Salacia arenicola Gosline, 2014

Gosline, G. & Cheek, M., 2014, Two new African species of Salacia Salacioideae, Celastraceae, Blumea 59 (1), pp. 26-32 : 26-29

Salacia arenicola Gosline , sp. nov. — Fig. 1 , 2a–c ; Map 1

Diagnosis: Similar to Salacia stuhlmanniana Loes. but differing in several aspects including: having reddish branchlets rather than grey; flowers drying yellow rather than brown-black; stamens twice length of pistil rather than the same length; fruits with a thin (c. 1 mm) leathery vs a thick (3–4 mm) woody exocarp. — Type: Mpandzou , A. L. 1262 (holo IEC; iso K, P, WAG), Republic of Congo, Kouilo Department, Pointe Noire [S4°41'58.9" E11°48'22.6"], 10 July 2011 .

Etymology. The species epithet (‘sand dwelling’) refers to its white sand habitat.

Scandent shrub or liana to 5 m tall, glabrous with copious resin. Shoots terete, lenticellate, twigs dark red. Leaves opposite to subopposite, elliptic to lanceolate, 4 –10 by 1–5 cm, apex rounded to shortly acuminate (acumen to 4 by 3 mm), base attenuate, lamina coriaceous, margin entire or with minute teeth sometimes present towards apex, leaf margin revolute when dried, concolorous, drying light green, upper surface smooth, midrib prominent above and below, 6–8 pairs of secondary veins barely visible above, more prominent below, bending sharply upwards c. 5 mm from the margin, tertiary venation reticulate apparent below, fainter above. Petiole 8–20 mm long, 20– 25 % of the length of the lamina, drying darker than lamina, canaliculate, margins straight, showing a clear dehiscence ring at junction with shoot. Inflorescence an axillary fascicle or glomerule holding 4 –14 flowers on a peduncle 0 –1 mm long, bracts fimbriate less than 0.1 mm long. Flowers yellow 5–7 mm diam, very fragrant smelling of hyacinth at 2 PM (pers. obs. Gosline 10 July 2011); pedicels thin 8–10 mm long; sepals 5, subequal, ovate, 1 mm long, fimbrillate; petals 5, ovate-oblong, 3 by 2 mm, membranaceous, disk green cylindrical (Hallés tronconique (1987: 33)) 0.1 mm tall by 0.3 mm diam with an abrupt upper edge and no impressions above; stamens 3, filaments 3 mm long, not apiculate, thecae 0.1 mm long, confluent at an angle of 90°; style 1 mm long, tapering to a single point; locules 3 each with 2 superposed ovules. Fruits glossy orange spherical 2–3.5 cm diam, fruiting pedicel 0.2–0.6 cm long by 0.4 cm diam; pericarp smooth less than 1 mm thick, flesh sweet, edible; seeds 1(3), spherical 1.2 cm diam when solitary, flattened when multiple.

Distribution & Ecology — Known only from a restricted white sand thicket habitat along the coast of the Republic of Congo, possibly extending into neighbouring Gabon and to be searched for on the coasts of Cabinda, DRC, and Angola.

Representative specimens. GABON, Ogooué-Maritime Province, near beach south of Gamba, Breteler 14951 ( WAG,photo only seen), 6 Nov.1998 ; Gamba, shore of Vevy-lagoon, Wieringa 1169 ( WAG, photo only seen), 15 June 1992 . – REPUBLIC OF CONGO, Kouilo Department, Conkouati, Mpandzou 1862 ( IEC, K), 11 Dec. 2012 ; Djeno, Mpandzou 1784 ( IEC, K), 7 Dec. 2012 ; Fouta , Kami T 1295 , 29 Nov. 2011 ( IEC, K, MO, P, WAG) ; Bas-Kouilou near Madingo-Kayes , Kami T 1342 ( BR, G, IEC, K, MO, P, WAG), 3 Dec. 2011 ; Mvandji, Nkondi 506 ( IEC, K), 13 Apr. 2013 ; Plage Longo-Boudji, Mpandzou 1888 ( IEC, K), 12 Dec. 2012 ; Pointe Noire , Kami T 1270 ( BR, G, IEC, K, MO, P, PRE, US, WAG) , 26 Nov.2011; Tchiele, Nkondi 768 ( IEC, K), 17 Apr. 2013 ; Tchimpounga, Mpandzou 1647 ( IEC), 5 Nov. 2012 .

Conservation assessment — An assessment of Vulnerable (VU B2ab(iii)) is given here using the categories of IUCN (2012). This is on the basis of restricted range (the ten locations listed above, Extent of Occurrence (EOO) 3 400 km 2, Area of Occupancy (AOO) 76 km 2) and continuing development pressure on the habitat at most of the ten locations. The habitat is essentially a narrow linear corridor just inland of the shore. Thanks to the support of the Zanaga project the habitat of S. arenicola in Republic of Congo has been well surveyed; the species has been targeted in five surveys along the entire coast of the Republic of Congo between 2010 and 2013. During this period building of houses north of Pointe Noire destroyed some of the habitat (Van der Burgt pers. comm.). A new port is proposed for the Pointe Indienne area to the north of Pointe Noire and a large oil refinery occupies the southern end of the species range at Djeno. Eight km of this habitat close to the coast is protected by the Tchimpounga Nature Reserve and a small patch has been found in the Conkouati Reserve. The largest known population of the species occurs at Bas-Kouilo where about 50 plants were seen in 2013 (Cheek pers. obs.). The remainder of the range is subject to active exploitation and development especially in the Djeno area where the habitat is being rapidly cleared and may soon be eradicated due to urbanization and activities apparently linked to the Total oil refinery. At Plage Longo-Boudji, Mvandji and Tchiele tourism has resulted in clearance of part of the habitat. However, at Mvandji, Fouta (Van der Burgt pers. comm.) and near Madingo-Kayes (Bas-Kouilo) threats remain low.

The Gamba region in Gabon is an area of large scale oil pro- jects including refineries. The WWF has a project in the area in conjunction with Shell oil which is focussed on control of bush meat trade. The full extent of the white sand habitat and threats in Gabon are unknown.

If present trends continue the species could soon be reassessed as Endangered. Both EOO and AOO are within the range for the IUCN (2012) EN rating which will apply if the number of locations drops to five.

Notes — In the Flore du Gabon S. arenicola specimens key to S. stuhlmanniana , but with clear differences in flowers, fruits and vegetative characters noted in the diagnosis above. Salacia stuhlmanniana has an Eastern African distribution. Hallé (1987) synonymizes S. lomensis Loes. from West Africa, but the latter has smaller leaves and Robson (1966) questions the inclusion. The two populations have identical flowers and fruits and differ only in leaf size and twig surface and we agree with Hallé that they should be considered subspecies.

Also growing in these coastal thickets is S. cornifolia Hook. f. which is found from Liberia to the Congo Republic, primarily in coastal sandy soils. Salacia arenicola is easily distinguished from S. cornifolia by the presence of resinous threads in the leaves, more distinct venation and smooth rounded rather than irregularly shaped fruits.

Other related species found in coastal and subcoastal habitats around Africa (but not sympatric with S. aremicola ) are S. madagascariensis (Lam.) DC. , S. senegalensis (Lam.) DC. and S. kraussii Harv. , all containing resin.

Few Salacias are recorded as scented; this species was discovered because of its strong odour of hyacinth (Hyacinthus). The large glossy bright orange fruits of S. arenicola are edible and probably dispersed by chimpanzees which still occur in its white sand habitat in the Tchimpounga Reserve (Cheek pers. obs. 2012). The leathery pericarp must be pierced to access the refreshing, slightly sweet orange pulp that surrounds and is strongly attached to the usually single seed (Cheek pers. obs. 2012).

Figures

Map 1 Distribution of Salacia arenicola Gosline (▲), S. nigra Cheek (■) and S. mayumbensis Exell & Mendonça (●).

Fig. 1 Salacia arenicola Gosline. a. Habit; b. examples of leaf shape (mature mid-shoot leaves); c. bark from main stem of a; d. inflorescence (from photo- graph); e. inflorescence base showing one flower in situ as seen from above the inflorescence; f. flower, lateral view; g. flower underside showing asymmetric calyx lobes; h. vertical section of newly opened flower; i. stamen, outer face; j. stamen, inner face; k. style, ovary and disk; l. transverse section of ovary; m. transverse section of style; n. infructescence (from photograph); o. transverse section of 2-seeded dried fruit (a–d, f–m: Mpandzou 1262; O Kami T 1270). — Scale bars: a, b, d, l, n, o = 1 cm; c, e–g, i–l = 1 mm; m = 500 µm. — Drawn by Andrew Brown.

Fig. 2 a–c: Salacia arenicola Gosline. a. Habit; b. fruits; c. flowers and stem showing lenticels. — d: Salacia nigra Cheek. Fruiting specimen. — Photos by: a, c: G. Gosline; b: M. Cheek.