Monanthotaxis couvreurii P.H.Hoekstra, 2016

Hoekstra, Paul H., Wieringa, Jan J. & Chatrou, Lars W., 2016, A nonet of novel species of Monanthotaxis (Annonaceae) from around Africa, PhytoKeys 69, pp. 71-103 : 78-80

Monanthotaxis couvreurii P.H.Hoekstra sp. nov. Figs 4 , 5 , Table 1

Type.

CAMEROON, Central Province , Ottotomo Forest Reserve, 45 km SW of Yaoundé, ca 5 km on main path into reserve. 3°35.21'N; 11°17.63'E, 24 April 2015, T.L.P. Couvreur 762 (holotype: WAG [3 sheets, barcodes: WAG.1576998!, WAG.1576999!, WAG.1577000!]) .

Diagnosis.

Differs from all Monanthotaxis species by the stamens that are basally connate. The leaves are similar to Monanthotaxis atopostema P.H.Hoekstra from Congo and Monanthotaxis aquila P.H.Hoekstra from Ivory Coast, but the flowers of Monanthotaxis couvreurii differ in having no staminodes and the leaves have more secondary veins with smaller spaces in between.

Description.

Liana; young branches reddish brown with dense ascending reddish brown hairs 0.1-0.2 mm, old branches greyish brown, slightly grooved,. Leaves: petioles 3-5 × 0.8-0.9 mm, slightly grooved, indumentum as branches; lamina 4.5-12.0 × 1.8-4.3 cm, length:width ratio 2.1-2.9, oblong to obovate, base cuneate to rounded, apex acute to acuminate, acumen to 1 cm, chartaceous, discolorous, adaxially glossy green, abaxially light greyish green, adaxially sparsely covered with whitish appressed hairs 0.1 mm, soon glabrescent, abaxially with scattered appressed whitish yellowish hairs 0.1-0.2 mm,, venation eucamptodromous, secondary veins 7-11, from base curving upwards, tertiary venation scalariform sometimes obscure. Inflorescences cauliflorous, ramiflorous or axillary, composed from a two-flowered rhipidium in the axils of the leaves to many-flowered clusters on the trunk; sympodial rachis 1-15 mm; flowering pedicels 4-20 × 0.2-0.6 mm, with scattered ascending to erect hairs 0.1 mm; lower bracts strongly reduced or wanting; upper bracts wanting; flower buds ovate. Flowers bisexual; sepals 3, 0.8-0.9 × 0.9-1.0 mm, triangular, apex acute, with dense yellowish hairs; receptacle flat, 1.2-2.0 mm in diameter; petals light yellow to white, in two whorls of 3, but base of inner petals visible in bud; outer petals, 3.5-5.0 × 2.0-3.5 mm, elliptic-ovate, outside with dense short yellowish hairs, inside with a few hairs near the margins; inner petals 3.0-4.5 × 1.2-1.5 mm, elliptic to narrowly ovate, outside with yellowish hairs at the apex and at the centre, inside glabrous or with a few hairs at the margins; stamens 13-15 in one whorl, connate at base, linear-obconic 0.8-0.9 mm, filaments 0.4 mm, anther cells lateral to extrorse, connective papillose, truncate, rounded from above, staminodes 0; carpels 9-12, 1.2-1.3 × 0.3-0.4 mm, subcylindric to ellipsoid, dense hairy, with 4 lateral ovules, stigma subsessile 0.2 mm, globose, glabrous. Fruits: Not seen, but according to collection Farron 7359 with 4 articles.

Distribution.

Cameroon, Central Province, Ottotomo Forest Reserve. Figure 5 .

Ecology.

Old secondary forest, on slope, at 700 m altitude.

Phenology.

Flowers collected in April and May.

Conservation status.

Proposed IUCN Red List Category: Critically Endangered (CR): B2ab(iii), only known from the Ottotomo Forest Reserve in Cameroon. The increase of human population around the reserve intensifies the pressure on the forest, while the surrounding forests are increasingly degrading ( Sassen and Jum 2007), warranting the critically endangered status of this species.

Etymology.

Named after Thomas L.P. Couvreur, a passionate Annonaceae systematist and collector of the type of this species and of Monanthotaxis latistamina P.H.Hoekstra also described in this article.

Additional specimens examined (all paratypes).

CAMEROON. Central Province: Ottotomo reserve, 5 May 1970, C. Farron 7266 (P [P01954685]); Ottotomo reserve, 26 May 1970, C. Farron 7359 (P [P01954686], YA [YA0044284]).

Discussion.

This species belongs to a group of species with predominantly ramiflorous inflorescences, bisexual flowers and ovate flower buds and looks vegetatively very similar to Monanthotaxis aquila and Monanthotaxis atopostema . For the differences between these species see Table 1 . Monanthotaxis couvreurii can be distinguished from all Monanthotaxis species in having the stamens basally connate (see figure 4F). Monanthotaxis klainei (Engl.) Verdc. also has the stamens connate in one whorl, but in that species the stamens are alternating with staminodes.

Figures

Figure 4. Monanthotaxis couvreurii P. H. Hoekstra. A-F photographs in the field of the type collection (TLP Couvreur 762). Photos: Thomas Couvreur.

Figure 5. Distribution map of Monanthotaxis couvreurii (red diamonds), Monanthotaxis latistamina (blue squares), Monanthotaxis tripetala (green triangles) and Monanthotaxis zenkeri (black asterisk).