Palisota leewhitei Burg, O. Lachenaud & 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 : 189-192

5. Palisota leewhitei Burg, O. Lachenaud & E. Bidault , spec. nova ( Fig. 10 , 11A–C ).

Holotypus: GABON. Prov. Estuaire: Forêt Classée de la Mondah , 00°34'27"N 09°20'02"E, 20 m, 3.III.2011, fr., Lachenaud et al. 1165 ( BR!; isotype: LBV!, MO!).

Palisota leewhitei Burg, O. Lachenaud & E. Bidault differs from all other Palisota species by the combination of a creeping habit, long, ginger-colored trichomes on the margins of the canaliculate pseudopetiole, and the short inflorescences barely emerging from the leaf litter, hidden under the leaves and among the roots.

Creeping and decumbent herb, stems on or partially hidden in the litter, erect portion ± 10 –15 cm tall, subpopulations forming patches completely covering the ground; stems 5 mm in diam., purple, bearing abundant roots growing through the sheath base, covered with yellow root hairs and forming a cuff surrounding the stem. Leaves alternate, spirally arranged along the shoot, a few aggregated at the apex; sheath ± 12 mm long, open for half its length, purple, barely or not swollen at base; pseudopetiole short, 1–2 cm, canaliculate, green or brown to purple, bearing long ginger-colored trichomes at the margins; lamina narrowly obovate to obovate-elliptic, 7–13 × 3.5–4.5 cm, margins entire with small appressed ginger-colored trichomes, these becoming longer and stiff towards lamina base; upper surface bright green, shiny, lower surface lighter green, dull. Inflorescences strictly axillary, hidden under the stems and leaves or in the litter among the roots, or barely emerging, ± 5 cm long, simple, peduncle short, with 1 basal bract, widely ovate, with long indument at the apex, the peduncle bearing ± 3 similar pseudowhorled bracts along with several more linear bracts, indument of equal density, with ± 5 terminal flowers borne in 1 or 2 cincinni. Flowers male and bisexual, ± 10 mm in diam., white in bud and at anthesis, pedicel 15–20 mm long, becoming spirally contorted after flowering and turning purplish, woolly pubescent and also with a few stiff trichomes, perianth reflexed after anthesis, then closing again. Sepals sub-equal, oblong, 6 × 2 mm, petaloid, the upper one slightly shorter and more robust, white to greenish white, pinkish at the apex of the abaxial surface, with a few wrinkled trichomes. Petals similar to sepals, 6 × 2(–2.5) mm, but glabrous and totally white. Staminodes 3, filaments with long, white, spreading trichomes, antherodes lacking. Stamens 3, unequal, clearly erect, filaments white, the two upper ones with a filament 1.6–1.8 mm long, glabrous, anthers oblong, curved, 1.5 × 0.6–0.7 mm, sub-basifixed, yellow; the lower stamen more robust, filament 2.5 mm long, glabrous, anthers 2 × 2 mm, pollen sacs curved, yellow, reniform, dorsifixed. Ovary bottle-shaped to ellipsoid, 1.5 × 0.8 mm, with a few stiff trichomes, style 1.5 × 0.3 mm, glabrous, white, stigma truncate. Fruits ovoid, slightly oblique berries, red, weakly triangular in cross section, 2– 2.5(– 2.7) × 1 cm, with a few stiff apical trichomes, pedicel spiraled. Seeds ellipsoid, 4 × 3 mm, covered by a thin, pale brown, transparent arilloid skin, testa beneath smooth with 20–30 very faint grooves, embryotega depressed, round, light gray, hilum wart-like, situated in a depression.

Etymology. – This species is named after Prof. Lee White, former Executive Secretary of the Agence Nationale des Parcs Nationaux (ANPN), the Gabonese National Parks Agency, and now Minister of Forest, Sea, and the Environment, in recognition of his work towards the protection of biodiversity in the Mondah forest and in Gabon in general. Prof. White was also one of the first person to collect material of Palisota leewhitei .

Distribution and ecology. – Palisota leewhitei is endemic to Gabon and is known only from the Mondah forest, a protected area a few kilometers northwest of Libreville, where it is locally abundant ( Fig. 12 ). This species has been recorded in low elevation (2 to 20 m) terra firme hyper-humid forest, where it forms dense, ground-covering patches.

Conservation status. – The EOO cannot be calculated since this species is known from a single sub-population, and the AOO is estimated at 8 km ², below the threshold for “Critically Endangered” status under Criterion B2. Palisota leewhitei is known from 6 collections, all made between 1992 and 2018 in the Mondah Forest Reserve, which represent a single sub-population. The most recent collection dates from 2018, confirming that the sub-population has not been extirpated. Although it is located within a protected area, with on-site documentation to inform the public of its narrow-endemic status, P. leewhitei is subjected to the effects of human activities and may be impacted by stochastic events within a very short time period, such as illegal land clearing or logging in the Mondah forest, that could rapidly result in a change of status to Critically Endangered or could even render it Extinct. Palisota leewhitei therefore qualifies as “Vulnerable” [VU D2] according to the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Palisota leewhitei resembles other member of the genus bearing short, erect inflorescences and exhibiting the same habit, such as P. cristalensis and P. plicata . It can, however, be distinguished from this latter by its smaller, not plicate leaves, its purple petiole with erect stiff trichomes, and its shorter inflorescences. Though we have not been able to examine the sterile collection Aké Assi 16101 cited by BRENAN (1984) as belonging to P. satabiei , we suspect it could represent P. leewhitei based on the description of the pubescence provided by Brenan (long rusty trichomes on the petiole, lamina glabrous except for an appressed pubescence on the margins) and the fact that it was collected in the Mondah forest, in which case it would be the first collection of this species. Palisota leewhitei was recognized to be a new species by the late C. Wilks, who pointed it out to Prof. White, long before we began studying Palisota . M.E. Leal, who previously worked for the Missouri Botanical Garden in Gabon, collected material of P. leewhitei , duplicates of which were sent to the Smithsonian Institution, where R. Faden confirmed that it was a taxonomic novelty, although he never formally published it. The species was subsequently collected and photographed multiple times by several botanists and naturalists who visited the Mondah forest, including by Prof. White, who encouraged several researchers working in Gabon at the time (including M. Leal, G. McPherson, T. Stévart and G. Walters) to describe it. Finally, O. Lachenaud collected material in 2011 that has been designated as the type, and drew to the attention of the authors the fact that it was a taxonomic novelty. The Mondah Palisota has been depicted in several books ( VANDE WEGHE, 2005; VANDE WEGHE et al., 2016) as an example of the many narrowly endemic species restricted to the Libreville peninsula ( WALTERS et al., 2016).

Paratypi.– GABON. Prov. Estuaire: Forêt de la Mondah , NNW of Libreville , 00°31'59"N 09°20'59"E, 20 m, 29.II.1992, fr., Breteler 10867 ( WAG); ibid. loco, 11.IV.2006, fr., Leal et al. 1032 ( MO); ibid. loco, 3.XI.2011, fl., Maas et al. 10079 ( WAG); ibid. loco, 2.XI.2014, fl., White s.n. ( BRLU); ibid. loco, 20.X.2018, fl., White s.n. ( BRLU, LBV, MO).

Figures

Fig. 10. – Palisota leewhitei Burg, O. Lachenaud & E. Bidault. A. Habit; B. Axillary root; C. Portion of stem with inflorescence, axillary roots, pseudopetiole; D. Male flower; E. Sepal, interior view; F. Upper sepal, side view; G. Petal, side view; H. Lower sepal, side view; I. Ovary and pistil; J. Lower stamen; K. One upper stamen; L. Upper staminode; M. One lower staminode; N. Staminodial hair; O. Ovary hair; P. Fruit, side and dorsal views. [A–O: Maas et al. 10079; P: Lachenaud et al. 1165] [Drawings: H. de Vries]

Fig. 11. – Palisota leewhitei Burg, O. Lachenaud & E. Bidault (A–C) and P. plicata E. Bidault & Burg (D–G). A. Living plants in habitat; B. Inflorescence showing capillary roots, open and closed flowers; C. Mature fruit; D. Living plants in habitat; E. Inflorescence with open flowers; F. Detail of an open flower; G. Mature fruit. [A, C: Lachenaud et al. 1165; D–E: Bidault et al. 3561; F–G: Bidault et al. 3576] [Photos: A, C: O. Lachenaud; B: J.-P. Vande Weghe; D–G: E. Bidault]

Fig. 12. – Distribution of Palisota satabiei Brenan (squares), P. leewhitei Burg, O. Lachenaud & Bidault (stars), and P. stevartii Burg & E. Bidault (triangles). Elevation is represented in levels of grey, and protected areas as shaded.