Monanthotaxis tripetala 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 : 93-95

Monanthotaxis tripetala P.H.Hoekstra sp. nov. Figs 5 , 13

Type.

CAMEROON. East Province , 15 km E of Dimako, village halfway Bertoua-Doumé, 11 June 1965, A.J.M. Leeuwenberg 5828 (holotype: WAG (2 sheets, barcodes: WAG0110801!, WAG0110802!); isotypes: B [B100190273!], BR [BR0000014126253], C, EA!, K!, LISC, MO, P [P01967268!], PRE, YA) .

Diagnosis.

Differs from other Monanthotaxis species in having bisexual flowers with three thick outer petals, and wanting or strongly reduced inner petals. The other species of Monanthotaxis with three petals or reduced inner petals have unisexual flowers, such as Monanthotaxis diclina (Sprague) Verdc. and Monanthotaxis cauliflora (Chipp) Verdc.

Description.

Liana, 3 m high, diameter 11 mm; young branches reddish brown, with very short appressed reddish brown hairs, old branches dark brown, cylindrical, glabrescent with few lenticels. Leaves: petioles 2-4 × 0.6-1.0 mm, indumentum as branches; lamina 4.2-12.3 × 1.8-4.9 cm, length:width ratio 1.8-2.8, oblong to elliptic, base rounded, with thick globose glands at base, apex acute to acuminate, subcoriaceous, discolorous, adaxially glossy dark green, abaxially dull greenish white, adaxially glabrescent, young with scattered appressed white hairs, midrib impressed, glabrescent with appressed yellowish hairs, abaxially glabrescent with scattered appressed white hairs, more dense and yellowish on midrib, venation eucamptodromous, secondary veins 7-9, from base curving upwards, tertiary venation scalariform, not visible adaxially. Inflorescences axillary, composed of a solitary flower or a 2-flowered rhipidium; sympodial rachis 0-6 mm with yellow appressed hairs; flowering pedicels 12-20 × 0.2-0.4 mm, with appressed yellowish hairs; lower bract wanting; upper bract in the upper half of the pedicel or wanting, lanceolate, 0.5 × 0.2 mm with dense hairs; flower buds rounded. Flowers bisexual; sepals 3, free, 0.5 × 0.8-1.0 mm, broadly ovate, apex obtuse, with dense yellow appressed hairs; receptacle 1.5 mm in diameter, flat; petals 3(-4) in one(-two) whorls; outer petals, 2.0-2.2 × 2.2 mm, ovate, with appressed yellowish hairs on the outside, and papillose near the apex on the inside; inner petals usually wanting, rarely a single strongly reduced petal present, 1.5 × 0.5-0.6 mm, elliptic, with scattered yellowish papillae on the outside and base of the inside; stamens 9-12 in 1 whorl, free, linear-clavate, 1.2 mm long, filaments 0.6 mm long, anther cells extrorse to lateral not hiding connective, glabrous, staminodes 0; carpels 9, 1.1-1.2 × 0.3 -0.4 mm, subcylindric to ellipsoid, densely hairy, ovules 3-4 lateral, stigma subsessile 0.1-0.2 mm, glabrous. Fruits: unknown.

Distribution.

Cameroon, East province and Gabon, Ogooué-Ivindo. Figure 5 .

Ecology.

Evergreen Forest and Old secondary Forest, at 515-650 m altitude.

Phenology.

Flowers collected in June.

Conservation status.

Proposed IUCN Red List Category: Endangered (ED): B2ab(iii), EOO 6370 km2, AOO 16 km2. This species is only known from 4 collections from 3 locations of which only one in a protected area. The other location (Belinga) is under threat of mining companies and the location in Cameroon is in an area with increasing human population growth, therefore we suggest the status of endangered.

Etymology.

Named for the three petals, one of the diagnostic characteristics of this species.

Additional specimens examined (all paratypes).

GABON. Ogooué-Ivindo: Station d’Ipassa, 22 Jun 1978, J. Florence 1409 (P [P01985718]); Belinga, A. Moungazi 252 (P [P01982463]); Ipassa reserve , 0°30.39'N; 12°47.65'E, 7 Nov 2015, J.J. Wieringa 8229 (WAG [WAG.1575731, WAG.1575732, WAG.1575733, WAG.1575734] & spirit collection [WAG0116914]) .

Discussion.

This species can easily be distinguished from all other Monanthotaxis species by the small bisexual flowers with 3 outer petals and wanting to strongly reduced inner petals. Some other species exist, such as Monanthotaxis cauliflora (Chipp) Verdc., Monanthotaxis diclina (Sprague) Verdc. and Monanthotaxis mortehanii (De Wild.) Verdc., which have reduced inner petals, but those have unisexual flowers. Another probably new species from Cameroon which is currently still under study, also has completely wanting inner petals, but also that species has unisexual flowers.

The type specimen from Cameroon has reflexed and thickened edges at the leaf base (e.g. figure 13B), which is wanting in the specimens from Gabon, where only a slight depression can be seen next to the petiole insertion. This character is variable in other species as well, such as Monanthotaxis schweinfurthii (Engl. & Diels) Verdc. The very distinctive, small flowers with only 3(-4) petals in the Gabon specimens make these specimens belong to Monanthotaxis tripetala .

The specimen of Moungazi 252 has a gall on one of the branches, which has not been observed in any of the currently collected material of the Monanthotaxis species, while the collection of Wieringa 8229 has many brown velvety galls on one of the leaves (WAG spirit collection). The latter type of gall has been observed in other Monanthotaxis species in Central Africa.

Figures

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

Figure 13. Monanthotaxis tripetala P. H. Hoekstra. A-J drawn from the type (Leeuwenberg 5828). A Habitus B Leaf base abaxially C Leaf base adaxially with inflorescence D Flower with one petal removed E Petal inside F Flower petals removed G Stamen outside H Stamen inside I Stamen lateral J Carpel. Illustration by H. de Vries.