Ternstroemia cameroonensis ( Ternstroemiaceae ) , a new medicinally important species of montane tree , nearly extinct in the Highlands of Cameroon

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INTRODUCTION
René Letouzey was the most far-ranging and prolific of all the field botanists of Cameroon.On 29 November 1974 he came across a mysterious tree in flower and fruit in a remnant forest patch in the Cameroon Highlands.He collected specimens near the settlement of Fossimondi, in present-day SW Region of Cameroon, as Letouzey 13380, considering it to be a Flacourtiaceae.
H. Sleumer later identified the specimen (in litt., YA, det. 1975) as Ternstroemia polypetala Melch.(then placed in Theaceae), a species hitherto only known from the area of the Uluguru Mts of the Eastern Arc Highlands of Tanzania (Melchior 1934, Verdcourt 1962, Letouzey 1977).Later it was discovered from adjoining northern Malawi (White et al. 2001).This was another case of a remarkable montane range disjunction, comparable with that of, e.g., Alchemilla fischeri Engl., first discovered on several peaks of Kenya, before being found by Letouzey near the summit of Mt Oku in NW Region of Cameroon, the populations separated from each other by almost the whole width of central Africa (Cheek et al. 2000).
Twenty years later the first author, seeking to identify a strange tree from a fruiting specimen collected near the forests of Ijim by Martin Etuge (Etuge 3557) in 1996 as part of an inventory of species for the intended 'Plants of Mt Oku and the Ijim Ridge' (Cheek et al. 2000), discovered it to be the same taxon as Letouzey's.This prompted a re-assessment of the Cameroonian material: was it really conspecific with that from Tanzania?The conclusion after careful comparison with the Tanzanian material was that there are sufficient morphological differences to justify erection of a new species for the Cameroonian material named below as Ternstroemia cameroonensis Cheek.Many of the characters separating the two species (see Table 1) were first elucidated by Letouzey (1977).Letouzey may have published his specimen as a new species or subspecies had he not been influenced by Sleumer's determination and by the fact that only a single gathering from a single plant was available to him (Letouzey 1977).
Realising that the putative new species was extremely rare and threatened, the first author sought to obtain its protection.Etuge was requested to return in 1999 to the site at Ijim at which he had collected Etuge 3557, so as to refind the tree.This resulted in the discovery that the tree had been cut down, and that the forest patch in which it had grown had been reduced by two thirds.Searches for the Ternstroemia over two days in the Ijim area by a large team of botanists, including Etuge, failed to find another plant of the species (Cheek in Cheek et al. 2000: 74-75).The second author, leading teams conducting a botanical survey of the Lebialem Highlands (Harvey et al. 2010) near to the Letouzey site at Fossimondi, made several attempts between 2002 and 2005 to rediscover Letouzey's forest patch and to refind the Ternstroemia, but failed and concluded that it also had been destroyed (Pearce in Harvey et al. 2010: 43).Intensive botanical surveys in other surviving highland forest areas of the Cameroon Highlands over 1997-2011 also failed to find any sign of Ternstroemia (Cable & Cheek 1998, Cheek et al. 2004, 2010, Harvey et al. 2004, 2010).There was every reason to think that the Ternstroemia was extinct and therefore that there was no urgency to describe it as new.
However, in 2013 the third author, a researcher in traditional medicinal plants, already familiar with the species in the wild since 2002, brought a sample (Tacham s.n.) for botanical identification to the National Herbarium of Cameroon (YA).Here it was identified by the second author as the new Ternstroemia, not, after all, extinct.The second and third authors made a joint visit to the only known surviving population in May 2015.The site seemed to be close to the original Letouzey site but not identical with it, supported by the composition of associated species at the two sites being different.
The genus Ternstroemia is pantropical with c. 100 species.Most of the species occur in tropical and subtropical Americas, with others in S and E Asia (Stevens 2001onwards, Weitzman et al. 2004).Only two species have been recognised from Africa and none from Madagascar (Weitzman et al. 2004).Ternstroe mia Ternstroemia cameroonensis (Ternstroemiaceae), a new medicinally important species of montane tree, nearly extinct in the Highlands of Cameroon africana Melch. is known from the littoral from north of the Congo River to the Niger, and T. polypetala from the Uluguru Mts of Tanzania to northern Malawi (White et al. 2001).The genus was formerly included in Theaceae together with Ficalhoa Hiern (now usually placed in Sladeniaceae), e.g., in Verdcourt (1962).
Ternstroemia is now placed in Ternstroemiaceae (Ericales) together with Balthasaria Verdc.(also Tropical Africa) and in Macaronesia Visnea L.f. (Weitzman et al. 2004).The remaining nine genera of Ternstroemiaceae occur mainly in Tropical Asia, but with two genera restricted to the Neotropics (Weitzman et al. 2004).By some Ternstroemiaceae is merged with Pentaphylacaceae where the latter unfortunately takes preference (nom.cons.)(Stevens 2001onwards, Culham 2007).However, the sister relationship of Ternstroemiaceae and Pentaphylacaceae and hence the possibility to merge them is quite uncertain (Stevens pers. comm.).

MATERIALS & METHODS
All specimens cited have been seen by the authors unless indicated n.v.Herbarium citations follow Index Herbariorum (Thiers et al. continuously updated) and binomial authorities IPNI (continuously updated).The conservation assessment was made using the categories and criteria of IUCN (2012).Herbarium material was examined with a Leica Wild M8 dissecting binocular microscope fitted with an eyepiece graticule measuring in units of 0.025 mm at maximum magnification.The drawing was made with the same equipment using Leica 308700 camera lucida attachment.Ternstroemia polypetala sensu Letouzey (Letouzey (1977) 6; Cheek in Cheek et al. (2000) 165; Cheek (2000a)).Ternstroemia sp.nov.Cheek (Cheek & Onana (2011)  Monoecious tree 10 -15 m tall (Letouzey 13380), glabrous.Crown hemispherical, trunk up to 40 cm diam at 1.5 m from the ground, rough, red-brown, with raised pustules; slash thick, white-cream, oxidising red-brown or pink.Branches and branchlets curving upwards and terminating in clusters of leaves, developing according to Aubréville's crown model (Tomlinson 1987), that is with 'Terminalia-branching'; leafy branchlets terete, 2-3.5 mm diam, drying dull grey-brown and cracking in oblongs, often covered by crustose lichens; leafscars horseshoe-shaped, pale glossy brown, slightly raised, c. 1 by 1 mm.New shoots probably arising in wet season (June-October), of two types: 1) extension shoots (mainly vegetative, arising laterally from below the established plagiotropic main axes and arching below and then overtopping them; and 2) main shoots, a continuation of the established main axis.

KEY TO THE SPECIES OF AFRICAN TERNSTROEMIA
1 Extension shoots (seen in Tchiengue s.n.collected in May) lack nodes in the proximal 35 -50 mm; the subsequent four internodes are (4-)9-10 mm long, with 1/3 phyllotaxy (each leaf making a third of a circle from the previous).
Vernacular names & Uses -Nkene (Bamumbu language).Medicinally much used (which has possibly contributed to its rarity) by the Mundani people of the Lebialem Highlands, e.g., for sexually transmitted diseases and as a blood tonic (Tacham s.n.), also to address female sterility (Tchiengue s.n.).According to Tacham et al. (2015), who list the species as Ternstroemia sp.nov., Nkene is one of 128 species used by the Mundani: "Decoction of bark is taken with milk for anemia and sickle cell.Concoction with bark of Trichilia is taken orally for pelvic inflammatory disease and infertility".
Conservation -We assess Ternstroemia cameroonensis as Critically Endangered (CR B2ab(iii)+D) according to the categories and criteria of IUCN (2012) since, despite widespread targeted searching over many years, only 10 mature individuals are known to survive (Criterion D).These are all at a single location (area of occupancy estimated as 4 km 2 using the IUCN-preferred grid cells of this dimension) where there are ongoing losses of the habitat due to clearance of natural vegetation for agricultural land in the immediate area (Letouzey 1977, Tchiengue pers. obs. 1999-2015).Trees are known to have been exterminated at the type locality and at Mt Oku in the last few decades resulting in the loss of two of the three known sites for the species.Trees at the only surviving site are also threatened by wounds inflected by harvesting of bark for medicinal purposes.Tacham et al. (2015) report that the species is overexploited for sale locally and in neighbouring markets.No regeneration has been detected at this site (Tchiengue pers.obs.2015), possibly because any seedlings that develop might be swept away by run-off down the steep slopes on which the surviving trees grow.The species has not been cultivated nor seed-banked, although we intend to rectify this.A poster depicting the species, for use in Cameroon promoting its conservation, was produced and distributed by Kew (Cheek 2000a).
Ternstroemia polypetala in the broad sense, including the Cameroon population, as well as those of Tanzania and Malawi, was assessed as Vulnerable by Lovett & Clarke (1998), while it was assessed as Critically Endangered in Cheek et al. 2000: 74.The new species did not feature in the Red Data Book of Cameroon Flowering Plants (Onana & Cheek 2011) since by that time it was recognised to be a separate species but lacked a published name which is required by IUCN before a conservation assessment can be accepted.Ternstroemia cameroonensis (as Ternstroemia sp.nov.sensu Cheek), was listed as Data Deficient (Onana 2013: 208).

Fig. 1
Fig. 1 Ternstroemia cameroonensis.a1.Habit, flowering branches; a2.habit, branch with fruit and flowers; b. female flower opening; c. female flower, side view, 5 sepals, 2 petals and part of the single whorl of staminodes removed to expose the ovary and its basal disc; d. female flower, all perianth lobes and staminodes removed; e. male flower, perianth segments removed; f. innermost petal of female flower showing adnate, flattened staminodes; g. stamen of male flower; h.ovary, apical view, showing 3-lobed, shallowly domed stigma; i. ovary, detail of h.but stigma removed to show the short style; j. fruit (slightly distorted by drying); k. two appressed seeds; l. seed in longitudinal section showing the U-shaped embryo; m. seed, transverse section along lines x-x indicated in l (all: Letouzey 13380, K). -Scale bars: a1+a2 = 5 cm; b -e, j -m = 1 cm; f -i = 1 mm.-Drawn by Andrew Brown.