Thesium hirtum (Sond.) Zhigila, Verboom & Muasya, 2019

Zhigila, D. A., Verboom, G. A., Stirton, C. H. & Muasya, A. M., 2019, A taxonomic revision of Thesium section Hagnothesium (Santalaceae) and description of a new species, T. quartzicolum *, South African Journal of Botany 124, pp. 280-303 : 296-299

5.2.2.3. Thesium hirtum (Sond.) Zhigila, Verboom & Muasya comb. nov.

Basionym: Thesidium hirtum Sond. in Flora 40: 364 (1857a).

Thesium strigulosum A.DC in DC. Prodr. 14: 673 (1857a).

Thesidium strigulosum (A. DC.) A.DC. based on female plants (in DC. Prodr. 14: 673 (1857b).

Type: South Africa, Western Cape, Cape Town (3318): Table Mountain , near Constantia (-BD), without precise date, ♂ & ♀ plants, Ecklon & Zeyher 35 ( M, BOL, S syntypes).

Thesium globosum A.DC. in Esp. Nouv. Thesium 4: (1857a). Thesidium globosum (A.DC.) A.DC. based on male plants in DC. Prodr. 14: 673 (1857b).

Type: South Africa, Western Cape, Cape Division, Table Mountain Nature Reserve (3418CD), Constantia neck, ♂ & ♀ plants, Bolus 4689 (BOL, lectotype! designated here; K!, PRE! isolectotypes). We chose this lectotype as it contains both male and female plants and is cited by Hill (1925) as one of the syntypes.

An erect heath-like perennial suffrutex, 10– 5 cm tall, yellowish green in appearance, plant not brittle, taproot stout, branches arise mainly at basal portion, 3–12 branches, branching pattern fastigiate, leaves subtending branchlets. Stems woody at base, herbaceous above, 1–3.0 mm in diameter, erect or suberect, scabrous, conspicuously sulcate in transverse section, with hispid structures at edges. Leaves well developed, incurved with tips adpressed to the stem, green at basal portion but turn yellowish toward the attenuate tips, tomentum scabrid, raised midrib with short hispid protrusions, leaf apex acute, margins ciliate sharp-edged, mostly straight, seldom concave. In fl orescences arranged in axils of branchlets along the branch length in short solitary or dense spikes, sessile or attached to the stem by a short pedicel; bracts and bracteoles leaf-like; bracts thick, 2–4 × 1.5–3 mm, ovate to lanceolate, conspicuously scabridulous on transparent margins, yellowish-green, acute at tips, relatively longer than the flower length, usually curved; floral bracteoles bract-like but smaller, 2–3 × 0.5–2.5 mm; flowers campanulate, yellowish green, 1–2 × 1–1.8 mm, 4-merous, external gland between perianth lobes absent, perianth lobe segments 0.5–1.5 × 0.5–1 mm, lobes ovate to lanceolate, obtuse or subacute at tips, neither distinctly uncinate nor lobulate; lobe tube short, about 0.2 mm. Male and female plants well differentiated. Male plant: branches more slender than in female plants, internodes short, 0.7–1.6 mm long; leaves dense, closely imbricate, male leaves as thick as female leaves, lanceolate, 2–3 × 0.5–1.5 mm; inflorescences lax; hypanthium tube short to non-existent, stamen tetramerous, staminal filaments attached to the walls of perianth lobe at base of tube, about 2.5 mm, leaves dense, imbricate, linear to linear-lanceolate, 2.4–6 × 0.5–1.5 mm. Female plant: branches more woody than in male plants, internodes short, 0.7–1.5 mm long as in female counterpart; leaves dense, imbricate, linear-lanceolate, 6–12 × 0.5–2 mm; inflorescences lax; hypanthium tube shorter than the perianth lobe tubes but more elongated than in male plants; style stout, 0.2–0.6 mm. Fruit a nutlet, ovoid, pale green, elaiosome absent, 2–3 × 2–2.5 mm, with 10 conspicuous ribs, with reticulate venation in between ribs, capped with orange to golden green persistent perianth segments that are shorter relative to fruit length ( Fig. 12 ).

5.2.2.3.1. Diagnostic features. T. hirtum is similar to T. fruticulosum in its growth form, linear to lanceolate leaves, leaf-like bracts and bracteoles that are longer than flowers, inflorescences in bract axils subtended by tufts of bracteoles and ovoid fruits. Thesium hirtum is readily distinguished by its hirsute structures on the entire plant surface (versus glabrous), conspicuously keeled leaves, leaf margins erose and ciliate along the ridges of the midrib and leaf margin (versus leaves not keeled, midrib almost absent or subterete, without prominent ridges in T. fruticulosum ).

5.2.2.3.2. Distribution and habitat. Thesium hirtum is widespread across the lower slopes of the entire coastal mountain ranges of the West Coast Peninsula to Cape Peninsula to Potberg in the De Hoop Nature Reserve and toward the Groot Swartberg Nature Reserve in the Western Cape ( Fig. 7E , solid circles). It has been collected in coastal fynbos, on sandstone mountain fynbos but rarely on quartz or limestone hills between sea level and c. 1300 m a.s.l.

5.2.2.3.3. Conservation status. Thesium hirtum has been designated LC (Least Concerned) status ( Raimondo et al., 2009; Von Staden, 2015) as species are found in Nature Reserves across its range. Our assessment supports this status. However, with current stochastic events of recurrent fires in Western Cape, plant populations with poor post-fire regeneration such as T. hirtum might be negatively impacted and threatened ( Bond and van Wilgen, 1996), and need to be monitored.

5.2.2.3.4. Additional specimens studied. South Africa. WESTERN CAPE. 3218 (Clanwilliam): Lokenburg ; 21 mi S of Nieuwoudtville (- CA) , 25 Aug 1958, ♂ & ♀ plants, Story 4348 ( PRE) . 3318 (Cape Town): Table Mountain (- AB) , Sep 1963, ♀ plants, Stauffer 5141 ( PRE) ; Wynberg hills, (- AB) , 28 Aug 1963, ♀ plants, Staufer 5053 ( BOL) . 3321 (Ladismith): Berfontein, west hills of Witteberg , above Witelsrivier, Langeberg (- DC) , 12 Nov 1931, ♀ plants, Compton 3852 ( BOL) . 3322 (Oudtshoorn): near Robinson (- DC) , 26 Sep 1991, ♂ & ♀ plants, Leighton 3157 ( BOL) . 3323 (Willowmore): Donkerhoek se Nek , Prince Alfred's Pass (- DD) , 16 Feb 1964, ♂ & ♀ plants, Levyns 11508 ( BOL) . 3418 (Simonstown): near Rainfall Exclusion Experiment Plots, Kalk Bay ridge, Steenberg (- AB) , 10 Oct 2009, ♀ plants, Moore 177 ( BOL) ; Simons Bay, near Simons Town (- AC) , ♂ & ♀ plants, Zeyher 3815 ( K, S) ; Hills near Simon's Town (- CA) , 30 Jun 1918, ♂ & ♀ plants, Bolus 3939 ( BOL) ; Constantia neck, Table Mountain Nature Reserve (- CD) , 01 Jan 1879, ♂ & ♀ plants, Bolus 4689 ( BOL) ; Smith's farm , Cape Point , (- BD) , 16 Jan 1936, ♂ & ♀ plants, Compton 6047 ( NBG) ; Table Mountain, near Constantia neck (- BD) , without precise date, ♂ & ♀ plants, Ecklon & Zeyher 35 ( BOL) ; Silvermine (- AC) , 04 Apr 2017, ♀ plants, Zhigila 114 ( BOL) ; N slopes, Constantiaberg (- AB) , 29 Aug 1963, ♂ & ♀ plants, Stauffer 5070 ( BOL, PRE) . 3419 (Caledon): Elim (- CD) , 20 May 1996, ♀ plants, Schlechter 7642 ( BOL26299 ) ; hills in Rietfontein area, Elim , 01 Dec 1928, ♂ plants, Bolus 318/4 ( BOL) ; Zwartberg , 09 Dec 1896, Bolus 8602 ( BOL) . 3420 (Bredasdorp): Montibus, Koude River (- DA) , 04 Dec 1896, ♂ & ♀ plants, Schlechter 9627 ( PRE) ; near Elim (- AD) , 04 Dec 1898, ♂ & ♀ plants, Schlechter 9628 ( BOL) ; Limestone Hills, Pearly Beach (- AC) , Without precise date, ♀ plants, Esterhuysen 32996 ( BOL) ; Upper flats above Boskloof, Potberg Mountain (- BC) , 18 Aug 1980, ♂ plants, Burgers 2440 ( NBG, STE) .

Figures

Fig.12. Thesium microcarpum:(A) a viewof male plant displaying slender rootstock,(B) closerview of slenderrootstock,(C)habit andsubstrate of sprawling male plants,(D) detailedview of male plant, (E) female fruiting shoot, (F) dense branchlets with dense flowers in male plants. Photographs: Daniel Zhigila.

Fig. 7. Distribution of species of Thesium section Hagnothesium: (A) T.fragile, (B) T.fruticulosum, (C) T.microcarpum, (D) T.minus, (E).T.hirtum •, T.quartzicolum ▲, (F) T.leptostachyum •, T. longicaule ▲.