Monanthotaxis latistamina 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 : 85-89

Monanthotaxis latistamina P.H.Hoekstra sp. nov. Figs 5 , 9 , 10 , Table 3

Type.

GABON. Ogooué-Ivindo, Ivindo National Park, along main trail departing from behind the herbarium at the Research station of Ipassa , 0°30.23'N, 12°47.59'E, 11 November 2013, T.L.P. Couvreur 565 (holotype: WAG [3 sheets, barcodes: WAG.1577028!, WAG.1577029!, WAG.1577030!]; isotype: LBV, YA) .

Diagnosis.

Closely related to Gilbertiella congolana Boutique by the papillose petals and stamens. Differs from Gilbertiella congolana by having 6 oblong stamen (vs 12 linear stamen) which are wider than deep (vs rounded in cross-section).

Description.

Scandent shrub or liana to 4 m high; young branches sparsely pubescent with appressed yellowish hairs 0.1-0.2 mm, old branches dark, blackish, soon glabrescent sometimes with a few lenticels. Leaves: Petioles 5-12 × 1.3-1.7 mm, grooved adaxially, indumentum as branches; lamina 6-13 × 3.5-7.2 cm, length:width ratio 1.6-2.7, oblong or elliptic to slightly obovate, base cuneate, rounded to subcordate with thickened black margin at base, apex acute to acuminate, acumen to 1.3 cm long, chartaceous to subcoriaceous, adaxially green, abaxially light greyish green, young leaves with a few short appressed hairs, soon glabrescent, venation eucamptodromous, secondary veins 7-8(-10) oblique, from base curving upwards, tertiary venation reticulate, raised adaxially, leaves are punctate, although difficult to see in older leaves. Inflorescences axillary or terminal, solitary, in fascicle-like rhipidia or in a to 4 cm long short lax panicle-like rhipidium with up to 6 flowers; sympodial rachis appressed pubescent to glabrescent; flowering pedicels 8-17 × 0.3-0.4mm, indumentum as sympodial rachis; lower bracts strongly reduced or wanting; upper bracts lanceolate to ovate 0.6-0.7 × 0.4-0.6 mm, same pubescence as sympodial rachis, placed halfway the pedicel; flower buds globose to slightly ellipsoid. Flowers bisexual; receptacle 1.2-1.5 mm in diameter; sepals 3, united at base, 0.8-1.0 × 1.2-1.5 mm, ovate to broadly ovate, adaxially with short appressed yellowish hairs, apex obtuse to slightly acute; petals 6 in one whorl, but 3 petals overlapping others at apex in bud, in young flowers green, 1.6-2.5 × 0.7-1.2 mm elliptic to slightly ovate, with inwardly reflexed appendage at apex, outside papillose to slightly short appressed pubescent, inside papillose, most dense at apex; stamens 6, in one whorl, alternate with petals, light green, oblong, densely papillose wider than thick 1.0-1.2 × 0.6-0.7 mm, radial width 0.2-0.3 mm, filaments 0.1 mm, anthers 2, extrorse, connective appendage small, just visible between the anthers, densely papillose, truncate; staminodes 0; carpels 6-9, 1.0-1.4 × 0.4-0.6 mm, ellipsoid densely reddish brown pubescent with 6 lateral ovules, stigma globose to slightly elongated, grooved to almost bifurcate, 0.1-0.2 mm, glabrous. Fruits reported as yellowish, not seen.

Distribution.

Gabon, province Ogooué-Ivindo. Republic of Congo, province Niari. Figure 5 .

Ecology.

Evergreen forest and forest on shallow soil at summit of hill, elev. 519-1017 m.

Phenology.

Flowers collected in May, October and November.

Conservation status.

Proposed IUCN Red List Category: Endangered (ED): B2ab(iii), EOO 17682 km2, AOO 16 km2. Although the species has quite a wide distribution, it is only known from four collections, one of which is from a protected area. The other collections are from areas under threat of logging and habitat destruction, which is why we suggest the status of endangered.

Etymology.

Named latistamina for the wide, but flattened stamens, which differentiates it from the similar Gilbertiella congolana Boutique.

Additional specimens examined.

REPUBLIC OF CONGO. Niari: Edge of the Missanda plain, 28 October 1975, P. Sita 3966 (P [P01982495],P [P01982496], WAG [WAG.1575264]; excluded as paratype) . GABON. Ogooué-Ivindo: Ca 4 km NNW of Ikei-Bokaboka, 0°57.18'N, 13°41.45'E, 18 May 2003, L. Ngok Banak 1811 (paratypes: BRLU, LBV [LBV0001649], MO [6357151], P, WAG [WAG0148822]; Belinga mountain , 1°04.87'N; 13°12.18'E, 11 November 2015, J.J. Wieringa 8320 (paratypes: WAG [3 sheets, WAG.1575172, WAG.1575173, WAG.1575174]).) .

Discussion.

This species is similar to Gilbertiella congolana Boutique from Congo (Kinshasa), but it differs in stamen number and form, furthermore Monanthotaxis latistamina has thicker petioles, while the petioles of Gilbertiella congolana are more slender (Table 3 ).

Although Monanthotaxis latistamina is similar to Gilbertiella congolana we do describe it in Monanthotaxis as Gilbertiella Boutique will be synonymized with Monanthotaxis . Boutique (1951) described Gilbertiella based on linear stamens, outer petals that cover the inner petals in bud only at the apex, and an apical appendage on the inside of the petals. These characters on their own occur in other species of Monanthotaxis as well. The outer petals overlapping the inner petals only at the apex occurs in a quarter of all Monanthotaxis species, the linear stamens occur in some species such as Monanthotaxis filamentosa (Diels) Verdc. and Monanthotaxis maputensis P.H.Hoekstra (figure 11) and a more or less developed appendage on the petals occurs in species such as Monanthotaxis le-testui Pellegrin and male flowers of Monanthotaxis cauliflora (Chipp) Verdc. and often in young flower buds. All other characteristics of Gilbertiella congolana are typical or at least normal for Monanthotaxis , such as having only a few stamens in one whorl and uniseriate stipitate monocarps. Also Walker (1971) reported a strong affinity between Monanthotaxis and Gilbertiella based on the microbaculate pollen exine. Based on all these similarities we place Monanthotaxis latistamina in the genus Monanthotaxis . Furthermore, DNA sequences confirm the placement of Monanthotaxis latistamina within the genus Monanthotaxis ( Guo et al. in press).

The specimen of Monanthotaxis latistamina from the Republic of Congo has some differences with the three specimens from Gabon. The flower buds and stems of the specimen dried very blackish and the leaves are coriaceous and greyish vs chartaceous and green in the Gabonese specimens. However the distinguishing characteristics with Gilbertiella congolana are the same as with the Gabonese specimens. More collections are needed to verify if this is just an aberrant collection or a different (sub)species. For now this collection is retained as belonging to Monanthotaxis latistamina based on the similarities in flowers and stamen, but it is excluded as a paratype.

Figures

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

Figure 9. Monanthotaxis latistamina P. H. Hoekstra. A-H drawn from the type (Couvreur 565). A Habitus B Flower bud C Open flower with 2 petals and one stamen removed D Outer petal outside E Outer petal inside F Stamen inside G Stamen lateral H Carpel. Illustration by E. Winkel.

Figure 10. Monanthotaxis latistamina P. H. Hoekstra. A-D Photographs in the field from the type collection (TLP Couvreur 565). Photos: Thomas Couvreur.