Ternstroemia guineensis (Ternstroemiaceae), a new endangered cloudforest shrub with neotropical affinities from Kounounkan, Guinea, W Africa

Ternstroemia guineensis is described from a sandstone table mountain at Kounounkan, possibly the last in the Fouta Djallon (Guinea Highlands) to remain largely unimpacted by humans and to have mainly intact natural habitats. It occurs about 2400 km westward of the nearest existing record (Nigeria) of the genus in Africa. It is confined to cloud (submontane) forest in galleries along watercourses. Its conservation status is assessed as Endangered using the IUCN 2012 criteria. The species differs from the other two African highland species, T. cameroonensis and T. polypetala, in having hermaphrodite flowers with a long subcylindric style and punctiform stigmas, and petals connate at the base into a tube (not dioecious, with a short style and cone-like stigmas, and free petals) resembling in these features the neotropical Ternstroemia species, as does also the lowland wetland T. africana of Nigeria, Gabon and Angola.


Introduction
In November 2017, the last three authors were on a botanical survey team seeking to discover the most important surviving areas for plant conservation in Guinea following the criteria of Darbyshire & al. (2017) and Darbyshire (2019+). The object is to evidence Important Plant Areas and to prioritize them for protection. The November 2017 survey was at Kounounkan Forest Reserve, the largest surviving remnant of forest in Fouta Djallon. Among the herbarium specimens collected was one, Pepe Haba 1060, which was identified as a Ternstroemia Mutis ex L. f. This specimen was collected about 2400 km westward of the nearest existing record of the genus in Africa. It is superficially similar to the recently described T. cameroonensis ) of Cam-eroon to the east. Close inspection showed it to be different from all other species of the genus known in Africa by the absence of any visible secondary nerves and from the other African highland species in the leaves arranged in pseudo-verticils and lacking Terminalia-branching. Rehydration and dissection of the flowers showed further points of difference (see Table 1). Attempts were made to key out the specimen in the three regional treatments of Ternstroemia for the Neotropics (Kobuski 1942a(Kobuski , 1942b(Kobuski , 1943 and it was compared with material of neotropical species at Kew, but no match was found. Accordingly, it is described in this paper as T. guineensis Cheek, sp. nov. Additional specimens with fruit developed were collected on a follow-up visit by the three last authors in February 2019, and ripe fruit were observed and seed collected (Konomou 691) in May 2019. 352 Cheek & al.: Ternstroemia guineensis from Guinea

Ternstroemia
The genus Ternstroemia is pantropical, extending into subtropical and temperate areas (Stevens 2001+;Weitzman & al. 2004). Estimates of species numbers range from c. 100 (Stevens 2001+) to 152 (Plants of the World Online 2018+). Of these 152 species, 101 are Neotropical, just three African, with 31 in Malesia (SE Asia), one (T. cherryi (F. M. Bailey) Merr. ex J. F. Bailey & C. T. White) extending to N Australia, with 15 species in China, Indo-China, Japan and Tibet, and one species, T. gym nanthera (Wight & Arn.) Bedd., extending to India. The genus is absent from Madagascar, the Indian Ocean, all but W Oceania, and from N temperate areas apart from China and Japan. Most of the species are montane and submontane and are absent from lowland habitats apart from some species in swamp forest. The genus is incompletely known, especially in the neotropics: in local Floras, species remain formally unnamed, for example in the Venezuelan Guayana (Berry & Weitzman 2005) and in Guaramacal (Venezuelan Andes) (Dorr & al. 2000: 144).
The number of species described as new to science each year regularly exceeds 2000, adding to the estimated 369 000 already known (Nic Lughadha & al. 2016), although the number of flowering plant species known to science is disputed ). Only about 7 % of plant species have been assessed and included on the Red List using the IUCN (2012) standard (Bachman & al. 2019), but this number rises to 21 -26 % when additional evidence-based assessments are considered, and 30 -44 % of these assess the species as threatened (Bachman & al. 2018). Newly discovered species such as that reported in this paper are likely to be threatened, since widespread species tend to have been already discovered. There are notable exceptions to this rule (e.g.

Vepris occidentalis
Cheek (Cheek & al. 2019) a species widespread in W Africa from Guinea to Ghana). Generally, it is the more localized, rarer species that remain undiscovered. This makes it all the more urgent to discover, document and protect such species before they become extinct or possibly extinct e.g. as is Inversodicraea pygmaea G. Taylor in Guinea (Cheek 2018;Couch & al. 2019), or in the case of another cloud forest tree Vepris bali Cheek (Cheek & al. 2018a).

Material and methods
All specimens cited have been seen by the authors. Herbarium citations follow Index herbariorum (Thiers 2019+), the International Code of Nomenclature for algae, fungi, and plants (Turland & al. 2018) and the International Plant Names Index (IPNI 2019+). 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.
Phenology -flowering in the dry season from November onward, a few flowers still present in February, when fruits are nearly fully-formed. Fruits ripe in May, as wet season begins. Shoot extension and new leaves are inferred to develop in the wet season (May-October).
Distribution -Ternstroemia guineensis is currently only known from the southernmost plateau of the Kounounkan Massif in Forécariah Prefecture, an uninhabited sandstone table mountain, where it is known from gallery forests along four streams.
Ecology -The species was found in species-rich submontane gallery (cloud) forest, on rocky soils, at 900 -1100 m altitude.
Conservation status -Ternstroemia guineensis is a very rare species, collected only by the last three authors, on a single uninhabited table mountain despite targeted searches on other mountains over three years by our team. We assess T. guineensis as Endangered (EN B1+B2ab(ii,iii,v); D) according to the categories and criteria of IUCN (2012) since the species has only been found at the one location, where 169 mature individuals have been observed. The grasslands on parts of the nearby main southern plateau of the Kounounkan Massif are frequently burned in the dry season. These frequent dry-season fires may damage gallery forest edges; the habitat of T. guineensis. Continuous decline was observed there in quality of habitat, in the form of burned and fire-killed trees of other species, and continuous decline in number of mature individuals of T. guineensis is therefore likely should these frequent fires reach the location of that species.
The species is known from a total of nine sites (four collections and five observations) at one location. The area of occupancy is 16 km 2 , calculated using IUCNpreferred 2 × 2 km cells, and the extent of occurrence slightly larger, estimated at 17 km 2 to satisfy IUCN preferences, although a minimum convex polygon around the nine sites gives an area of only 4.3 km 2 . Despite searches elsewhere in Guinea, especially in the Kounounkan Massif, the species has not yet been found outside the nine known sites. It has been conjectured that Ternstroemia guineensis and other point endemics that occur at the same location (e.g. Gladiolus mariae Burgt, Burgt & al. 2019), several of which are also in the process of being described, may be relics, and may once have been much more widespread over the sandstone table mountains of the Fouta Djallon, since these appear so similar in terms of ecology to the Ternstroemia location, excepting the presence of humans and the consequent high fire-frequency (Burgt & Haba cited in Couch & al. 2019).
Although the location is unprotected, the immediate threat of farmers or cattle rangers moving in is currently low, due to its inaccessibility. However, this could change rapidly. Currently, there are no paths up to and on the southern plateau. Should a path to the site be constructed, there is a risk that, as with other sandstone table mountains known to us in Guinea, livestock will be introduced for seasonal grazing and as a consequence dry-season fires will be introduced, and as a result submontane gallery forest will be degraded and will decrease in extent. In this event, the assessment should be reviewed and it is likely to become Critically Endangered.
The authors intend to raise public awareness through a poster programme on the importance of protecting this rare species and its habitat, and efforts are being made to obtain seed for seed banking as a safeguard, and to continue to attempt to discover additional locations for Ternstroemia guineensis. Given the comparatively large number of rare plant species recorded at the site for this species, and the presence of priority threatened habitats ( sandstone cliffs, high altitude bowal, submontane and lowland evergreen forest) the location for T. guineensis has been included in the proposed Kounounkan Important Plant Area, for which National Park status is being sought (Couch & al. 2019).

Morphological affinities and amphi-Atlantic distributions
The morphological affinities of Ternstroemia guineen sis are not with the other highland African Ternstroemia species, T. polypetala Melch. and T. cameroonensis. The last two species both have 7 or more free petals and minute styles bearing large, foliose stigmas that form a cone over the top of the ovary. In contrast, T. guineensis and the lowland swamp-dwelling T. africana Melchior both have hermaphrodite flowers with 5 petals united at the base, and a cylindric style that exceeds or equals the ovary in length, bearing two minute, punctiform stigmas. The features of T. guineensis and T. africana are seen in the Neotropical Ternstroemia treated by Kobuski (1942aKobuski ( , 1942bKobuski ( , 1943, while the affinities of T. polypetala (and T. cameroonensis) are with the Asian species (e.g. Kobuski 1961). It can be postulated that the ancestors or ancestor of T. guineensis and T. africana arrived in W Africa as a result of long-distance dispersal from the Neotropics as did Pitcairnia feliciana (A. Chev.) Harms & Mildbr.
(Bromeliaceae) and Maschalocephalus dinklagei Gilg & K. Schum. (Rapataceae) shown e.g. by Givnish & al. (2004). In the case of the Pitcairnia and Maschaloce phalus, the direction of travel was unambiguously from west to east, since all other members of their families are Neotropical. However, this is not the case with pantropical Ternstroemia. Although the species diversity of the genus in the Neotropics, with 101 species, far exceeds that of Africa, now with four species, it cannot be ruled out that the Neotropical Ternstroemia may have arisen by dispersal from Africa. In fact, although Africa has by far the lowest species diversity of Ternstroemia of all the three major tropical areas, it has the highest level of infra-generic diversity for Ternstroemia, containing species with both Asiatic (T. polypetala and T. cameroonensis) and American (T. africana and T. guineensis) morphology. It is even possible that Africa was the crucible in which Ternstroemia arose. This hypothesis is supported by the proximity of potential sister genera Visnea (Macaronesia) and Balthasaria (Albertine Rift and Eastern Arc mountains).
Another group recently discovered to be amphi-atlantic is Peridiscaceae, regarded as American until research showing that Cameroonian Medusandra Brenan together with WC African Soyauxia Oliv., is confamilial (Soltis & al. 2007;Breteler & al. 2015). In this case also, travel from east to west is credible. Morphological and species diversity in Peridiscaceae is far higher in Africa than in the Americas.

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Cheek & al.: Ternstroemia guineensis from Guinea ment Food and Rural Affairs (DEFRA), UK government (project Ref. 23 -002, 2016(project Ref. 23 -002, -2019 and by the Ellis Goodman Family Foundation. This supports Kew's Tropical Important Plant Areas (TIPAs) science strategic output. The Garfield Weston Foundation funded the "Global Tree Seed Bank Project" of Kew's Millennium Seed Bank Partnership, enabling five expeditions to Guinea to support the collecting of seeds of numerous rare trees and shrubs, including those in the Kounounkan Massif, as well as in the discovery of some new plant species such as this Ternstroe mia. Janis Shillito is thanked for typing the manuscript. Ib Friis (C) and an anonymous reviewer are thanked for constructive comments on an earlier draft of this paper.