Monanthotaxis atewensis 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 : 74-77

Monanthotaxis atewensis P.H.Hoekstra sp. nov. Figs 2 , 3

Type.

GHANA. Eastern Region, Atewa Range Forest Reserve , 2 June 1973, J.B. Hall GC43672 (holotype: WAG [2 sheets, barcode WAG0019665!, WAG0019666!]; isotypes: GC!, K [K000040198!], MO [2189255]!)

Monanthotaxis atewae Hawthorne & Jongkind (2006: 72); invalid: description in English, no type designated (this termination, although admissible, does not follow recommandation 60D of the ICBN).

Diagnosis.

Easily distinguishable from all other Monanthotaxis species by the lanceolate sepals 1 cm long. Resembles Monanthotaxis stenosepala (Engl. & Diels) Verdc., but differs in the longer sepals, erect hairs on the leaves and branches, and a larger number of seeds per monocarp.

Description.

Scandent shrub or liana, to 9 m tall; young branches dark brown, with scattered erect reddish brown hairs 0.3-0.5 mm, old branches light brown, glabrescent with a few lenticels. Leaves: petioles 3-5 × 1.0-1.2 mm, grooved adaxially, indumentum as branches; lamina 5.7-15.9 × 2.4-5.4 cm, length:width ratio 2.0-3.1, oblong to slightly oblanceolate or obovate, base rounded, truncate or subcordate, apex acute to acuminate, acumen to 1.5 cm, chartaceous, abaxially greyish, adaxially glabrous, the midrib impressed with a few short hairs near the base, abaxially sparsely to densely covered with short erect reddish brown hairs, venation eucamptodromous, secondary veins 8-14, first straight halfway curving upwards, tertiary venation scalariform. Inflorescences leaf-opposed, composed of a solitary flower to a 3-flowered rhipidium; sympodial rachis 2-4 mm; flowering pedicels 21 × 0.7 mm, with short yellowish ascending to erect hairs; lower bract strongly reduced or wanting; upper bract around the middle of the pedicel, ovate, 1.7 × 1.4 mm, densely covered with short appressed hairs; sepals 3, free, 10-12 × 2.6-2.7 mm, lanceolate, apex acute, with dense short appressed hairs; receptacle 3.0 mm in diameter, flat; petals unknown; stamens unknown, scars in a single whorl; carpels 1.2 × 0.5 mm, ellipsoid, dense hairy, stigma elongate 0.5 mm, grooved, glabrous. Fruits: pedicels 20-37 × 0.6-1.1 mm; sepals persistent or caducous; stipes 4-6 mm long, slightly grooved; monocarps 1-9, ellipsoid with 1 to 5 seeds, 13-35 × 5-6 mm, slightly to strongly constricted between the seeds, slightly verrucose, apex apiculate, apex to 2.0 mm, with scattered short erect hairs, unripe fruits green. Seeds 9 × 6 mm, ellipsoid, base and apex rounded, tawny brown, raphe visible from base to apex, ruminations lamelliform.

Distribution.

Ghana, Eastern Region, Atewa Range Forest Reserve. Figure 2 .

Ecology.

Forest, in thicket, at 750 m altitude.

Phenology.

Fruiting in May and June.

Conservation status.

Proposed IUCN Red List Category: Critically Endangered (CR): B2ab(iii), only known from the Atewa Range Forest Reserve and although it is a protected area, the forest is under threat of bauxite mining and logging ( Kusimi 2015; Ntiamoa-Baidu et al. 2000). Furthermore, the species has not been collected in more than 40 years.

Etymology.

Named after the Atewa Range Forest Reserve in Ghana, to which this species seems to be endemic.

Additional specimens examined (paratypes).

GHANA. Eastern Region: Atewa Range Forest Reserve , 12 May 1967, J.B. Hall GC36426 (K [K000040199], WAG [WAG0019664]) .

Discussion.

This species can easily be distinguished from all other species of Monanthotaxis by the large lanceolate sepals. The species is similar to Monanthotaxis stenosepala (Engl. & Diels) Verdc., which also has lanceolate sepals and light brown older branches. However, the sepals of Monanthotaxis stenosepala are 4 to 6 mm vs 10 to 12 mm in Monanthotaxis atewensis and the pubescence and number of seeds is different as described in the diagnosis. Two fruiting specimens from Liberia (Stoop 331 and Adam 26189) closely resemble Monanthotaxis atewensis , but no sepals are present to verify the identification. Furthermore, the monocarps are more densely verrucose and the peduncle is shorter and the pedicel larger than the two specimens of Monanthotaxis atewensis from Ghana. More material or more recent material for DNA extraction is needed to assess the status of those specimens from Liberia.

For now we consider this species an endemic to the Atewa Range. This is the first plant species that is endemic to this mountain range. However, for several Upper Guinean endemics (e.g. Dorstenia embergeri Mangenot) this range is their most eastern outpost. Some other plants are only known from these mountains and one or two other localities in Ghana. The Atewa Range is home of 3 endemic butterfly species ( McCullough et al. 2007). This new endemic urges for a strict protection of this unique mountain chain.

Figures

Figure 2. Distribution map of Monanthotaxis aquila (blue triangle) and Monanthotaxis atewensis (red square).

Figure 3. Monanthotaxis atewensis P. H. Hoekstra. A, B, D drawn from the type (Hall & Lock GC 43672) C drawn from Hall & Enti GC 36426. A Leaf B Leaf detail C Old flower D Fruit. Illustration by M. Spitteler, from Hawthorne and Jongkind (2006).