Rhaphiostylis minima Jongkind ( Icacinaceae ) , a new liana species from Ivory Coast & Liberia

A new species of Rhaphiostylis, R. minima sp. nov. from Liberia and Ivory Coast, is described and illustrated here. It is characterised by its comparatively small size, an ovate to lanceolate leaf blade with long drip tip and a partly glabrous ovary that is in shape in between those of R. elegans Engl. and R. preussii Engl. Rhaphiostylis elegans is lectotypifi ed and illustrated here.

In 2013 a small Rhaphiostylis climber with glabrous leaves and branches was found fl owering and fruiting in the evergreen forest in the south-east of Liberia.With the small and slender leaves with a long drip tip it is already at fi rst sight different from R. preussii.Rhaphiostylis preussii is the only other Rhaphiostylis with glabrous leaves often found in the undergrowth in that forest area.Later it became clear that the shape and indumentum of the ovary is also distinct (Fig. 1F).In Rhaphiostylis the leaf shape and the indumentum of the ovary are important characters for identifi cation of the species (Hepper 1958).The new species, R. minima sp.nov., most resembles R. elegans Engl.from Cameroon, being also a smaller liana with more or less similar leaves.The new species differs from R. elegans by its less stretched and more hairy ovary (Fig. 1F, Table 1).Moreover, there exists also a large geographical gap between the two.The here illustrated fl ower of R. elegans shows the stretched ovary with a long narrow middle part, while the ovaries of the two R. preussii fl owers, from Ivory Coast and Gabon, have only a narrow constriction.The ovary of R. minima sp.nov. is in shape and indumentum in between R. elegans and R. preussii.The ovary of the only other Rhaphiostylis species from Upper Guinea with glabrous leaves and branches, R. beninensis, is in shape and size more or less equal to the one of R. preussii but it is glabrous or almost so (Villiers 1973a: 35).The fl ower of R. preussii, illustrated by Villiers (1973a: 35) after Le Testu 7491 from Gabon, is similar to that of the specimens illustrated here.
The new species is named here R. minima sp.nov., it being the smallest species in the genus.All specimens are small climbers only a few meters high, much smaller than all other Rhaphiostylis species from Upper Guinea.Except for R. preussii, the hairy R. cordifolia is the only other Rhaphiostylis species found in the same evergreen forests.Rhaphiostylis beninensis and R. ferruginea are growing in drier forest types like semi-deciduous forest (Hawthorne & Jongkind 2006: 3).
In a table (Table 1) all Rhaphiostylis species with glabrous leaves and branches from Upper Guinea and R. elegans are compared.
When preparing the Icacinaceae issues of the Floras of Cameroon and Gabon, Villiers could not fi nd type material of R. elegans and could not place it (Villiers 1973a: 41).The original description (Engler 1909: 184) was based on fruiting material only and the fl owers were never described, this made it diffi cult to understand the taxon.In 1986 a duplicate of the destroyed holotype was found in the MO herbarium by Al Gentry and Duncan Thomas (noted on the sheet).During the research on the new species it was possible to match this isotype of R. elegans in herbaria with other specimens.In this publication an illustration is included from a newly identifi ed fl owering specimen (Fig. 1).
In the fresh fl owers of R. preussii and R. beninensis the fl at fi laments touch each other along the edge and together they close around the ovary from their base to about half their length (Figs 2, 3).It is likely that the stamens of R. minima sp.nov.and those of other species in the genus share this character because they also share the special shape of the fi laments.

Materials and Methods
The new species was studied and collected in 2013 and 2014 by the author in the forest in the southeast of Liberia.The BR, K, P and WAG herbaria were searched for additional specimens of the new species and R. elegans.The herbarium, where the specimens are located, is indicated by the international code (herbarium acronym) registered in Index Herbariorum (Thiers continuously updated).Preliminary assessments of the IUCN Red List categories of threat were performed using the IUCN criteria and the Royal Botanic Gardens Kew website http://geocat.kew.org.

Description
Slender woody liana going up to 3-4 m high.Leaves alternate, glabrous; slender petiole 2-3 mm long; blade ovate to lanceolate, 5-10 cm long and 1.5-3.5 cm wide, papery, midrib impressed above, 3 or 4 pairs of main laterals of which the fi rst are often long and ascending, margin entire, base rounded, apex long acuminate, up to 3 cm long with a spathulate tip.Infl orescences fasciculate, supra-axillary with 1-3 fl owers.Flowers bisexual; pedicel 2-4 mm long; calyx 5 lobed, lobes about 1 mm long, puberulous; petals 5, ca. 5 mm long, valvate, free, glabrous.Stamens 5, glabrous; fi laments subulate, gradually narrowing to fi liform above, about 4 mm long, alternipetalous; anthers ca. 1 mm long.Ovary 2.5-3 mm high, hairy on the lower ½ and at the top, almost glabrous on the narrow part in between; style 3.5-4 mm long, excentric but erect.Fruit 2-lobed, fl attened through the longitudinal axis, fl eshy with thin exocarp, smooth and glabrous, but conspicuously hairy on and around the base of the persistent style; endocarp woody, reticulate, about 1.5 cm wide and 1 cm high.

Distribution and habitat
South-east Liberia and south-west Ivory Coast below 250 m altitude.In the shade of evergreen forest with a rainfall of more than 2200 mm a year and a weak dry season.

Conservation status
The "Extent of Occurrence" (EOO) is 6,056 km 2 and the "Area of Occupancy" (AOO) is 32 km 2 , the EOO counts as "Vulnerable" and the EOO counts as "Endangered".The AOO is based on a cell width of 2 km.None of the 9 specimens was collected in a protected area, but it is very likely that the species occurs in Sapo National Park in Liberia, as this protected area is completely included in the species EOO.The plant and its fl owers are not conspicuous, so it is probably more common than what the few collections suggest.However, looking at all the economical development planned and in progress in this   part of Liberia, and while it is not sure that the species grows in a protected area, "Vulnerable" should be the correct status for the moment (B1 & B2 ab(iii), IUCN 2015).

Remarks
All specimens cited under the new species were collected after the publication of the Icacinaceae in the Flora of West Tropical Africa (Hepper 1958).
The leaves of seedlings of Rhaphiostylis beninensis and R. preussii may resemble those of mature R. minima sp.nov.

Remarks
Specimens of Rhaphiostylis elegans key out as R. preussii with the Flore du Gabon (Villiers 1973a) and Flore du Cameroun (Villiers 1973b).According to notes in the WAG herbarium there should be a duplicate specimen of the type in Kew but I could not fi nd it.

Fig. 1 .
Fig. 1.A-C.Rhaphiostylis elegans Engl. A. Flower B. Flower without petals and stamens.C. Leaf.D-G.Rhaphiostylis minima sp.nov.D. Branch with fl owers.E. Flower.F. Flower without petals and stamens.G. Leaf.H-M.Rhaphiostylis preussii Engl.H. Flower.I. Flower without petals and stamens.J. Leaf.K. Flower.L. Flower without petals and stamens.M. Leaf.All fl owers are on the same scale (scale bar with B) and all single leaves too (scale bar with G).A-C from Tchouto & Elad 3310 (WAG), D-G from W.de Wilde 1061 (WAG), H-J from Beentje 1353 B from Ivory Coast (WAG), K-M from Breteler 14204 from Gabon (WAG).Drawn by Hans de Vries.

Fig. 2 .
Fig. 2. Rhaphiostylis preussii Engl.showing fl owers with the fl attened fi laments closing around the ovary while the petals are bending down.Photograph by Ehoarn Bidault (Missouri Botanical Garden) from Bidault 786 (MO) from Gabon.