Thesium fragile (Forest and Manning, 2013)

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 : 290

5.2.2.1. Thesium fragile L.f. in Supplementarum Plantarum, 162 (1782).

Thesidium fragile Sond. in Flora, 364 (1857a); A.W.Hill in Bull. Misc. Inform. Kew 3: 98 (1915); A.W.Hill in Fl.Cap. 5(2): 202 (1925).

Thesidium podocarpum A. DC. in Esp. Nouv. Thesium : 5 (1857a); A.DC.in Flora, 674 (1857b).

Thesidium thunbergii Sond. in Flora, 364 (1857a).

Type: South Africa, Western Cape, Malmesbury Division, sand dunes at Saldanha Bay, ♂ & ♀ plants, date collected?, Ecklon & Zeyher 29 (K! Lectotype designated here, BOL!, FHO!, NBG!, OXF!, PRE!, Isolectotypes).

Ecklon & Zeyher 29 was selected as lectotype as it was cited in the protologue, deposited at Kew Herbarium together with other earlier collections of Thesium and signed by A.W. Hill who studied the materials in depth.

An erect brittle suffrutex, 10–40 cm tall, heath-like, yellowish to golden green in appearance, with a woody rootstock and simple taproot, scarcely to much-branched, about 4–10 branches, branching pattern virgate, leaves subtending branchlet absent or present, if present at early growth stage. Stems woody at base, herbaceous at distal portion, 2–4 mm in diameter, erect, glabrous, sulcate or subangled in transverse section. Leaves sparingly what? and almost reduced to scales, subrotund, adpressed to the stem, golden to yellowish green, glabrous, no prominent venation or midrib, leaf apex subacute to obtuse, margins entire or cartilaginous, recurved or straight. In fl orescences arranged along the branch length, in axils of branchlets, solitary, sessile to the stem; bracts and bracteoles reduced to scales, bracts fleshy, 0.7–1.5 × 0.5–1.3 mm, broadly triangular, margin slightly fringed with brown, membranous or cartilaginous edges, obtuse at tips, much shorter relative to the flower length, incurved; bracteoles bract-like but smaller, 0.5–1.2 × 0.4–1 mm; flowers campanulate, golden to yellowish green, 0.8–1.8 × 0.7–1.3 mm, 4-merous, rarely 5-merous, external gland absent between perianth lobes, perianth lobe segments 0.5–1.1 × 0.4–0.8 mm, ovate, obtuse at tips; hypanthium tube conspicuous, 0.3–0.5 mm long. Male and female plants quite similar. Male plant: branches robust and sparingly arranged along the stem length, internode 8–12.5 mm long; leaves lax, not imbricate, broadly ovate to triangular, 1–2.5 × 0.5–1 mm; inflorescence lax; hypanthium tube short to non-existent, shorter than perianth lobe tubes, stamen tetramerous, rarely pentamerous; staminal filaments exserted at junction of hypanthium and perianth lobe tubes, about 0.2 mm. Female plants: branches robust, internodes 2–12.9 mm; leaves lax, not imbricate, broadly ovate to triangular, 1–2.2 × 0.5–1 mm; inflorescences spike; hypanthium tubes more conspicuous but shorter than perianth lobe tubes; style stout, 0.3–0.5 mm. Fruit nutlets, truncated to globose, white, attached to the branch by a truncated creamy elaiosome, 2–3.5 × 1.8–2.7 mm, with 5 conspicuous or faint ribs, with or without faint reticulation between the ribs, perianth lobe remnants persistent, green when young but turning yellow to orange with age, equal or shorter than fruit length ( Fig. 8 ).

5.2.2.1.1. Diagnostic characters. Thesium fragile is similar to T. microcarpum and T. quartzicolum but is best compared with the latter in its virgate growth form, brittleness, with male and female plants diffi-cult to differentiate due to similarities, sparse branching, branchlets jointed at node, leaves almost absent and reduced to scales, and inflorescences lax in both male and female plants and distributed along the branch lengths. It differs from T. quartzicolum in its perennial suffrutex growth habit, up to 40 cm tall, (versus herbaceous annual, up to ca 15 cm), robust rootstock, (versus slender rootstock), stem transverse section sulcate (versus terete), fruits truncated to globose, attached to the stem by a white elaiosome, capped with green or yellow to orange (depending on age) persistent perianth segments (fruits ovoid to subglobose, elaiosome absent, green to golden green, capped with green persistent perianth segments,), usually found on coastal well drained sandy soil or sand dunes (versus confined to quartz-silcrete outcrops).

5.2.2.1.2. Distribution and habitat. Thesium fragile occurs mostly along the coastal belts of the GCFR and is endemic to the region. It is restricted to sand dunes and well-drained beach sand from sea level to about 500 m a.s.l. in lowland fynbos vegetation. It has been collected along the coastal hill slopes, beach sand flats and sand dune belts of the GCFR ( Fig. 7A ).

5.2.2.1.3. Conservation status. Von Staden (2015) assessed T. fragile as a data deficient taxon and considered it as taxonomically problematic, probably as the species was poorly known and can easily be confused with T. confusum ( Forest and Manning, 2013) or T. microcarpum . In our assessment, T. fragile is locally abundant in its major habitats and is found in most of the protected coastal reserves with no potential threat so far. Although it is narrowly endemic to the coastal belts of the GCFR, we assess it as least concern (LC) under the IUCN Standards and Petitions Subcommittee (2017) guidelines.

5.2.2.1.4. Additional specimens examined. South Africa. EASTERN CAPE: 3424 ( Humansdorp ): without precise locality (- AA), 29 Mar 1918, ♀ plant, Pillans 3938 ( BOL) ; Palmietvlei (- BB), 09 Aug 1941, ♀ plant, Parker 3577 ( BOL) ; Coastal slopes, Witte Els Bosch (- BD), 01 Dec 1925, ♀ plant, Fourcade 3168 ( BOL) ; Uyshoek (- AB), 15 Mar 1977, ♂ & ♀ plants, Thompson 3420 ( PRE) ; Wilderness dunes (- BB), 03 Dec 1951, Compton 23071 ( BOL, NBG) ; Seal Point Nature Reserve , Cape St. Francis (- BB), 03 Nov 2004, ♂ & ♀ plants, Forest, Trinder-Smith & Cowling 736 ( NBG) .

WESTERN CAPE. 3318 (Cape Town): Oosterval, Langebaan (-AA), 24 Jul 1971, Axelson 459 ( NBG). 3322 (Oudtshoorn): Kleinplaat, George District (-DB), Feb 1879, ♀ plants, Bolus 4759 ( PRE); Homtini Pass, George (-DD), Aug 1926, ♀ plants, Muir 4466 ( BOL). 3323 (Willowmore): De Hoop, Buffelsfontein (-AC), 09 Aug 1984, ♂ & ♀ plants, van Wyk 1790 ( STE). 3418 (Simonstown): near mouth of Palmiet River, Kogelberg Nature Reserve , Kleinmond (-AC), 24 Mar 2008, ♂ plant, Verboom 1305 ( BOL); Harold Porter Botanical Reserve , Betty's Bay (-BD), 24 Sep 1963, ♂ & ♀ plants, Jopper 160 ( NBG); Pringle Bay (-BD), 11 Sep 1969, ♂ & ♀ plants, Boucher 616 ( STE, NBG); Swartklip (-BA), 24 Feb 1972, ♂ & ♀ plants, Taylor 8076 ( NBG, STE); Walker's Bay , littoral dune (− AD), 21 Mar 1973, ♀ plants, Taylor 8365 ( NBG, STE); Hangklip, Rooi-Els (-BD), 11 Mar 1981, ♀ plants, Parsons 54 ( NBG, STE); Gansbaai, Uilkraals river mouth (-CB), 12 Mar 1981, ♀ plants, Parsons 125 ( NBG, STE); Dunes opposite Malkopsvlei, Betty's Bay (-BD), 17 Mar 1983, ♀ plants, van Wyk 1197 ( NBG, STE). 3419 (Caledon): Pearly Beach, (-BC), 10 Jun 1950, Maguire 3 ( NBG); West of Franskraal (-CB), 09 Apr 1979, ♀ plants, Hugo 1703 ( NBG, STE); De Kelders, Gansbaai (-CB), 10 Oct 1981, ♂ & ♀ plants, Mauve & Hugo 132 ( NBG, STE); De Kelders, Gansbaai, near Klipgat pump station, next to disused road to the sea (- AC), 24 Nov 1990, ♂ & ♀ plants, Fellingham 1515 ( STE, NBG); Roadside on the northern outskirts of Gansbaai (-CB), 19 Jun 1995, ♂ & ♀ plants, Paterson-Jones 393 ( NBG); Coastal slopes, Wille Els Bosch, (-CA), 01 Oct 1936, ♂ & ♀ plants, Fourcade 5347 ( STE); De Kelders, Northwest of Klipgat Pump Station (-CB), 14 Apr 1990, ♂ plants, Fellingham 1453 ( NBG, STE). 3420 (Bredasdorp): Papkuilsfontein, Bredasdorp, (-CA), 11 Jan 1956, ♂ plants, Rycroft 1834 ( NBG); Pearly Beach , 10 Jun 1950, ♀ plants, Maguire 30 ( NBG); De Hoop Nature Reserve , Windhoek (-CB), 26 Dec 1946, ♀ plants, Compton 18, 994 ( STE); 3 miles from Arniston to Bredasdorp (-CA), 27 Jul 1970, ♂ & ♀ plants, Merwe 104 ( NBG, STE); Witsand river mouth (-BC), 06 Nov 1979, ♀ plants, Hugo 1909 ( NBG, STE); Agulhas, westward from the light house (-CC), 25 Mar 1982, ♂ & ♀ plants, Fellingham 383 ( NBG, STE); De Hoop Buffelsfontein (-CB), 09 Aug 1984, ♂ & ♀ plants, van Wyk 1784 ( NBG, STE); De Hoop Buffelsfontein (-CB), 29 Apr 1985, ♂ & ♀ plants, Fellingham 1017 ( NBG, STE); Marloth Nature Reserve (-AD), 25 May, 1903, ♀ plants, Pearson 14 ( BOL, NBG); De Hoop Nature Reserve , Whale trail, near Koppie Alleen (-BC), 17 Oct 2004, ♂ plants, Forest & Lucas 715 ( NBG, STE). 3421 (Riversdale): Still Bay , sand dune below rubbish dump, southerly aspect, steep slope, (-CC), 28 Dec 1978, ♂ & ♀ plants, Bohnen 4903 ( STE, NGB); ca 3 km on road from Vermaaklikheid to Puntjie (-BD), 29 May 1984, ♂ & ♀ plants, Callaghan, Fellingham & van Wyk 424 ( NBG, STE); Still Bay , near estuary, (-AD), 11 Jan 19, ♀ plant, Bohnen 4961 ( PRE); Still Bay , Botterkloof, at the road to Riversdale (- AD), 04 May 2006, Mucina 040506/29 ( NBG); Rubbish dumps, Still Bay (-AD), 10 Mar 1980, ♂ plants, Bohnen 7433 ( NBG, STE); road above Panorama circle (-AD), 18 Jul 1980, ♀ plant, Bohnen 7585 ( NBG, STE). 3422 (Mossel Bay): Buffalo Bay , near Walker pond (-AA), 02 Feb 1936, ♀ plants, Guthrie 5347 ( BOL); Groot Brak river mouth (-AA), 13 Nov 1981, ♂ & ♀ plants, Parsons 372 ( NBG, STE). 3423 (Knysna): Forest near Portland , Knysna (-AA), 01 Feb 1929, ♀ plants, Duthie 1103 ( STE); Buffalo Bay , near Knysna (-AA), 29 Apr 1969, ♂ & ♀ plants, Barker 10, 608 ( NBG); Robberg Nature Reserve (-AB), 29 May 1970, ♂ plants, Taylor 7700a ( NBG, STE); Goukamma Nature Reserve (-AA), Feb 1970, ♀ plants, Merwe 1736 ( NBG, STE) .

Figures

Fig. 8. Thesium fragile: (A) growth habit and coastal sand substrate of the plant, (B) closer view of the fruiting female plants, (C) indeterminate flowering shoot with scale-like leaves subtending branchlets, bracts and bracteoles, (D) flowering shoot showing tetramerous flower and stamens in male plant, (E) female shoot borne with truncate whitish fruit capped with yellowish long persistent perianth remnants.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 ▲.