Sericanthe chimanimaniensis Wursten & De Block, 2020

Wursten, Bart, Bridson, Diane, Janssens, Steven B. & Block, Petra De, 2020, A new species of Sericanthe (Coffeeae, Rubiaceae) from Chimanimani Mountains, Mozambique-Zimbabwe border, Phytotaxa 430 (2), pp. 109-118 : 110-114

Sericanthe chimanimaniensis Wursten & De Block , sp. nov. ( Figs. 1 , 3 ).

Type:— MOZAMBIQUE. Manica Province: along path to Mt. Peza, slopes below Mt. Dombe , Chimanimani Mts. , 14 May 2011 (fl, fr), B. Wursten & S. Dondeyne BW 241 [holotype BR ( BR5020184241490 ); isotypes BR ( BR5020184242527 ), K, SRGH] .

Diagnosis:—Differing from Sericanthe andongensis by the smaller habit (1–3 m vs. 1–7 m tall in S. andongensis ), the somewhat smaller leaves (2–7 × 1–3.2 cm vs. (3–)5–11.5 × (1.5–) 2.5–6.4 cm), the lower flower merosity (6–8-merous vs. 8(–9)-merous), the shorter calyx (5.5–7 mm long vs. 7–12 mm long), the shorter calyx apiculum (0.5–1 mm long vs. 1–2 mm long), the shorter corolla tube [5.5–9 mm vs. 8–14(–16) mm long] and lobes [7–9.5 mm vs. (7–) 8–12 mm long], the shorter anthers (3.5–4.5 vs. 4.5–6 mm long) and the shorter style [7–12 vs. 13–20(–24) mm long].

Shrub or small tree up to 3 m tall; deciduous, sometimes leafless or leaves immature at time of flowering, leaves clustered at the end of lateral branches or short-shoots, the stems below rugged with many stipular remnants, internodes often short; young stems drying reddish brown, densely covered with short spreading, appressed or rarely erect hairs; older stems with grey-brown bark. Leaves petiolate; petioles 2–7 mm long, moderately to densely covered with appressed hairs; blades elliptic to obovate, narrowly elliptic or narrowly obovate, rarely broadly elliptic, 2–7 × 1–3.2 cm, chartaceous to subcoriaceous, drying brown or green, usually discolorous and somewhat paler below, slightly glossy above; base cuneate, acute or obtuse; apex subacuminate to acuminate with tip 0.2–1 cm long or rarely acute to rounded; blade glabrous, midrib and secondary veins sparsely to moderately pubescent on both sides, or upper side of lamina sparsely appressed pubescent, and lower side sparsely to densely soft pubescent with erect hairs (more appressed on midrib and secondary veins); margin sparsely ciliate; midrib very prominent below; with 3–5(–6) secondary veins on each side of midrib, prominent below; hairy tuft domatia often present; bacterial nodules often visible as short black lines along the midrib near the leaf base. Stipular sheath 1.75–3.5 mm long, the base densely and the upper half moderately covered with appressed hairs or glabrescent outside, with a dense row of colleters interspaced with a few hairs but otherwise glabrous inside, upper half membranaceous, truncate to broadly triangular at tip, keeled; awn needle-like, 0.5–2.5 mm long, rarely with a few appressed hairs on the base. Flowers axillary, solitary, sessile, sweet-scented, 6–8-merous; bracts and bracteoles cupular, arranged in series of 2–3 calyculi, progressively larger towards the top, each with 2 short and 2 long awns; calyculi 2.5–4.5 mm long with short awns 0.3–1 mm and long awns 1–2 mm long, densely covered with appressed hairs outside, especially in the upper half and on the awns, inside with a basal ring of long appressed hairs, sparsely covered with long appressed hairs interspaced with colleters in the lower half and upper half glabrous. Hypanthium cup-shaped, 1.5 mm in diameter, densely covered with long appressed hairs. Calyx ellipsoid in bud, completely enclosing the young corolla, 5.5–7 × ca. 4 mm including an apiculum 0.5–1 mm long, splitting into 2 lobes when the corolla grows out, papyraceous, densely sericeous outside, pubescent inside (vestiture identical to that of bracts and bracteoles). Corolla tube narrowly obconical, 5.5–9 mm long, ca. 1.5 mm in diameter at the base, ca. 3 mm in diameter at the mouth, sericeous outside, except for the base densely covered with long, spreading, interwoven hairs inside; lobes oblong, 7–9.5 × 3–4 mm, glabrous inside, sericeous outside, margins ciliate, tip blunt and emarginate with central acumen. Ovary bilocular; placentas attached to upper half of septum, with (1–)2 impressed ovules. Filaments 1–2 mm long, glabrous; anthers linear, 3.5–4.5 mm long. Style 7–12 mm long, glabrous or with a few long hairs; stigmas linear, 1–1.5 mm long, spreading at anthesis. Fruit sessile, globose, 9–10 mm in diameter, with remnants of persistent calyx, sparsely covered with appressed hairs, red at maturity. Seeds 1–2 per fruit, subglobose or hemiglobose, 5–7 mm in diameter, orange-brown; hilum subcircular.

Habitat:—Growing among quartzitic boulders or on quartzitic sandy soils, at elevations <500 m in Brachystegia woodland, or at (250–) 950–2150 m elevation, in fairly exposed conditions.

Distribution:—Restricted to the quartzitic sandstone areas of the Chimanimani Mts. along the border of Mozambique and Zimbabwe ( Fig. 2 ).

Phenology:—Flowering specimens were collected in May, August–October; and fruiting specimens in April– December (probably throughout the year). Fruiting specimens usually bear young flower buds.

Preliminary IUCN assessment:—Endangered: EN B1b(iii) + 2b(iii). Using a cell width of 2 km, the extent of occurrence (EOO) of Sericanthe chimanimaniensis is estimated to be 462 km 2 and its area of occupancy (AOO) 68 km 2, which both comply with the criteria for the Endangered category under sub-criteria B1 and B2. The species occurs in four locations, two of which are located within the protected Chimanimani Mountains National Park. The main threats to the environment in the Chimanimani Mts. are caused by temporary and long-term settlement of people involved with alluvial goldmining. This leads to soil disturbance and erosion, particularly along river banks, increased wildfires, hunting and trapping of animals as well as wood collection for building and firewood. The specific habitat of Sericanthe chimanimaniensis among quartzitic sandstone rocks is not much affected by either mining activities or fires, and the trees are generally too small to yield adequate firewood or building material. However, over time the presence of larger numbers of people working and living in the area will likely have a negative impact.

Specimens studied:— MOZAMBIQUE. Manica Province: Chimanimani Mts., 1693 m, - 19.775944S, 33.099083E, 29 April 2016 (fr), Banze, Valdemar & Cacilda 402 ( K, LMA n.v.) ; Chimanimani Mts., 1895 m, - 19.736000S, 33.098722E, 3 May 2016 (fr), Banze, Valdemar, Cacilda 436 ( K, LMA n.v.) ; track from Nhabawa Village to Chikukwa, Chimanimani foothills, Sussendenga District , 935 m, - 19.712222S, 32.999444E, 9 April 2010 (fr), J. Burrows & S. Burrows 11696 ( BNRH scan, LMA n.v., PRE n.v.) ; highest point of the track from Nhabawa Village to Chikukwa, Musapa Gap , Chimanimani Mts. , 990 m, - 19.715278S, 32.981389E, 9 April 2010 (fr), J. Burrows & S. Burrows 11712 ( BNRH scan, LMA n.v., PRE n.v.) ; Musapa gap, Chimanimani Mts. , 975 m, - 19.714900S, 32.980100E, 6 October 1950 (fl), Chase 2961 ( SRGH) ; slopes of Mt. Binga , Chimanimani Mts., 1600 m, 3 July 2009 (fl), Dondeyne s.n. (site observation only, photographs available at: https://www.mozambiqueflora.com/speciesdata/ species.php?species_id=155620) ; floresta Thekeza a 200 m do acampamento seguindo o caminho local na escalagem da montanha rodeado de pedras, Chimanimani Mts. , 468 m, - 19.909194S, 33.189472E, 24 June 2015 (fr), Massunde, Banze & Cheek 6 ( K, LMA n.v.) ; northwestern slopes between Mt. Dombe and Mt. Peza , Chimanimani Mts., 1634 m, 19.743056S, 33.013444 E, 17 April 2014 (fr), Matimele, Wursten, Mapaura, Ballings, Timberlake & Hadj-Hammou 2059 ( BR, K, LMA n.v., SRGH) ; small pass on ridge N of Mt. Peza , Chimanimani Mts., 1889 m, - 19.742750S, 32.999861E, 18 April 2014 (fr), Matimele, Wursten, Mapaura, Ballings, Timberlake & Hadj-Hammou 2074 ( BR, K, LMA n.v., SRGH) ; Sussundenga district , E of Makurupini river, Chimanimani Mts. , 270 m, - 20.006920S, 33.048530E, 11 June 1971 (fr), Müller & Gordon 1849 ( LISC, SRGH) ; Chimanimani Mts., 1694 m - 19.756390S, 33.094200E, 2 May 2016 (fr), Osborne, Brummitt, Massunde, Nhahedzi & Shah 1165 ( K, LMA n.v.) ; Chimanimani Mts., 1710 m, - 19.752550S, 33.089090E, 6 May 2016 (fl), Osborne, Massunde, Muassinar, Nhahedzi & Shah 1214 ( K, LMA n.v.) ; path to Mt. Peza , Chimanimani Mts., 1560 m, - 19.744139S, 33.015619E, 14 May 2011 (fl, fr), Wursten & Dondeyne BW 171 ( BR, K, SRGH) ; Mevumodzi valley near Eastern Lakes, Eastern Chimanimani Mts., 1260 m, - 19.789800S, 33.134770E, 28 October 2014 (fl), Wursten, Mapaura, Timberlake & Mutasa BW 1057 ( BR, K, LMA n.v., SRGH) ; hillside above small valley NE of Mt. Binga , Chimanimani Mts., 1747 m, - 19.753190S, 33.094360E, 22 April 2014 (fr), Wursten, Ballings, Mapaura, Timberlake, Hadj-Hammou & Matimele PB 2303 ( BR, K, LMA n.v., SRGH) . ZIMBABWE. Manicaland Province: The Corner , Chimanimani Mts., 1250 m, - 19.674950S, 32.968150E, 13 October 1950 (fl), Bennett s.n. ( K n.v., SRGH) ; ca. 1 mile NE of mountain hut on slopes below Turret Towers , Chimanimani Mts., 1676 m, - 19.799700S, 33.038260E, 5 April 1969 (fr), Kelly 72 ( K, SRGH) ; Chimanimani Mts. , 915 m, 15 August 1948 (fl), McGregor 57/48 ( FHO scan) ; Mussapa Gap, The Corner, Chimanimani Mts. National Park ca. 17 miles NNE of Melsetter, 1067 m, - 19.704100S, 32.956700E, 31 August 1961 (fl), Methuen 171 ( K) ; ascent to Chimanimani Mts., 1380 m, - 19.789010S, 32.995870E, 28 November 1983 (fr), Müller & Best 3767 ( SRGH) ; mountain hut, Chimanimani Mts., 1645 m, - 19.784200S, 33.018700E, 27 May 1959 (fl, fr), Noel 2136 ( SRGH) ; Chimanimani Mts. , 1 October 1970 (fr), Plowes 3440 ( SRGH) ; Chimanimani Mts. , above Musappa Gap , 1300 m, - 19.707200S, 32.962600E, December 1955 (fr), Stables 9/55 ( COI scan, K scan, SRGH) ; Chimanimani Mts., 2133 m, 25 September 1906 (fl), Swynnerton 641 ( BM scan, K n.v., SRGH) ; Mount Pene or Singweke (see critical note 2), 7000 ft, 13–15 October 1908 (st), Swynnerton 6068 ( BM scan) ; lower northern slope “ Uncontoured Peak ”, Chimanimani Mts., 1828 m, - 19.772100S, 32.034800E, 16 September 1956 (fl, fr), Taylor 1761 ( SRGH) ; Chimanimani Mts., 1825 m, - 19.772100S, 33.034800E, 8 June 1949 (fl, fr), Wild 2945 ( BR, K, SRGH) ; The Corner , Chimanimani Mts., 1250 m, - 19.674950S, 32.968150E, 13 October 1950 (fl), Sturgeon 30662 [ BR (as Sturgeon s.n.), K, MO n.v., SRGH] ; Chimanimani Mts. National Park , 1600 m, 21 September 2011 (fl), Lagarde s.n. (site observation only, photographs at: https://www.zimbabweflora.co.zw/ speciesdata/species.php?species_id=155620) ; Chimanimani Mts. National Park , 1480 m, - 19.740217S, 32.976407E, 16 May 2011 (st), Wursten & Dondeyne s.n. (site observation only) .

Critical notes:—1. Most specimens of S. chimanimaniensis occur at elevations between 1000 and 1900 m. However, Matimele et al. 2074 and Banze et al. 436 from Mozambique occur at at 270 m and 468 m respectively, in Brachystegia tamarindoides Bentham (1866: 312) woodland amongst quarzitic boulders. On the Mozambique side the quartzitic geology and its affinities reach much lower elevations than on the Zimbabwe side of the Chimanimani Mts. , hence the lower occurrence of S. chimanimaniensis there. ─ 2. The specimen label of Swynnerton 6068 gives the location ‘Mount Pene or Singwekwe’. According to Swynnerton’s notes, Pene Mountain “is separated from the Chimanimani by the gorge of the Haroni” and has a “single grassy peak, 7000 ft above sea-level” ( Rendle et al. 1911: 3). Swynnerton’s location clearly differs from what is now known in Zimbabwe as Peni or Pene Mountain, located southwest of the Chimanimani Mts. and only reaching an elevation of ca. 1500 m (vs. 2134 m). Swynnerton’s location is not included in the distribution map since it could not be pinpointed exactly. ─ 3. Burrows et al. (2018: 1033) were aware of our plans to formally describe S. chimanimaniensis and added the species in an addendum to Trees and Shrubs Mozambique. They referred the name to “Wursten & De Block, in press (2017)”. Although Burrows et al. (2018) gave a relatively detailed description of the species, they did not indicate a type; therefore, the name S. chimanimaniensis was not validly published by them.

Figures

FIGURE 1. Sericanthe chimanimaniensis Wursten & De Block. A, flowering branch; B, stipule; C, flower; D, detail of cupular bracteoles and longitudinally split calyx; E, ovary and longitudinally split calyx; F, placenta with two ovules, abaxial view; G, placenta with two ovules, adaxial view; H, fruit; I, seed, adaxial view; J, seed, abaxial view. Drawing by Antonio Fernandez. A–I, Wursten & Dondeyne BW241 (BR).

FIGURE 2. Distribution map of Sericanthe chimanimaniensis Wursten & De Block.

FIGURE 3. Sericanthe chimanimaniensis Wursten & De Block. A, habitat; B, habit; note the absence of new leaves at the time of flowering; C, flowers. Photographs: A, S. Dondeyne; B, C, B. Wursten.