Paracephaelis trichantha (Baker) De Block

Block, Petra De, 2022, Monograph of the western Indian Ocean genus Paracephaelis (Rubiaceae - Pavetteae), with description of thirteen new species, European Journal of Taxonomy 801, pp. 1-99 : 83-88

Paracephaelis trichantha (Baker) De Block

Fig. 22

Systematics and Geography of Plant s 73: 100 ( De Block 2003); Flora Zambesiaca, Rubiaceae, Part 3: 619, tab. 122 ( Bridson 2003); Trees & Shrubs Mozambique: 1015 ( Burrows et al. 2018).

Basionym

Pavetta trichantha Baker , Bulletin of Miscellaneous Information, Kew 1894 (89): 148 ( Baker 1894); Abhandlungen der Senckenbergischen Naturforschenden Gesellschaft 21: 91 ( Schinz 1897); Abhandlungen der Senckenbergischen Naturforschenden Gesellschaft 26: 552 ( Voeltzkow 1902); Bulletin of Miscellaneous Information, Kew 1919 (3): 123 ( Hemsley 1919). Type: SEYCHELLES – Aldabra islands • s.loc.; Oct.–Dec. 1892; fl, fr; Abbott s.n.; lectotype: K, here designated; isolectotypes: P[P00885879], US[US00138555].

Homotypic synonym

Tarenna trichantha (Baker) Bremek., Repertorium Novarum Specierum Regni Vegetabilis 37: 207 ( Bremekamp 1934); Philosophical Transactions of the Royal Society, Biological Sciences 260: 218, 225 ( Fosberg 1971); Philosophical Transactions of the Royal Society, Biological Sciences 260: 231 ( Renvoize 1971); Phytologia 41: 355 ( Fosberg 1979); Kew Bulletin 34: 401, figs. 2F, 3V–W ( Bridson 1979); The Flora of Aldabra and Neighbouring Islands: 161 ( Fosberg & Renvoize 1980); Bulletin du Jardin botanique national de Belgique 55: 102, figs 7–9 ( Bridson & Robbrecht 1985); Flora of Tropical East Africa, Rubiaceae, Part 2: 602 ( Bridson 1988); Kenya Trees, Shrubs and Lianas: 547 ( Beentje 1994); Flora des Seychelles: Dicotyledones: 604, pl. 194 ( Friedmann 1994).

Other material studied

SEYCHELLES – Aldabra Atoll • s.loc.; pubescent form; 1892; fl, fr; Abbott s.n.; K, P • s.loc.; pubescent form; 28 Dec. 1906; fl; Dupont 87; K • s.loc. (from living material at Conservatoire et Jardins botaniques de Nancy); 23 Oct. 1996; st; Friedmann 833385; UPS • s.loc.; pubescent form; 1909; fl; Fryer 86; K • s.loc.; glabrous form; 1973; fl; Hnatiuk 732022; US online • Anse Grande ; pubescent form; 2 Mar. 1973; fr; Hnatiuk 732026; US online. – Grande Terre (South Island) • Cinq Cases ; glabrous form; 18 Jan. 1968; fl; Fosberg & Grubb 48885; US online • SE of Cinq Cages camp, 300–500 m from coast; glabrous form; 18 Jan. 1968; fl; Fosberg 48911; MO, US online • just SE of Cinq Cases camp, 200–500 m back of coast; glabrous form; 19 Jan. 1968; fl; Fosberg 48921; MO, US online • ibid.; glabrous form; 19 Jan. 1968; fl; Fosberg 48924; MO, US online • just ENE of Cinq Cases camp; glabrous form; 23 Jan. 1968; fl; Fosberg 49023; US online • point Hodoul ; glabrous form; 25 Jan. 1968; st; Fosberg 49048; US online • 5 km W of point Hodoul; glabrous form; 4 Feb. 1968; fl; Fosberg 49209; MO, US online • 3.5 km W of point Hodoul; glabrous form; 4 Feb. 1968; st; Fosberg 49210; US online • SE coast, 0.6 km E du bord de la mer Takamaka; glabrous form; 7 Feb. 1968; fl; Fosberg 49246; MO, US online • Takamaka area ; glabrous form; 7 Feb. 1968; fl, fr; Fosberg 49249; US online • Takamaka well ; glabrous form; 8 Feb. 1968; fr; Fosberg 49259; MO, US online • Takamaka well ; glabrous form; 12 Feb. 1968; fl; Fosberg 49346; MO, US online • S of Takamaka grove; glabrous form; 16 Feb. 1968; fl; Fosberg 49383; MO, US online • dune Jean-Louis , landwards of dunes ; glabrous form; 18 Feb. 1968; fl, fr; Fosberg 49387; MO, US online • ibid.; glabrous form; 18 Feb. 1968; fl; Fosberg 49388; MO, US online • N de Anse Mais; glabrous form; May 1983; fl; Friedmann 4550; P • environs de la dune Jean-Louis ; glabrous form; May 1983; fl; Friedmann 4733; P • vicinity of dune Jean-Louis ; glabrous form; 3 Mar. 1974; fl; Hnatiuk 731506; US online • Takamaka grove; glabrous form; 8 Aug. 1974; fr; Hnatiuk 731706; US online • near Willson’s well; glabrous form; 19 Sep. 1974; fr; Hnatiuk 731899; US online • near Takamaka grove; glabrous form; 25 Mar. 1974; fl; Hnatiuk 732054; US online • Takamaka grove ; glabrous form; 20 Aug. 1973; fr; Merton 7047; K • along trail from hut at dune de Messe to lagoon; glabrous form; 12 Aug. 1992; fr; Potter & Harrington 920812-08-01; P online • SE coast, 0.6 km E du bord de la mer, Takamaka area ; glabrous form; 30 Jan. 1968; fl; Renvoize 873; K, US online • Cinq Cases dune ; glabrous form; 3 Feb. 1968; fr; Renvoize 914; BR, K, L, LISC, P, US online • Cinq Cases dune , 50 yards NE of dune; glabrous form; 3 Feb. 1968; fl; Renvoize 915; K, P, US online • near coast, 0.4 km N of point Hodoul; glabrous form; 10 Feb. 1968; fl; Renvoize 1006; BR, K, L, LISC, P, US online • S of Takamaka; glabrous form; 24 Feb. 1968; fl; Renvoize 1117; BR, K, L, LISC, P, UPS, WAG • near dune Jean-Louis; glabrous form; 14 Mar. 1968; fr; Renvoize 1308; BR, K, L, LISC, P, US online • dune de Messe ; glabrous form; 22 Mar. 1968; fr; Renvoize 1394; K • Trou Nenez ; glabrous form; 20 Aug. 1967; fr; Stoddart 976; K, P, US online. – Euphrates (Esprit Island) • near W end of island; pubescent form; 13 Jan. 1968; fl; Fosberg 48770; MO, US online • s.loc.; glabrous form; Jun. 1983; fl; Friedmann 4823; P. – Michael (Michel Island ) • s.loc; pubescent form; 15 Feb. 1968; fl; Fosberg 49352; MO, US online • s.loc.; pubescent form; 15 Feb. 1968; fr; Fosberg 49355; MO, US online • around coconut / Casuarina grove ; pubescent form; 15 Feb. 1968; fl; Renvoize 1045; BR, K, L, LISC, P, US online. – Picard (West Island) • près bassin Lubines ; pubescent form; May 1983; fr; Friedmann 4548; P • along back path ; pubescent form; Jan. 1974; fl; Hnatiuk 731508; US online • path to bassin Cabri ; pubescent form; 8 Aug. 1973; fr; Merton 7018; K • along back path ; pubescent form; 11 Feb. 1992; fl; Potter & Harrington 920211-08; P online • behind settlement; pubescent form; 12 Jan. 1968; fl; Renvoize 739; BR, K, L, LISC, P, US online • bassin Cabri ; pubescent form; 15 Mar. 1972; fl; Wood 1664; US online. – Malabar (Middle Island) • E end of island; pubescent form; 27 Jan. 1968; fl; Fosberg 49073; MO, US online • près camp Gionnet ; pubescent form; 1983; st; Friedmann 4705; P • N of dune Blanc; glabrous form; s.dat.; fl; Hnatiuk 731504; US online • s.loc.; glabrous form; 27 Jul. 1973; fl; Hnatiuk 732028; US online • s.loc.; pubescent form; 10 Jun. 1992; fr; Potter & Harrington 920610-01; P online • SW corner, W of passe Houareau, along lagoon trail coccid transect; pubescent form; 13 Sep. 1992; fr; Potter & Harrington 920913-05; P online • 250 m W of middle camp; pubescent form; 19 Jan. 1972; fl; Wood 1636; K, US online. – Polymnie Island • s.loc.; pubescent form; 21 Mar. 1974; fl; Hnatiuk 731314; US online • NW corner of island on ridge ca 200 m E of grande passe and 30 m S from edge of sea cliff along northern edge of island; pubescent form; 7 Jul. 1992; fr; Potter & Harrington 920707-07; P online. – Cosmoledo Atoll • s.loc.; glabrous form; s.dat.; Dupont 279; K. – Astove Island • Grand Anse ; pubescent form; 5 Mar. 1968; fr; Fosberg 49720; MO, US online • behind coconut grove N of settlement; pubescent form; 5 Mar. 1968; fr; Renvoize 1204; BR, K, L, LISC, P, US online • s.loc.; pubescent form; 5 Nov. 1968; fl; Ridgway 92; US online. – Assumption Island • s.loc.; glabrous form; Jul. 1910; fr; Dupont 116; K • centre of W coast, along tractor path; glabrous form; 9 May 1973; fl; Frazier 608; US online • 200 m inland of south settlement; pubescent form; 29 Nov. 1973; fl; Frazier 716; US online • centre of island ; pubescent form; 30 Nov. 1973; fl; Frazier 747; US online .

African mainland

KENYA – K7 • Lamu district, Kitwa Pembe hill ; 0–50 m a.s.l.; glabrous form; 15–16 Jul. 1974; fr; Faden R.B. & A.J. 74/1104; K, WAG • Tana river, Shekiko ; 5 m a.s.l.; pubescent form; 21 Aug. 1988; fr; Luke & Robertson 1376; EA, K • Lamu district, Ras Tenewi ; 20 m a.s.l.; glabrous form; 22 Nov. 1988; fr; Luke & Robertson 1436; EA, K • Lamu district, Kiwayu, KWS/WWF Camp ; 20 m a.s.l.; glabrous form; 18 Nov. 1998; fl; Luke 5483; K • Lamu district, Pate Island ; pubescent form; Jul.–Aug. 1980; fl; Marquis s.n.; K • N coast, Kijini conservancy (02° S, 40° E); glabrous form; 10 Nov. 2006; fr; Dowsett-Lemaire 2034; BR .

MOZAMBIQUE • Tecomaze Island ; glabrous form; 29 Mar. 1961; fl; Gomes e Sousa 4673; COI, K, PRE n.v . • Nampula, Mossuril district, Matibane, entre a floresta de Crucsee (Cruce) e a Praia; pubescent form; 20 Feb. 1984; fl; Groenendijk, De Koning & Dungo 1188; K, MO, WAG .

TANZANIA – T6 • Uzaramo district, Wazo hill , ca 25 km NNW of Dar es Salaam; 75 m a.s.l.; pubescent form; 3 Aug. 1969; fr; Harris & Tadros 3038; BR, K • Pwani, Bagamoyo district, Kiono Forest Reserve ; glabrous form; 25 Aug. 1989; st; Rulangarana, Mbago & Suleiman 267; WAG .

Description

Shrub or small tree, to 4 m tall; pubescence white. Young shoots brown or dark brown, moderately to densely covered with short appressed or spreading hairs or glabrous except in the region of the nodes (there moderately or sparsely covered with short appressed hairs); older branches corky, glabrous, pale brown, greyish brown, brown or fawn, flaking. Petioles 7–22 mm long, moderately to sparsely covered with ± long appressed hairs. Leaf blades obovate, elliptic, somewhat ovate or rarely suborbicular, (2.5–)3.5– 13 × 2.5–8 cm, coriaceous, drying brown and not discolorous, upper surface glossy, moderately to densely covered with short erect hairs (appressed hairs in young leaves), glabrous or with pubescence restricted to midrib, secondary veins and margin, lower surface densely to moderately covered with long erect hairs or glabrous except for midrib and secondary veins; margin sparsely ciliate; base cuneate, obtuse or rarely rounded; tip rounded or obtuse and mucronate, or, retuse; hair tuft or ciliate pit domatia often present; midrib moderately to sparsely covered with long appressed hairs or glabrous above, sparsely to densely covered with long appressed hairs below; 6–10 secondary veins on each side of midrib, usually glabrous but rarely with sparse appressed hairs above, somewhat raised and moderately to sparsely covered with ± long appressed hairs below; in case of glabrous leaves, higher order venation conspicuous below because of paler colour, glabrous above, glabrous or very sparsely covered with ± long appressed hairs below. Stipules triangular with needle-like awn, outer surface moderately to sparsely covered with short appressed hairs, or, more often, pubescence restricted to the base and the region of the midrib, inner surface glabrous with row of colleters interspaced with long hairs at the base; sheath 1.5–3 mm long; awn 0.5–2 mm long. Inflorescences sessile, 1.5–7 × 1.5–11 cm, with numerous flowers; inflorescence parts densely covered with ± long appressed or somewhat spreading hairs; first order axes 0.3–3.5 cm long; higher order bracts with stipular parts absent and foliar parts linear, 0.75–2 mm long (up to 4 mm long in second order bracts); bracteoles on pedicel just below ovary, opposite, stipular parts absent, foliar parts linear, 0.5–0.75 mm long, tips acute. Flowers sessile or shortly pedicellate, pedicels 0–2 mm long. Calyx densely covered with short appressed hairs outside; tube ca 0.2 mm long, inner surface with ring of long appressed hairs; lobes triangular, 0.25–0.5 mm long, inner surface sparsely covered with appressed hairs, tips obtuse. Corolla tube 3.5–5.5(–6) mm long, inner surface moderately covered with long erect hairs in upper half; lobes 1.2–2 mm long. Anthers 1.5–2 mm long, completely exserted from corolla tube at anthesis (spreading on top of corolla lobes); filaments 0.1–0.2 mm long; connective often drying reddish brown. Ovary 0.75–1 mm long, densely covered with short appressed hairs; per locule 1–3 ovules pendulous from small placenta attached to upper half of septum. Style and stigma 6.5–11 mm long, exserted for 3–5 mm; style densely covered with long erect hairs from ca 2 mm above base to ca 2 mm below papillate zone; stigmatic lobes 2.5–3 mm long, upper 1.5–2 mm fusiform; papillate grooves running along fusiform part and further down for ca 1 mm. Fruits 0.3–0.4 × 0.4–0.5 cm, wrinkled when dried, moderately to densely covered with short appressed hairs; fruit wall thin, with sclerified vascular bundles; pyrenes hemispherical, ca 3 mm in diam., parenchymatous adaxially, thinly crustaceous abaxially, with rounded base, truncate tip, and small adaxial opening somewhat above the middle. Seeds (1–)2–4 per fruit, 2–3.5 × 1.5–2.5 mm.

Distribution

Occurring on the African mainland along the coast in Kenya, Tanzania, and Mozambique as well as on the islands of the Aldabra group (Outer Islands of the Seychelles), notably on Assumption Island, Cosmoledo Atoll, Astove Island, and Aldabra Atoll (islands Grande Terre, Malabar, Picard, Euphrates, Michael, Polymnie) ( Fig. 25 ).

Habitat and phenology

Thicket, mixed open and closed scrub; on limestone (outcrops and coral champignons), more rarely on sand; elev. 0– 650 m. Flowers: November–February(–July); Fruits: February–December. Most specimens flower in January and February. Anthetic flowers were also collected in November (4 specs), March (5 specs), May (3 specs); June (1 spec.), and July (2 specs).

Provisional IUCN assessment

Vulnerable: VU B2ab(iii). This assessment is based on 74 collections with detailed locality data, out of 81 collected between 1892 and 2006. The EOO of P. trichantha cannot be estimated using GeoCAT since the species is coastal and most of the EOO calculated automatically is part of the Mozambique Channel. The EOO is estimated to be 3680 km 2 and comprises the combined surface area of the Aldabra Atoll, Assumption Island, Astove Island, and the Lamu Archipelago (ca 180 km 2) as well as a 2 km wide strip along the east coast of Africa from 2° to 15° S (3500 km 2). This EOO complies with the Endangered category under criterion B1. The AOO is 136 km 2, which also complies with the Endangered category under criterion B2. The species occurs in 10 locations (the different islands of the Aldabra and Astove Atolls are counted as single locations), which is the upper limit for the Vulnerable category under subcriterion ‘a’ of criterion B2. Most specimens of P. trichantha are collected from the Aldabra Atoll, a world heritage site, which is well-protected as a result of its remoteness. Invasive alien species, climate change, and oil spills are possible threats to P. trichantha on this atoll ( World Heritage List 2020). The natural vegetation on the Assumption and Astove Islands, which are vulnerable for the same threats, is much less preserved ( Ministry of Environment, Energy and Climate Change 2020) and this is also the case for the locations along the east African coast. Coastal forest in east Africa is under high anthropogenic pressure and the once continuous forest cover has been reduced to small remnant patches ( Burgess et al. 1998; Habel et al. 2017). Forest clearance occurs for subsistence farming, agro-forestry plantations, the development of tourist infrastructure, mining (e.g., Wazo Hill in Tanzania; Richard & Nyundo 2018). Less destructive threats are logging for construction wood, firewood or the production of charcoal, the gathering of edible and medicinal plants, hunting, and the collection of honey ( Burgess et al. 2000; Habel et al. 2017). The main threat to P. trichantha is the destruction of its habitat for subsistence farming and the above-mentioned factors, especially on the east coast of continental Africa. A reduction in the extent and quality of the habitat is therefore inferred. This fact, together with the low AOO and the low number of locations, qualifies this species as Vulnerable.

Notes

1. In Paracephaelis trichantha , a glabrous and a pubescent form occurs . In the Aldabra Atoll, specimens of the glabrous form are restricted to South Island, whereas specimens of the pubescent form occur on all islands of the Aldabra Atoll except for South Island. The two forms mainly differ in the presence or absence of pubescence on the young shoots and on the lower and upper leaf surfaces. Furthermore, specimens of the pubescent form tend to have somewhat smaller leaves, inflorescences, and flowers than those of the glabrous form and their stems are brown, greyish or pale brown vs pale brown to fawnish. Both forms of P. trichantha occur on the African mainland, in Tanzania, Kenya, and Mozambique.

2. Like in Paracephaelis cinerea , the anther connective in P. trichantha often dries reddish brown.

3. As mentioned in Note 5 of Paracephaelis comorensis sp. nov., the author initially considered P. cinerea , P. comorensis sp. nov. and P. trichantha as belonging to the same species. This resulted in the annotation of specimens of P. trichantha as “ Paracephaelis cinerea subsp. trichantha ”, a name which was never published.

Figures

Fig. 22. Paracephaelis trichantha (Baker) De Block. A. Flowering branch. B. Stipule. C. Bract, bracteole, ovary and calyx. D. Corolla, stamens, style and stigma. E. Fruit. Drawn by Mr A. Fernandez. From Fosberg 49387 (A), Fosberg 49259 (B), Renvoize 1006 (C–D) and Renvoize 1308 (E).

Fig. 25. Distribution map of Paracephaelis trichantha (Baker) De Block. A. Overview. B. Detail: islands of the Aldabra group.