Sirdavidia solannona Couvreur & Sauquet, 2015

Couvreur, Thomas L. P., Niangadouma, Raoul, Sonke, Bonaventure & Sauquet, Herve, 2015, Sirdavidia, an extraordinary new genus of Annonaceae from Gabon, PhytoKeys 46, pp. 1-19 : 5-7

Sirdavidia solannona Couvreur & Sauquet sp. nov.

Type.

Gabon, Estuaire, Monts de Cristal, near first bridge after Kinguele, 0°46'66"N, 10°27'81"E, T.L.P. Couvreur 596, 15 Nov 2013, Fl. & Fr., holotype: WAG!; isotypes: LBV!, P!, YA!.

Tree 4-6 m tall, 2 to 4 cm in diameter at breast hight (d.b.h.), bark dark brown with patches of green, old branches black, glabrous, young branches black, sometimes pubescent. Leaves distichous, simple, entire, pinnately veined. Petiole 3-4 mm long, 2 -3 mm in diameter, glabrous or sparsely pubescent when young, slightly grooved on top, leaf lamina inserted on top. Lamina 20-26 cm long, 4.5 to 9 cm wide, length:width ratio 2.5 to 4.5, narrowly elliptic to elliptic to narrowly ovate to ovate, apex long acuminate, acumen 2-3 cm long, base obtuse, coriaceous, young sparsely pubescent to glabrous above, glabrous below, old leaves glabrous above and below, mid rib sunken above, sparsely pubescent when young below, glabrous above, glabrous above and below when old, secondary veins 9-12 pairs. Inflorescences axillary, on old branches and cauliflorous towards the base of the trunk. Sympodial rachis up to 6 mm long, but sometimes up to 1.5 cm long, densely covered with short appressed hairs, with 0-10 minute densely packed lower bracts densely pubescent brown. Flowering pedicels 2 to 10 mm long, densely covered with short appressed hairs, red, upper bract inserted at base or up to ½ of pedicel, covered with short appressed hairs, red. Flowers actinomorphic, bisexual or unisexual staminate (androdioecious), with 9 tepals in total, differentiated in one whorl of 3 sepals and 2 whorls of 3 petals, all alternate. Sepals 2-3 mm long, 1.5-2 mm wide, length:width ratio 1.5, ovate, valvate, apex acute, base truncate, densely covered with short appressed hairs outside, glabrous inside, red. Outer petals 4-10 mm long, 2.5 to 5 mm wide, length:width ratio 2 to 2.5, elliptic, apex acute, base truncate, densely pubescent with appressed hairs outside, densely pubescent with short tomentose hairs inside, deep red. Inner petals 4-9 mm long, 2-4 mm wide, length:width ratio=2 to 2.5, elliptic, apex acute, base truncate, densely pubescent with short tomentose hairs outside, densely pubescent with short tomentose hairs inside along margins, glabrous towards center, deep red. Petals spreading horizontally or recurving backwards at anthesis. In staminate and bisexual flowers, stamens 16-19, 3-4 mm long, outer ones shorter than inner ones, filament shorter than 0.2 mm, narrow, connective umbonate (tongue shaped), glabrous, bright yellow. Anthers introrse, probably opening by two longitudinal slits. In bisexual flowers, carpel one, 4-5 mm long, ca. 1 mm wide, densely pubescent with silvery long appressed hairs, ovules uniseriate, 7-10, stigma cylindrical coiled, 2-3 mm long, sparsely pubescent towards the top, white cream. Mature fruits not seen, young fruiting pedicel 6 mm long, densely pubescent with appressed hairs. Young monocarp cylindrical, densely pubescent with silvery appressed hairs. Seeds not seen. (Figs 3 and 4)

Phenology.

Flowers collected in April and November, young fruits collected in November.

Distribution and habitat.

Sirdavidia is endemic to Gabon, with three known collections: two near the Kinguele dam in the Monts de Cristal National Park, Mbé sector, and one south of the Ivindo National Park (Fig. 2). Floristic comparisons in Gabon emphasize that the Monts de Cristal flora has a high resemblance with many other areas across Gabon, including the Ivindo NP region ( Wieringa and Sosef 2011). Thus it is not unusual to find species occurring in Monts de Cristal and elsewhere in the county. Sirdavidia grows in the understory of mature to old secondary rain forests around 300-600 m, near rivers or on inundated soils.

Preliminary conservation assessment.

Endangered [EN B1ac]. Two localities in Gabon are known for this species: Monts de Cristal N.P. and south of the Ivindo N.P. The population found in Kinguele (Monts de Cristal) was close to the road and several (around 10) individuals were seen. We also looked for this species in other parts of the Park (around Tchimbélé) and did not see it again. The herbarium specimen collected from Ivindo indicates "en peuplement" (in population) suggesting that several individuals were seen. However, the coordinates on the herbarium sheet place this collection outside the national park. The Area of occupancy (AOO) is 12,000 km² and the Extent of occurrence (EOO) is 6.2 km², suggesting a very restricted overall distribution. We thus suggest a status of endangered given that only a handful of individuals have been seen and that these populations are quite close to disturbances.

Etymology.

The species name epiteth highlights the striking resemblance with flowers of some species of Solanum , an unusual and new feature for a flower of Annonaceae .

Note.

The androdioecious nature of Sirdavidia solannona has yet to be properly confirmed. We only saw two individuals one of which appeared to have only staminate flowers. Because other members of the tribe Piptostigmateae are known to have this condition, it would not be surprising.

Paratypes.

Gabon: Estuaire, Monts de Cristal National Park, near first bridge after Kinguele, 0°46'64"N, 10°27'80"E, T.L.P. Couvreur 597, Fl., 15 Nov 2013, Fl. & Fr. (LBV!, P!, WAG!, YA!); Ougoué-Ivindo, Ivindo National Park, camp elephant, A. Moungazi 1544, Fl., 10 Avr 204 (BR!, LBV, WAG).