Mischogyne gabonensis (Le Thomas) Gosline, 2019

Gosline, George, Marshall, Andrew R. & Larridon, Isabel, 2019, Revision and new species of the African genus Mischogyne (Annonaceae), Kew Bulletin 74 (28), pp. 1-23 : 13-14

3. Mischogyne gabonensis (Le Thomas) Gosline comb. et stat. nov.

http://www.ipni.org/urn:lsid:ipni.org:names:60478275-2

Mischogyne elliotiana (Engl. & Diels) Le Thomas var. gabonensis Pellegr. ex Le Thomas, Flore du Gabon 16: 291 (1969). Uoariastrum elliotianum var. gabonensis Pellegr. ( Pellegrin 1949) , nom. nud. Type: Gabon, Mayumba, region de Nyanga, 26 Aug. 1914, Le Testu 1768 (hololectotype P, sheet here designated [P00315820]; isotypes BM! [BM000547338], BR × 2* [BR0000008801661, BR0000008802330], LISC* [LISC000379], P × 2* [P00315817, P00315818], W A G × 5 * [W A G0 1 7 5 0 9 8, W A G 0 1 7 5 0 9 9, WAG0247284, WAG0247285, WAG0247286]).

Tree 3 – 7 (– 25) m tall, up to 25 cm in diam., branches and twigs glabrous. Taeigs light grey to brown, striate. Shoot buds with light brown hairs 0.05 – 0.1 mm long. Petioles 5 – 10 mm long, 1.5 – 2 mm in diam., sparse indumentum of hairs 0.1 mm long or glabrous. Leaf lamina obovate, 8 – 16 cm long, 4 – 7 cm wide, length:width ratio 2 – 2.5, apex rounded, abruptly acuminate, acumen linear, 1 – 3 cm long, 0.5 – 1 cm wide at base, 0.2 – 0.4 at mid-length, base cuneate, coriaceous, glabrous on both sides, glossy green above and light green below when fresh, drying matte, olive to brown, lighter below; midrib glabrous above and below; secondary veins 6 – 9, ascendant at 30° – 50° from midrib to 20 – 40% of length of the leaf, anastomosing near margin. Floaeers with flower buds 0.7 – 1.3 cm long, 0.3 – 0.5 cm in diam. Pedicel 0.5 – 1.2 cm long, 0.3 – 0.9 mm in diam., pubescent, hairs 0.1 – 0.3 mm long, appressed, light brown. Sepals united into a thin membranous capsule, ovoid to conical, 0.7 – 1.3 cm long, 0.3 – 0.5 cm wide, length:width ratio 2 – 2.5, base rounded, apex acute or caudate ( Fig. 2D ). Calyx opens by rupturing, usually, into two parts drying dark brown, tomentose outside and inside, often the tips are lost leaving truncate “sepals”, thin, fragile and caducous. Petals narrowly elliptic, 1.4 – 1.6 cm long, 0.3 – 0.5 cm wide, length:width ratio 3 – 3.5, base truncate, apex acute, outer surface densely pubescent, hairs 0.1 – 0.3 mm long, appressed, light brown, inner surface tomentose becoming glabrous, white when fresh, inner surface dark brown in herbarium material. Torus truncated conical, 2.2 – 3 mm. long, 1.5 tapering to 1 mm diam., upper part densely pubescent. Stamens mounted spirally on lower 60% of torus but generally fallen in herbarium specimens; carpels at the top, divergent. Stamens 50 – 60, 1 – 3 mm long, 0.5 – 0.8 mm wide; yellow when fresh, filament 0.1 – 0.2 mm long, connective with an indumentum of hairs 0.1 mm long between thecae terminating in an extension of 0.1 – 0.2 mm. Carpels 3 – 7, 3 – 5.5 mm long, 1 – 1.5 mm in diam., densely pubescent, hairs 0.05 – 0.2 mm long, velvety, appressed, white; stigma sessile, bilobed, 1 – 1.1 mm long, 0.6 – 0.9 mm wide, glabrous, yellow drying black. Fruits nearly sessile with 1 – 3 ovoid monocarps 6 – 6.5 × 2.8 – 3.2 cm, green with white speckles. Seeds 6 in yellow pulp, 2 × 1.5 cm with an indumentum of fine white hairs ( Fig. 5 ).

RECOGNITION. Similar to Mischogyne elliotiana in its flowers and fruits. Distinct in being a medium-sized tree to 25 m tall rather than a small tree or shrub 3 – 10 m tall; in having 3 – 7 carpels rather than 7 – 12; and in having sepals united in a capsular membranous calyx rather than three free reduplicate-valvate sepals; in the carpel indumentum velvety appressed with hairs 0.05 – 2 mm long, rather than with longer bristly semi-erect hairs 0.8 – 1 mm long.

DISTRIBUTION. Cameroon, Bioko ( Equatorial Guinea), Gabon ( Map 1 ).

SPECIMENS EXAMINED. CAMEROON. South Region: Nkoolong, Environs de Nko'olong , 30 km E Campo, B. Satabié 978 ( YA not seen) . Southwest Region: Njonji, Fako, along path to the lake., 200 m, [4°6' 8°59'], fr, 26 Sept. 2001, D. Kenfack 1545 ( MO *); Bakingili , Mount Cameroon National Park , Bakingili trail, above Bakingili village , 449 m, fl, 2 April 2016, T. L. P. Couoreur 1033 (photos only) . EQUATORIAL GUINEA. Bioko: Moaba - Moka Trail / Pt 141 - Pt 139, 300 m, [3°16' 8°38'6"], fl, 15 March 2007, W. R. Q. Luke 11941 (K!) . GABON. Nyanga Province: Mayumba, région du Nyanga., 24 m, [3°25' 10°40'], fl, 26 Aug. 1914, G. M. P. C. Le Testu 1768 ( BM *, BR *, L*, LISC *, P*) .

HABITAT. Lowland evergreen rain forest.

CONSERVATION STATUS. This taxon is only known from four locations: (1) The Mt Cameroon sites are at the edge of the Mt Cameroon National Park but not within it and subject to community logging. (2) The specimen from the south of Cameroon is not in the Campo-Ma’ an National Park, but in an area designat- ed as a production forest. (3) Specimens from Bioko are from within the Reserva Científica de la Caldera de Luba. The forest in the reserve is described as pristine, but a new road is already increasing development pressure in the area ( Cronin et al. 2015). (4) The exact location of the Gabonese specimen from Mayumba is unknown and it is not clear that it still exists. A “sustainable” development, including forestry, is planned for the Mayumba area (http:// www.sfmafrica.co.za/projects/gabon). There are threats to plants in three of the four known locations. From the known specimens we compute an AOO of 24 km 2 and an EOO of 66192 km 2. This justifies an IUCN category of Endangered B2ab(ii).

PHENOLOGY. Flowering in January, November. Fruiting November.

ETYMOLOGY. Meaning ̒from Gabon ̓.

VERNACULAR NAME. None recorded.

USES. None recorded.

NOTES. Annick Le Thomas (1969) described this taxon as a variety in the Flore du Gabon based on Pellegrin’ s nomum nudum Uoariastrum elliotianum (Engl. & Diels) Sprague & Hutch. var. gabonensis . Her diagnosis distinguishes the variety by fewer carpels (4 – 5) with an attenuate apex and sepals and pedicels puberulent. Her full description appears to be based on Mischogyne elliotiana , and the distinctive capsular calyx is not described.

The specimens from Mt Cameroon occur in one of the wettest environments in Africa with over 4000 mm ppa. Couvreur records the tree as up to 25 m tall, 25 cm diam. (T. L. P. Couoreur 1033), which makes it quite distinct from the smaller and more branched Mischogyne elliotiana . The leaves also have a longer and often linear acumen. This evidence justifies raising this taxon to the species level.

David Kenfack photographed fruits of this species (D. Kenfack 1545) showing hairy seeds ( Fig. 6D ). Hairy seeds are known from only a few genera ( Setten et al. 1992) and this bears further investigation.

Figures

Map 1. Distribution of all species of Mischogyne.

Fig. 2. Flower buds of Mischogyne species. A M. elliotiana var. elliotiana with old flower showing carpels below (Dalziel 761 [K000874259]); B M. michelioides showing large terminal bud (Gossweiler 9379 [K000196792]); C M. congensis (Evrard 5376 [BR0000015312655]); D M. gabonensis buds showing capsule and rupturing at anthesis (Le Testu 1768 [WAG0247284]).

Fig. 5. Mischogyne gabonensis. A flowers (Luke 11941b); B post-anthesis flower (Couvreur 1033); C fruit longitudinally sectioned along long axis (ĸenfack 1545); D seeds showing white hairs (ĸenfack 1545). PHOTOS: A QUENTIN LUKE, B THOMAS COUVREUR, C, D DAVID KENFACK.

Fig. 6. Mischogyne iddii. A habit, flowering branch; B opening flower bud; C vein network detail; D open flower; E inner face of sepal; F inner face of outer petal; G inner face of inner petal; H detail of hairs on outer face of petal; J detail of hairs on inner face of petal; K carpels on androgynophore with two stamens in situ; L carpel; M stigmatic region of L viewed from left side; N outer face of stamen; P inner face of stamen. From Marshall 1567 (K) and photos. DRAWN BY ANDREW BROWN.