Palisota fadenii Burg & E. Bidault, 2019

Bidault, Ehoarn & Burg, Willem Joost van der, 2019, Novitates Gabonenses 90: Palisota (Commelinaceae) revisited: description of eight new species from Central Africa and notes on the identity of P. satabiei and P. bogneri, Candollea 74 (2), pp. 169-202 : 187-189

4. Palisota fadenii Burg & E. Bidault , spec. nova ( Fig. 7E–F , 8 ).

Holotypus: GABON. Prov. Haut-Ogooué: région de Moanda , forêts et galerie aux env. de Mounana , [01°25'S 13°13'E], c. 400 m, 3.I.1962, fl. & y. fr., Sita 535 ( P [ P06836329 ]!; isotype: BRLU!, G [ G00341284 ]!, MO [ MO- 3029909 ]!, P [ P06836328 , P06836338 ]!, WAG!).

Palisota fadenii Burg & E. Bidault most closely resembles P. brachythyrsa Mildbr. , P. thollonii Hua and P. preussiana K. Schum. ex C.B. Clarke , but differs from them by its smaller stature, densely hairy inflorescences forming a globose, compact thyrse, and by the long, stiff, ginger-colored trichomes on its leaf sheaths and stems.

Erect or decumbent herb to 30– 50 cm tall, not rooting at nodes, rarely branched. Stems with erect, rusty to gingercolored trichomes ± 1–2 cm long, more dense on the nodes and sheaths, internodes (8 –) 10 – 20 cm long, 2 – 4 mm in diam., brownish in sicco. Leaves 1 – 2 on nodes, reduced, and (2–)3–4(– 6) in a terminal pseudowhorl, larger; sheath 8 – 18 mm long, generally open to the swollen base; pseudopetiole 2–5 cm long; sheaths and pseudopetiole densely covered by erect, rusty to ginger-colored trichomes 1.5–3 cm long; lamina largely elliptic, 10–13.5 × 4–6.5 cm, base cuneate, margins entire with small appressed ginger-colored trichomes, apex acuminate, adaxial surface white puberulous to pubescent with erect, brown, stiff trichomes, abaxial surface densely brownish pubescent, especially on the primary venation. Inflorescences strictly terminal, 1 per apical verticil, erect, 4–8 cm long, simple; peduncle 1.5–3(4.5) cm long, with 1 persistent peduncular bract, sheathing, acuminate, densely covered by rusty to ginger-colored trichomes; the flowering portion in a subglobose thyrse 3–4.5(–6) cm in diam., with a few more bracts, each subtending a cincinnus, persistent, narrowly triangular, 6–10 mm long; cincinni spreading at anthesis then erect in fruit, with dense, fuzzy, rusty to brown pubescence, with ± 6 flowers, anthesis sequential, several cincinni often bearing an open flower at the same time. Flowers male and bisexual, pinkish when in bud, brownish at anthesis, 5–7 mm in diam., pedicel 2– 5 mm long, erect at anthesis, densely pubescent. Sepals subequal, the 2 lower ones oblong-elliptic, 2 × 0.75 mm, the upper one ovate, 2 × 2 mm, with brownochre trichomes covering the abaxial surface. Petals equal, elliptic, rounded at the apex, 2 × 1 mm, glabrous. Staminodes 3, 1 mm long, filaments with long, yellow, spreading trichomes, antherodes lacking. Stamens 3, unequal, erect, the two upper ones with a filament 1.5 mm long, glabrous, anthers flattened, ellipsoid, slightly curved, 0.9 × 0.5 mm, ± 0.1 mm thick, basifixed, yellow; the lower stamen with a filament 1 mm long, glabrous, anther obovate-oblong, 0.9–1 × 0.7–1 mm,± 0.3 mm thick, curved at the apex. Ovary obovoid, 0.5–0.75 mm long, densely pubescent, the trichomes 1 mm long, style 2.5–3 mm long, glabrous, pale lilac, stigma clavate. Fruits ovoid berries, apex acuminate, ± 5 mm in diam. in sicco, densely pubescent, red when mature, bearing ± 4 seeds. Mature seeds not seen.

Etymology. – This species is named in honor of Dr. Robert B. Faden of the Smithsonian Institution ( US), who in 2011 identified the two collections known at the time as belonging to an undescribed taxon, and in recognition of the immense contribution he has made to our knowledge of Commelinaceae around the world.

Distribution and ecology. – Palisota fadenii is known from Gabon (Haut-Ogooué and Estuaire provinces) and Republic of Congo (Kouilou province) ( Fig. 9 ). Only three collections have been made over a 50 year period, and this species thus appears to be rare. It grows in the understory of secondary terra firme forest (Ikabanga et al. 173) or gallery forest ( Sita 535). It is known from 50 to 400 m elevation.

Conservation status. – The EOO is 82,827 km ², greatly exceeding the threshold for “Vulnerable” status under Criterion B1, and the AOO is estimated at 12 km ², at the lower end of the range for “Endangered” status under Criterion B2. Palisota fadenii is known from 3 collections representing 3 sub-populations: one from Kouilou province in Republic of Congo in 1974 ( Sita 3711); one from the Moanda region in Haut-Ogooué province, collected in 1962 ( Sita 535); and one from near Libreville collected in 2011 (Ikabanga et al. 173). We consider that the sub-population represented by Sita 3711 has not been extirpated because the area is still largely forested and is now included within a National Park (Conkouati-Douli NP). The sub-population in the Moanda region is located near a mine site, but not within the footprint of the current mining operations. Nevertheless, it is in the direct vicinity (200 meters) of a plateau that will be subjected to mining in the near future. As a consequence, this sub-population is believed not to have been extirpated as yet, but it is threatened by the future development of the mine. The sub-population located near Libreville (Malibé 2) is situated outside the boundaries of the Mondah Forest Reserve and hence is not protected from threats associated with urbanization that has drastically increased over the last few decades in the area and is still increasing today. The persistence of this subpopulation is doubtfull and it could be regarded as extirpated. Each of the 3 sub-populations is represented by a single collection, and together they represent 2 or 3 locations with respect to the most important threat (urbanization). Palisota fadenii is highly threatened by urbanization and mining activities, which have led to or will likely lead to the extirpation of two sub-populations, and thus an inferred and projected decline in its EOO, AOO, quality of its habitat, number of locations, and number of mature individuals. Palisota fadenii therefore qualifies as “Endangered” [EN B2ab(i,ii,iii,iv,v)] according to the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Palisota fadenii is the rarest species treated in this study and has never been photographed in the field. The description of the color of the flower is based on the notes accompanying Sita 3711, and only few open flowers were present on the herbarium specimens observed. The disjunction in the distribution of this species (350 and 500 km separate the known subpopulations) and the fact that it has been found in coastal as well as continental areas is striking, especially since many Palisota collections have been made in Gabon during the last few decades. In addition to its overall rareness, the paucity of collections of this species could also be explained by its unusual phenology, with flowering taking place in January and fruiting in March and April. Palisota fadenii is easily recognizable among the decumbent species by its subglobose thyrse bearing red fruits. Nevertheless, it resembles P. brachythyrsa in sharing these features, although the latter species belongs to the group of free-standing Palisota with a robust stem. Palisota fadenii can also be distinguished from P. brachythyrsa by its thyrse being at least as wide as long and bearing multiple elongated cincinni giving it a clearly subglobose shape, whereas P. brachythyrsa has a shortly elongated thyrse with only a few cincinni that remain short, even in late fruiting stages, giving it an irregular shape.

Paratypus. – GABON. Prov. Estuaire: Libreville , Canton Tsini-Otandé , villages Malibé 2 , 00°36'30"N 09°24'08"E, 50 m, 17.III.2011, fr., Ikabanga et al. 173 ( LBV, MO). REPUBLIC OF CONGO. Prov. Kouilou: P.C.A. de N’Zambi , rte N’Gongo , à 5 km de N’Tiétié, [03°54'S 11°15'E], c. 50 m, 30.IV.1974, fr., Sita 3711 ( P).

Figures

Fig. 7. – Palisota cristalensis E. Bidault & Burg (A–D) and P. fadenii Burg & E. Bidault (E–F). A. Living plant in habitat; B. Inflorescence showing closed flowers; C. Detail of an open flower; D. Detail of pubescence on the upper side of the lamina; E. Detail of an open bisexual flower showing the reflexed lower stamen still in place, and the two upper stamens removed; F. Detail of an open bisexual flower from the outside, showing the reflexed lower stamen still in place, one of the upper stamens, and the calyx with one larger sepal.

Fig. 8. – Palisota fadenii Burg & E. Bidault. A. Habit; B. Inflorescence; C. Bisexual flower; D. Upper sepal; E. One lower sepal; F. Petal; G. One upper stamen; H. Lower stamen; I. Staminode; J. Ovary and pistil. [Sita 535] [Drawings: D. Geffard-Kuriyama & L. Longou]

Fig. 9. – Distribution of Palisota bogneri Brenan (stars), P. plicata E. Bidault & Burg (squares), and P. fadenii Burg & E. Bidault (triangles). Elevation is represented in levels of grey, and protected areas as shaded.