Mont-aux-Sources [Sentinel Peak?], E.A.C.L.E. Schelpe 1394A (PRE0024522).

Figures

Figure 1. Festuca drakensbergensis, habit and inflorescence characteristics. A, B Whole plant C spikelet, lateral view D [from left to right] palea ventral view showing ovary, lemma dorsal view, upper glume dorsal view, lower glume lateral view E ovary apex, ventral view F caryopsis, dorsal view, with parts of torn palea and lemma at base. A, C, D, F of isotype S. P. Sylvester et al. 3660 (US) B of S. P. Sylvester et al. 3578 (US) E of S. P. Sylvester et al. 3687 a (PRE).

Figure 2. Festuca drakensbergensis, leaf morphological and anatomical characteristics. A Junction of tiller sheath and blade, lateral view B ligule of tiller, ventral view C abaxial tiller blade surface, showing keel D adaxial tiller blade surface E, F tiller blade cross sections, showing position of the sclerenchyma block (scl), vascular bundles (vb) and scabers (sca) on the adaxial surface. A, B, C, E of isotype S. P. Sylvester et al. 3660 (US) D of S. P. Sylvester et al. 3689 (PRE) F of isotype S. P. Sylvester et al. 3660 (US) drawn by M. D. P. V. Sylvester.