Hymenostegia viridiflora Mackinder & Wieringa, 2013

Hymenostegia viridiflora Mackinder & Wieringa View in CoL , sp. nov. — Fig. 1 View Fig , 2 View Fig ; Map 1 View Map 1

Diagnosis: Most closely resembling H. floribunda Harms but differing in several aspects including the colour of the petals which are pale green to greenish yellow (not lemon yellow); bracteoles which have 9–15 (not 5 or less) palmate dark veins from base and the part of the stipule above the point of

3 mm attachment which is narrowly oblong, four to five times longer than wide (not linear to filiform, six to nine times longer than wide).

Type. van der Burgt 568 (holo WAG; iso BR, C, G, K, MA, MO, NY, PRE, S, SCA,US, W, YA), Cameroon, South-West Province, Korup National Park , Science camp near P transect, tree above the kitchen, N5°01', E8°48', fl. 4 Jan. 2000 GoogleMaps .

Etymology. The species epithet refers to the conspicuous pale green to greenish yellow petals,a colour which to our knowledge has not been recorded in any other species of Hymenostegia . Other Hymenostegia species have lemon yellow petals.

Tree to 38 m tall, dbh 50–106 cm; bole straight, somewhat fluted up to 2.5 m height, buttresses of several dm height extending to 5 m from the base of the tree, bark smooth. Twigs pale brown sericeous when young, glabrescent; hairs up to 2 mm long. Bud scales 5–6, caducous, distichous, proximal scale sub- orbicular, c. 2 mm diam, brown, coriaceous, not keeled, outer and inner surface glabrous except along the lower margins, the indumentum often hidden under the next overlapping scales, distal scales becoming progressively longer and relatively narrower, apical scale ovate, c. 6.5 by 4 mm, not keeled. Stipules in pairs, free, seen in young foliage but then falling, auriculate at base, the auricle suborbicular, 3.5–9 mm across, 1.5–5 mm from point of attachment to base, outer surface appressed pubescent, inner surface glabrous, margins ciliate, upper part of stipule oblong, 10–20 by 2.5–5 mm, outer surface pubes- cence (if present) confined to a central longitudinal band of appressed hairs, margins ciliate, inner surface glabrous, apex acute. Leaves 1 paripinnate, dark green and slightly glossy,

1 Leaf and leaflet measurements were taken from mature leaves but not from those within the inflorescence.

mature leaves 7–16.5 by 3.8–8.1 cm, about 2–3 times longer than wide; petiole 1–3(–7) mm long, rachis 5.6–12.2 cm long, channelled, glabrous or sparsely to moderately pubescent. Leaflets sessile in (4–)6–10 pairs, upper and middle leaflet pairs opposite, lower 2 –3 pairs subopposite, largest leaflets usually the middle pair; largest leaflet 21–39 by 7–18 mm, 2–4 times longer than wide, usually oblong but sometimes becoming slightly wider in distal half, base asymmetric, proximal margin curving outwards towards the apex into an auricle, lower surface appearing glabrous with a hand lens (20 × magnification) but sparse appressed puberulous indumentum visible under a microscope, mid-vein sometimes pubescent, particularly in young foliage, fringing hairs c. 0.75 mm long, present particu- larly on the lower margins of young leaflets but sometimes absent in mature foliage; mid-vein central, prominent above and below for most of its length, becoming obscure just before the apex. Inflorescence a 10–26-flowered raceme, usually held erect, axis 3.8–13.5 cm long, including a peduncle 4–9 mm long with a moderate to dense indumentum of golden spreading hairs c. 1.25 mm long. Floral bracts ovate, 5–8 by 1.5–4 mm, becoming smaller towards the apex of the inflorescence, inside glabrous, outside glabrous except for some hairs in the basal half sometimes confined to a patch just at the base, margins ciliate, hairs 0.5 mm long. Pedicels: portion of pedicel below bracteoles 6–10.5 mm long, hairs 0.5–1.5 mm long. Bracteoles opposite, ovate to obovate, 8.5–9.5 by 7–8.5 mm, with 9–15 reddish palmate veins emerging from the base, portion of the pedicels above the bracteoles 0.5–1 mm long, glabrous or with a few scattered hairs. Hypanthium 3– 4 mm long, glabrous inside and out. Sepals 4, white with greenish and reddish lines, somewhat cucullate, reflexed or spreading, the adaxial sepal more belatedly so than the others, outside glabrous, inside basal half with an ovate hairy patch of erect hairs 0.7 mm long, apical margin with a few short hairs c. 0.1 mm long, adaxial sepals 5–6 by 5–6 mm, lateral sepals 3.5–6 by 3–4 mm, abaxial sepals 5–6 by 3–4 mm. Petals 5 of which 3 large, pale green to greenish yellow, adaxial petals narrowly spathulate, 8–11 by 1.5–3 mm, lateral petals narrowly spathu- late 8–12 by 1.7–4 mm, abaxial petals inconspicuous, linear, 2–3 by 0.1–0.3 mm. Stamens 10, filaments 9–17 mm long, white, anthers 1.2–1.4 mm long, yellow, slits with red margins. Ovary stipe 3.5–4.5 mm long, glabrous at base only, otherwise densely woolly, ovary 4–4.5 by 2 mm, glabrous faces, sutures densely woolly, ovules 1–2. Pods held just above the crown leaves, compressed, 7.1–8 by 3.3–3.9 cm at broadest part, triangular, broadest towards apex, upper suture not broadened, valve surface glabrous, immature pods with 10–14 conspicuous, fine, lateral nerves, not visible on mature pods, beak 3–5 mm long; single developed seed, discoid, 22– 31 by 13– 23 by 4–6 mm when fresh. Seedlings : hypocotyl 5.5–7.8 cm long, glabrous to sparsely pubescent, epicotyl 7–11 cm long, spreading pubescent, cotyledons suborbicular, c. 16 by 15 mm, leaves first pair opposite, then all alternate, 8.3–11 by 4.2–5.4 cm; leaflets sessile, in 6–8 pairs, opposite, largest leaflet at the middle of the leaf, 23–28 by 8–10 mm.

Distribution & Ecology — Cameroon, SW and Littoral Prov- inces. Primary and little disturbed lowland forest, along river banks; 50– 100 m.

Additional specimens examined. Both confirmed (flowering) and unconfirmed (fruiting or sterile) records are included here and plotted on the distribution map to aid in the discussion of conservation status.

Confirmed records (paratypes). CAMEROON, Littoral, Letouzey, R. 11088 ( MA, MO, P, WAG), près Nkam , 10 km NNE de Ngambe (feuille IGN 1/200.000 Ndikinimeki), N4°17', E10°38', 24 Jan. 1972 (fl). South-West Province, Burgt, X. M. van der 568 ( G, K, S, SCA, WAG, YA), Korup National Park , Science Camp near P transect,tree above the kitchen, N5°01', E8°48', alt. 100 m, 4 Jan. 2000 (fl); Burgt, X. M. van der 597 ( G, SCA, WAG), Korup National Park , road to Isangele, N4°58', E8°48', alt. 50 m, 26 Feb.2000 (st); Burgt, X. M.van der 598 ( G, S, SCA, WAG, YA), Korup National Park , Science Camp near P transect, tree above the kitchen, N5°01', E8°48', alt. 100 m, 11 Mar.2000 (fr); Burgt, X. M.van der 605 ( G, SCA, WAG), Korup National Park , Science Camp near P transect, tree above the kitchen, N5°01', E8°48', alt. 100 m, 2 June 2000 (fr); Burgt, X. M. van der 621 ( P, WAG), Korup National Park , Science Camp near P transect,tree above the kitchen, N5°01', E8°48', alt. 100 m, 2 Nov. 2000 (st); Pearce , L. J. 11 ( BR, G, K, MO, P, SCA, US, W, WAG, YA) GoogleMaps , Korup National Park, North of P transect,NW plot,subplot 43 XN, N5°01', E8°47', alt. 100 m, 24 Feb. 2008 (fl) GoogleMaps .

Unconfirmed records. CAMEROON, Central Province, Letouzey, R. 11626 (K, P), 20 km NW Yaoundé, Mbam Menkoum massif, c. N3°57', E11°24', 18 Aug. 1972 (fr); Letouzey, R. 12253 (BR, P), 40 km NNE Eseka, inselberg W of Botmakak, c. N4°00', E10°54', 7 Dec. 1973 (st). South Province, McKey, D.B. C91/25/41 (K),Campo Forest Reserve, 20 km ENE of Ebodie,c. N2°38', E9°59', 1 Oct. 1991 (st); Parren, M.P.E. 56 (KRIBI, WAG), Ebom, N3°07', E10°46', alt. 400 m, 1 Mar. 1997 (fl); Shu Neba, G.X. 4969 (WAG), Mvila, Ebom, Minwo catchment, TCP, Ecoll 1, plot M34, N3°07.2', E10°44.5', alt. 425 m, 3 July 1999 (st); Shu Neba, G.X. 5140 (WAG), Mvila, Ebom, Minwo catchment, TCP, Ecoll 1, plot M32, N3°07.4', E10°44.3', alt. 450 m, 10 Aug. 1999 (st); Wilde, J.J.F.E. de 12078 (KRIBI,WAG), Minwo-Area (D2), between Mekalat and Lolodorf, N3°06.8', E10°45.1', alt. 470 m, 4 Dec. 1998 (st). South-West Province, Thomas , D.W. 8237 (MO), Banyu last moto, between Sekim and Banyu, N5°10', E9°14', alt. 400 m, 25 Apr. 1988 (st); Cheek, M.R. 8271 (K, YA), Ndian, Ekundu Kundu, transect 9, between km 4 & 6, along E-W river, N5°07', E8°51', alt. 170 m, 29 Apr. 1996 (st).

Conservation assessment — Hymenostegia viridiflora is assessed here as Vulnerable VU B1ab(i,iv) according to the criteria of IUCN (2001). In IUCN terms, we consider the status of VU as a best estimate given that the assessment was not straightforward and that there is more than one plausible category to which the species might be assigned. The category proposed is based on confirmed (flowering) records from sub- populations into two locations, one in Korup National Park in SW Cameroon and the other near Nkam in the Littoral Province (denoted as closed dots on Map 1 View Map 1 ). From these records, we calculate a species EOO of 570 km 2 suggesting a category of Endangered and AOO of 1 460 km 2 (at cell size 22 km 2) sug- gesting VU. We have selected the lower category because the SW province population occurs in Korup National Park, a protected area where other than stochastic events, no other threats are known. We are also influenced away from Endan- gered (E) and towards VU by the several unconfirmed records of the species (sterile or fruiting only collections) which were they confirmed, would result in a designation of Least Concern (LC). However, until we are able to confirm those records we do not consider LC, which is a category that also accommodates pantropical weeds, as an appropriate conservation status for this relatively poorly known species from the Cameroonian forest, a forest that is under considerable threat. We also considered the category of Data Deficient (DD) which is intended for species for which data are inadequate to determine a threat category with confidence. However, we judge that there exists sufficient data to arrive at an assessment, based on the combination of our current understanding of species distribution and knowledge of general levels of threat to forest habitats in Cameroon.

Notes — In the field flowers were noted as weakly scented (van der Burgt 568) or sweetly and strongly scented (L.J. Pearce 11). A colour change in the petals of fallen flowers was also observed in the field (van der Burgt 568) who recorded the fallen petals as ‘dark red inside’ and ‘dirty white outside’. About 10 weeks is needed for flowers to develop into almost mature pods (van der Burgt 598). Once mature, pods audibly dehisce whilst still on the tree and the seeds are dispersed up to 18 m from the edge of the crown (van der Burgt 621). Following dehiscence the valves do not remain on the tree but fall to the forest floor (van der Burgt 621).

Letouzey 11626 (K, P) collected in Cameroon’s Central Prov- ince, 20 km NW Yaoundé on the Mbam Menkoum Massif consists of a vegetative collection mounted on the herbarium sheet with associated pods gathered from the forest floor in a capsule. The pods are hairy with a winged upper suture. Typi- cally, pods of Hymenostegia s.str. species are glabrous without a winged upper suture. We suggest that Letouzey 11626 may represent a mixed collection with only the foliage belonging to H. viridiflora . We speculate that the pods gathered from the forest floor are a collection of Talbotiella breteleri (Aubrév.) Mackinder & Wieringa ( Mackinder et al. 2011) based on the combination of the pod morphology (indicating the genus Talbotiella ) and the collecting locality which is the same as that of a known sterile collection of T. breteleri, Letouzey 11635 (YA). No other species of Talbotiella are known from the vicinity.