Uvariopsis citrata Couvreur & Niangadouma, 2016

Couvreur, Thomas L. P. & Niangadouma, Raoul, 2016, New species of Uvariopsis (Annonaceae) and Laccosperma (Arecaceae / Palmae) from Monts de Cristal, Gabon, PhytoKeys 68, pp. 1-8 : 3-4

Uvariopsis citrata Couvreur & Niangadouma sp. nov. Figure 2

Type.

GABON, Estuaire, Monts de Cristal, near first bridge after Kinguele village , 0°46'66"N, 10°27'81"E, 14 Jun 2016, T.L.P. Couvreur 1143 (holotype: WAG!; isotypes: LBV!, P!) .

Diagnosis.

Resembles Uvariopsis sessiliflora (Mildbraed & Diels) Robyns & Ghesquière by the (sub) sessile flowers. Differs from Uvariopsis sessiliflora by the strong lemon scent of its crushed leaves or young branches (vs no lemon scent), larger leaves (40 cm vs 10-18 cm), cordate leaf base (vs acute leaf base) and ovoid-conic flowers (vs globose).

Description.

Tree 4-7 m tall, 3-5 cm in diameter at breast height (d.b.h.), slash light cream with a black ring, old branches grey, glabrous, young branches light green, pubescent. Leaves distichous, simple, entire, pinnately veined. Petiole 4-5 mm long, 4 mm in diameter, pubescent with short appressed hairs when young, grooved on top, leaf lamina inserted on top. Lamina 45-50 cm long, ca. 12 cm wide, length:width ratio 3.5-4.1, narrowly elliptic to elliptic to narrowly ovate, apex long acuminate, acumen 2-3 cm long, base cordate, coriaceous, glabrous above, glabrous below, strong scent of lemon in crushed leaves; mid rib sunken above, glabrous above, sparsely pubescent below, secondary veins 17-19 pairs, arching 4-5 mm from the margins, tertiary venation network like, raised above and under. Inflorescences cauliflorous (no ramiflorous flowers seen), sparsely spaced along the trunk, more towards the lower half of the trunk, with one to three flowers. Flowers actinomorphic, monoecious, with 6 tepals in total, differentiated in one whorl of 2 sepals and 1 whorl of 4 petals. Male and female flowers similar in size, ovoid-conic, preanthetic flowers seen only. Flowering pedicels male or female 1-2 mm when present, densely covered with short appressed hairs, light brown, up to three bracts tightly packed, covered with short appressed hairs. Sepals male or female 1.3-1.5 cm long, 4 mm wide, length:width ratio 3.5, narrowly ovate, fused for 1/5 to 1/3 of their length, valvate, apex acute, outside densely pubescent with hairs appressed, brown, inside densely pubescent with curly hairs, glabrous towards base. Petals male or female 1.3-1.5 cm long, 7-8 mm wide, 2 mm thick, length:width ratio 3.5, narrowly ovate, apex acute, base truncate, outside densely pubescent with appressed hairs, inside glabrous. In staminate flowers, receptacle conical, 7 mm long, 5 mm wide, stamens numerous, immature, 0.5 mm long, connective truncate, pale yellow. In carpellate flowers, carpels ca. 60, 4-5 mm long, ca. 0.5 mm wide, densely pubescent with long appressed hairs, ovules not observed (preanthetic), stigma cylindrical coiled, glabrous. Fruits unknown.

Preliminary conservation status.

Data deficient. DD. Uvariopsis citrata is only known by two collections and three individuals collected in the same area. The type locality is located in a mature forest within the National Park Monts de Cristal, Mbé sector, close to the road that links Kinguélé and Tchimbélé villages. However, the locality does not seem under threat to date and no changes in habitat have been seen in the last few years. However, because it is close to the road and Kinguélé the future of these populations are not certain.

Distribution.

Only known to date from Gabon, from one locality in the Monts de Cristal National Park, Mbé sector. 200-300 m in altitude.

Habitat.

This species grows in mature or old secondary forests near rivers in periodically inundated soils, or on slopes near rivers.

Etymology.

Named after the strong lemon scent of the crushed leaves and young branches one of the diagnostic characters for this species.

Paratypes.

GABON, Estuaire: Monts de Cristal National Park, Mbé Sector, near first bridge after Kinguélé village, 0°46'66"N, 10°27'81"E, 14 Jun 2016, T.L.P. Couvreur 1126 (WAG!, LBV!, P!)

Discussion.

Uvariopsis citrata is unique in the genus by the strong lemon smell of its leaves, young branches and young flowers when crushed. This character is rare in African Annonaceae only reported in one other species, also endemic to Gabon, Uvariodendron molundense (Diels) R.E.Fries var. citrata Le Thomas (Le Thomas 1969). This latter species grows in the region of Belinga. To date it remains unclear why some species have this character. Other plants around the type locality did not present this same scent. In addition, Uvariopsis citrata has sessile flowers, a character it shares with Uvariopsis sessiliflora ( Kenfack et al. 2003) endemic to Cameroon. All other Uvariopsis species have pedicilate flowers. However, Uvariopsis sessiliflora has smaller leaves (10-15 cm) and globose flower buds, while Uvariopsis citrata has leaves to 50 cm and ovoid-conic ones. The total number of species in Uvariopsis is now 19.

Figures

Figure 2. Uvariopsis citrata. A Trunk with slash (Couvreur 1126) B Entire leaf C Leaf base upper side D Leaf apex, upper side E Pre anthetic flower buds on trunk, 1: female flower, 2: male flower F Leaf base, lower side. (Couvreur 1143). Photos Thomas L. P. Couvreur.