A new , endangered species of canopy tree from the evergreen forests of Ghana and Liberia , Synsepalum ntimii ( Sapotaceae )

During forest inventories and conservation-orientated botanic surveys in the 1990s, sterile specimens of an unidentifiable woody plant species turned up from several plots in the Wet Evergreen forests (Hall & Swaine 1981) of SW Ghana. The specimens were from ‘hotspot’ forest rich in known, globally rare species (Hawthorne & Abu Juam 1995) and after extensive searches in herbaria in Europe and Ghana, it seems no specimens of the species had been collected before, at least from Africa, showing that even in a relatively well known tropical forest flora like that of Ghana there is much basic inventory and exploration to be done. Eventually, adults were located by Mr. Ntim Gyakari of Ghana Forestry Department, in Ankasa forest (protected as a National Park) and nearby in Cape Three Points Forest Reserve (F.R.). The earlier sterile specimens did prove to be juveniles of a large canopy tree. In 2002 and 2003 fruiting and flowering material was collected from Cape Three Points F.R. One of the areas in Cape Three Points F.R. that includes the new species and many other rarities has become specially protected by the government of Ghana, as a Globally Significant Biodiversity area (GSBA) where no logging or similar disturbance is allowed (Hawthorne & Abu Juam 1995). The discovery is remarkable because Ghana is relatively well sampled compared to many other tropical countries, and new species of large forest tree are discovered infrequently anywhere is Africa. The new species had been overlooked because: it is clearly rare, even locally; deeply fluted, thus of no commercial interest to loggers; it is easily confused with various other Sapotaceae; its flowers are very inconspicuous; and the ripe fruits seem to be soon eaten by animals. Later, in 2012, the species was found in botanic surveys in Liberia: in Sapo National Park (N.P.) by Jongkind et al.; and independently by the author and colleagues in the same year, nearby in the Putu Hills, where seven individuals were recorded, on the slopes and hilltops of Mt Jideh and Mt Montroh, in an area destined to be mined for Iron Ore. The species was included informally in Hawthorne & Jongkind (2006: 108, 109), but is finally described formally here. The new species is typical of tribe Chrysophylleae with five imbricate sepals, five undivided petals, five stamens and an adaxial seed scar; conforming to parts of Synsepalum (DC) Danniell (both taxa here sensu Pennington 1991), with: rotate corolla (Pradosia type flowers, sensu Pennington loc. cit.: 82); spreading corolla lobes far exceeding the tube; exserted stamens fixed at the top of the corolla tube; minute staminodes; no stipules. It differs from species in the closely related genus Englerophytum A.Chev. by: lacking the distinctive closely striate secondary venation of Englerophytum (although the venation is closer to that pattern than all other known Synsepalum species); lack of stipules; and free filaments. As the seed scar covers less than half the surface of the single seed examined, the new species does not key clearly to Synsepalum nor indeed to any genus in Pennington’s key (1991: 182–184), though the presence or absence of endosperm in the seed and the nature of the cotyledons and radicle is not known, the single mature seed having been


INTRODUCTION
During forest inventories and conservation-orientated botanic surveys in the 1990s, sterile specimens of an unidentifiable woody plant species turned up from several plots in the Wet Evergreen forests (Hall & Swaine 1981) of SW Ghana.The specimens were from 'hotspot' forest rich in known, globally rare species (Hawthorne & Abu Juam 1995) and after extensive searches in herbaria in Europe and Ghana, it seems no specimens of the species had been collected before, at least from Africa, showing that even in a relatively well known tropical forest flora like that of Ghana there is much basic inventory and exploration to be done.Eventually, adults were located by Mr. Ntim Gyakari of Ghana Forestry Department, in Ankasa forest (protected as a National Park) and nearby in Cape Three Points Forest Reserve (F.R.).The earlier sterile specimens did prove to be juveniles of a large canopy tree.In 2002 and 2003 fruiting and flowering material was collected from Cape Three Points F.R. One of the areas in Cape Three Points F.R. that includes the new species and many other rarities has become specially protected by the government of Ghana, as a Globally Significant Biodiversity area (GSBA) where no logging or similar disturbance is allowed (Hawthorne & Abu Juam 1995).
The discovery is remarkable because Ghana is relatively well sampled compared to many other tropical countries, and new species of large forest tree are discovered infrequently anywhere is Africa.The new species had been overlooked because: it is clearly rare, even locally; deeply fluted, thus of no commercial interest to loggers; it is easily confused with various other Sapotaceae; its flowers are very inconspicuous; and the ripe fruits seem to be soon eaten by animals.
Later, in 2012, the species was found in botanic surveys in Liberia: in Sapo National Park (N.P.) by Jongkind et al.; and independently by the author and colleagues in the same year, nearby in the Putu Hills, where seven individuals were recorded, on the slopes and hilltops of Mt Jideh and Mt Montroh, in an area destined to be mined for Iron Ore.
The species was included informally in Hawthorne & Jongkind (2006: 108, 109), but is finally described formally here.The new species is typical of tribe Chrysophylleae with five imbricate sepals, five undivided petals, five stamens and an adaxial seed scar; conforming to parts of Synsepalum (DC) Danniell (both taxa here sensu Pennington 1991), with: rotate corolla (Pradosia type flowers, sensu Pennington loc.cit.: 82); spreading corolla lobes far exceeding the tube; exserted stamens fixed at the top of the corolla tube; minute staminodes; no stipules.It differs from species in the closely related genus Englerophytum A.Chev.by: lacking the distinctive closely striate secondary venation of Englerophytum (although the venation is closer to that pattern than all other known Synsepalum species); lack of stipules; and free filaments.As the seed scar covers less than half the surface of the single seed examined, the new species does not key clearly to Synsepalum nor indeed to any genus in Pennington's key (1991: 182-184), though the presence or absence of endosperm in the seed and the nature of the cotyledons and radicle is not known, the single mature seed having been Pl.Ecol. Evol. 147 (1), 2014 left intact.It is, however, most similar to species previously placed in Afrosersalisia (now Synsepalum) and I am grateful to Dr. T. Pennington (Royal Botanic Gardens Kew, pers. comm.) for confirming its placement in Synsepalum.

MATERIALS AND METHODS
Specimens (normally sterile) associated with Rapid Botanic Survey (RBS) originally alerted the author to the new species.Orthodox herbarium collections were made when fertile individuals were found.Older specimens, either unidentified or previously named, were sought across potential genera in herbaria (GC, FHO, K, WAG) and online via JSTOR Global Plants (http://plants.jstor.org);however no existing unidentified or misidentified specimens amongst other species were found in the herbaria.The fertile types have been distributed to several herbaria.Photographs taken during the collection of the type specimen have proved useful for adding to the description, and for publicising the new species for conservation purposes.In 2013, known localities in Ghana were revisited and leaf specimens collected both as orthodox herbarium collections and fragments were placed directly in silica gel for DNA analysis (marked as '(DNA sample)' with the cited specimens below) .A large tree most similar to Synsepalum afzelii (Engler) Pennington and S. cerasiferum (Welw.)Pennington (both previously in Afrosersalisia A.Chev.).Differing from both in the glabrous ovary (vs.covered in dense, c. 1 mm long, appressed orange-brown hairs in S. afzelii and S. cerasifera); shorter pedicels (0-1 mm long in S. ntimii; 1-8 mm in S. afzelii and S. cerasifera).S. ntimii also differs in leaf venation: the 11-19 pairs prominent lateral nerves are interspersed with equally prominent reticulate venation prominent below, with many of these second and third order veins tending to run parallel to the main laterals; whereas both S. afzelii and S. cerasifera lack prominent finer reticulations below, and there is a clear distinction between the 9-16 prominent lateral nerves and obscure, scalariform or impressed finer venation below.-Type: Ghana, Western Region, Cape Three Points Forest Reserve, hills in NE, alt.50 m, 23 Feb. 2003, Hawthorne & Gyakari 203a024 (holo-: FHO; iso-: BR, GC, K, MO, P, WAG).
Tree to 35m tall.Bole to c. 50 cm diameter above buttresses, deeply fluted up to main branches (fig.1), flutes merging with edges of the tall, straight or concave-edged buttresses, with basal diameter across the widest buttresses 3-5 times the diameter above buttresses, and up to c. 2 m DBH (including flutes and buttresses) (fig.3A).Bark grey to reddish or orange-brown, rough and flaky in parts or rather smooth, with raised, horizontal fine (c. 2 mm) ridges or hoops on smoother parts; with occasional horizontal ridges or 10-20 cm knee-like bosses; bark slash reddish-orange, fibrous, thin, with abundant white latex.Branchlets with leaves clustered towards tips (fig.3C-D); Aubréville's architectural model (Hallé et al. 1978); apical bud and youngest internode appressed pubescent, soon glabrous; without obvious stipules, even in the apical bud.Older branchlets, slightly rugose, with numerous elliptic lenticels; old fertile branches covered with many small 1 mm knobs at old nodes where flowers are clustered or have fallen.Leaves alternate, spirally arranged, oblanceolate to obovate, occasionally elliptic, apex acuminate with rounded acumen tip, or (especially on flowering shoots) apex fully rounded, without acumen, and/or emarginate; leaf base decurrent with c. 1 cm of basal section of lamina < 3 mm wide on larger leaves.Petiole (below decurrent section of lamina) 0-9 mm long, appressed puberulous at first, soon glabrous.Lamina (including narrow, decurrent section above petiole) 6.5-13 × 2.0-5.0 cm on fertile specimens, up to 22 × 9 cm in shade leaves and saplings; length/width ratio 2.2-3.2;coriaceous, glabrous or with few minute appressed hairs when developing; margin thickened, slightly recurved near base on dried leaves.Midrib prominent on both surfaces, but the prominent midrib sometimes impressed within a channel above.Lateral nerves: 11-19 pairs main secondary nerves directly joining a loopy sub-marginal nerve 1-3 mm from margin, but with intermediate densely reticulate secondary and tertiary nerves similarly thick and prominent below, leaving little space for fourth order or finer venation, and often aligned and suggesting > 19 parallel lateral nerves at arm's length.Secondary and finer venation above sometimes finely channelled.Flow- ers in fascicles, forming a dense brush along branchlets on old nodes immediately below current leaves, with occasional flowers in axils of current leaves (fig.3C-F); sessile to sub-sessile, pedicels 0-1 mm long; smelling of rancid hay or fermented cocoa-waste.Calyx with 5 sepals imbricate (quincuncial) even in fruit, c. 1.5 mm long; very short tube or connate section c. 0.5 mm long at base, lobes broadly ovate to orbicular, c. 1-1.5 mm long × 1-1.5 mm wide, appressed puberulous on outer surface.Corolla rotate, with 5 petals imbricate in bud, 4-5 mm diameter when open; connate basal section (short tube) 0.2 mm; lobes rounded or abruptly acute at apex, 2.5 long × 1.2-2 mm wide, becoming recurved, yellow, soon falling and abundant on ground below flowering trees (fig.4A-D).Stamens five, 2.25-2.5 mm long; filaments joined to base of corolla lobes at mouth of tube, c 1.5 mm long; anthers broadly ovate and deeply cordate, extrorse, c. 1 mm long × 1 mm wide at base.Staminodes rudimentary, between corolla lobes, variable in form, acute, ligulate or three-lobed, c. 0.2 mm long × 1 mm wide; corolla soon falling to leave ovary tightly wrapped in imbricate calyx with apical portion and style emerging.Style 0.5-1 mm long, unlobed; ovary hemispherical, c. 1 mm radius, five-locular, glabrous, but with membranaceous, darker coloured nectary disc surrounding the lower half, the disc obscurely divided into c.sixteen ligulate lobes, bathed in copious nectar.Fruit an ellipsoid berry with a fleshy to soft-leathery pericarp, 3.5 × 1.5 cm, one-seeded, dark reddish, drying black.Seed (single undissected specimen possibly immature) ellipsoid 15 mm long × 7 mm wide, flattened on adaxial face, yellow to orange-red, slightly shiny with rough 10 × 1.5 mm scar along adaxial edge.Habitat and distribution -A canopy tree on well-drained ridges and slopes (alt.50 m) in Wet Evergreen Forest (sensu Hall & Swaine 1981) of SW Ghana; and in similar evergreen forest (200-600 m) in the Putu Hills and Sapo NP, SE Liberia (fig.4E).The saplings, to 2 m at least, are shade-tolerant, occurring in the deepest understorey shade.The species is to be expected in the same Wet Evergreen forest type, nearby in SW and SE Ivory Coast.Phenology -Flowers in February (near end of dry season); ripe fruits in June (rainy season).Field Notes -Saplings and young, sterile trees of S. ntimii can be confused with various other Sapotaceae which grow in the same forest and have similar bark and clustered leaves, Terminalia-style branching and latex (Hawthorne & Gyakari 2006: 64-79), including: Neolemonierra clitandrifolia (A.Chev.)Heine, which however has distinctive venation (see Hawthorne & Jongkind 2006); and especially Synsepalum afzelii (Engl.)T.D.Penn.The latter has subtly different, generally smaller, less acuminate leaves, a more brittle, plastic-like texture and less apparent venation; and usually has a bright red flush of new leaves (fig.5D-E) not seen in S. ntimii (fig.5F).Mature trees of S. ntimii are strikingly fluted (fig.1), more so than these other species (fig.5B-C), though the buttresses are similar (figs 3A-B, 5A).Conservation Status -The species is legally protected in Ghana, both by virtue of it being classified as a Black Star Species and by occurring in protected areas ('GSBAs'), set up with selected Forest Reserves on the basis of high concentrations of such species (Hawthorne & Abu Juam 1995).In spite of having a high Extent of Occurrence (33,166 km 2 ), from Ghana to Liberia, It qualifies as Endangered in the IUCN system (IUCN, 2001) by virtue of having a low Area of occupancy (AOO = 28 km 2 , measured at 2 km resolution); and by having a rather low population density in localities where it is known.The Putu Hills population in Liberia, where it is more common than in its other known localities, is liable to be seriously diminished by mining in the coming decade.The survey there was an Environmental Impact assessment prior to mining, though a third of the Putu Hills records were from sample areas outside of any proposed mine footprint.Etymology -Named after former curator of the Forestry Herbarium, Kumasi, Ghana, fellow dendrophile, and herbalist and field botanist extraordinaire, Mr. Ntim Gyakari (fig.3B).

CONCLUSION
The recognition of this species as new, and within the current circumscription of Synsepalum, is confirmed at the time of submission of this paper by a phylogenetic study of Synsepalum and Englerophytum (Borg 2013, B. Mackinder, Royal Botanic Gardens Edinburgh, pers. comm.).The new species extends slightly the limits of Synsepalum, already a heterogeneous genus after the sinking of genera such as Afrosersalisia by Pennington, and the new species is perhaps closer to Englerophytum than other species in the genus.
The Ghanaian government has done much to conserve the local hotspots in which this and other rarities survive, and at the other end of its range, Sapo N.P. in Liberia should provide another refuge, though only one tree has been reported from Sapo and the generally low population densities of S. ntimii and increasing pressure from mines, logging and farms in the surrounding landscape are a serious concern.

Figure 4 -
Figure 4 -Synsepalum ntimii: A, detail of flower with nectar (bottom right); B, detail of ovary, girdled by brown membranaceous disc; C, fallen corolla from forest floor; D, fallen corolla, lateral view showing extrorse stamen; E distribution map, with arrows indicating the two regions in which the species is known, black circles showing specimen localities.Fully protected areas and forest reserves are shown in green (source UNEP/WCMC http://www.protectedplanet.net),accounting for most of the remaining forest.A-D from Hawthorne & Gyakari 203A024 (FHO).Photographs by W.D. Hawthorne.