Palisota plicata E. Bidault & Burg, 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 : 193-195

6. Palisota plicata E. Bidault & Burg , spec. nova ( Fig. 11D–G , 13 ).

Holotypus: GABON. Prov. Estuaire: Monts de Cristal , Concession SEEF , rive E du Komo , 00°23'13"N 10°35'37"E, 548 m, 6.XI.2017, fl. & fr., Bidault et al. 3576 ( MO [ MO- 3047496 ]!; isotype: BR!, BRLU!, G [ G00341285 ]!, LBV!, P!, WAG!).

Palisota plicata E. Bidault & Burg most closely resembles P. leewhitei Burg, O. Lachenaud & E. Bidault but differs by the combination of its plicate, obovate leaves, longer inflorescences bearing flowers above the litter, swollen stems at the insertion of the sheath, and an overall more robust habit.

Creeping and decumbent herb, rhizome-like rooting stem to 30 cm long, occasionally dichotomous, with an erect apical portion ± 10–15 cm tall, in small gregarious subpopulations forming patches of individuals of various sizes. Stems fleshy, shortly brown woolly pubescent, glabrescent, internodes 0.5–3.5 cm long, 5–7 mm in diam. in sicco, light green or dark mauve in vivo, brownish in sicco, bearing axillary roots not growing through the sheath base, covered with abundant yellow root hairs, occasionally forming a cuff surrounding the sheath and stem. Leaves alternate, spirally arranged along the aerial part of the stem, in an apical pseudoverticil; sheath 7–15 mm long, open for a quarter to a third of its length, occasionally to its swollen base that forms a whitish-green or dark mauve bulge, sometimes longitudinally striped; pseudopetiole absent or to 5 cm long, if present bearing long, ginger-colored trichomes on the margins; lamina obovate to obovate-elliptic, 16–31 × (3.5–) 5.5–10 cm, base long-decurrent, plicate, margins entire, with small, appressed, ginger-colored trichomes, secondary venation prominent on both surfaces, upper surface green to dark green, whitish woolly sericeous when young, glabrescent, lower surface glaucous green to glaucous silver, persistent whitish woolly sericeous. Inflorescences strictly axillary, always borne on the aerial part of the stem, erect to rarely pendulous, 3–5 cm long, simple; peduncle 1–1.3 cm long, with (2 –)3 persistent peduncular bracts, sheathing, acuminate, margins densely covered by ginger-colored trichomes; the flowering portion with a few more bracts, each subtending a cincinnus, caducous, narrowly triangular, up to 1 cm long; cincinni with ± 6 flowers, anthesis sequential, several cincinni often bearing an open flower at the same time. Flowers bisexual, 9–10 mm in diam., pedicel 12–15 mm long, erect at anthesis, becoming spirally contorted after flowering, perianth sharply reflexed at anthesis, then closing again. Sepals equal, oblong, 5– 6 × 1.5– 2 mm, petaloid, white with brown-ochre trichomes at apex on the abaxial surface. Petals similar to sepals, 4.5 × 1.5–2 mm, glabrous. Staminodes 3, filaments with long, white, spreading trichomes, antherodes lacking. Stamens 3, unequal, erect, filaments white, the two upper ones with a filament 2.8–3 mm long, glabrous, anthers oblong, curved, 1.5 × 0.8 mm, sub-basifixed, yellow; the lower stamen more robust, filament 3–3.2 mm long, glabrous, anthers 1.5 × 1.2 mm, pollen sacs curved, reniform, sub-basifixed. Ovary bottleshaped to ellipsoid, 1.5 × 0.8 mm, with a few stiff trichomes, style 2.5 mm long, glabrous, yellowish white, stigma truncate, white. Fruits irregularly ovoid, slightly oblique berries, weakly triangular in transverse section, green becoming bright red, 11–15 × 6–7 mm in sicco, with sparse, thin, erect pubescence, apex more or less acuminate, pedicel spirally contorted, becoming dark purple. Seeds globose or polygonal with rounded and flat sides, ± 4 mm in diam., black in vivo, brown in sicco due to the thin, pale brown, transparent arilloid skin, testa beneath smooth, with 20–30 clearly marked, rounded, shallow ribs surrounding the seed, light gray, embryotega markedly depressed, whitish, hilum wart-like, situated in an evident depression.

Etymology. – The epithet of this species refers to the plicate character of the leaves.

Distribution and ecology. – Palisota plicata is known from five collections made in Parque Nacional de Monte Alén in Equatorial Guinea, three collections from in the Cristal Mountains in Estuaire province, Gabon, and one from Ngounié province in Gabon ( Fig. 9 ). It grows in the understory of mature to secondary hyper-humid forests on terra firme, on slopes, ridges or nearby rivers, but not in inundated areas. It is known from 132 to 1,200 m elevation.

Conservation status. – The EOO is 9,106 km ², within the range for “Vulnerable” status under Criterion B1, and the AOO is estimated at 28 km ², which is within the range for “Endangered” status under Criterion B2. Palisota plicata is known from 9 collections, representing 6 sub-populations, 3 of which are located in the Parque Nacional de Monte Alén. Two sub-populations were collected in the Société Equatoriale d’Exploitation Forestière (SEEF) logging concession in the Cristal Mountains, both of which are threatened by logging activities, and one is also by flooding associated with a planned hydroelectric dam on the Komo river, which is expected to lead to its extirpation. These 6 sub-populations represent 4 locations with respect to the most important threat (a hydroelectric project). Palisota plicata is threatened by forestry in Ngounié province and the Cristal Mountains, and flooding associated with the development of a hydroelectric project, also in the Cristal mountains, which are projected to lead in the future to the decline of its EOO, AOO, quality of habitat, number of locations, and number of mature individuals. Palisota plicata therefore qualifies as “Endangered” [EN B2ab(i,ii,iii,iv,v)] according to the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Palisota plicata resembles other species with short-trailing stems that are erect at the apex and with axillary inflorescences, such as P. akouangoui , P. cristalensis , P. leewhitei , and P. satabiei , but the plicate nature of the leaves makes it unique in the genus. In fertile condition, P. plicata is also easily distinguished from P. akouangoui and P. satabiei by its mostly erect (rarely pendulous but never decumbent) and strictly unbranched inflorescences. It differs from P. cristalensis by the absence of rusty, erect pubescence on all parts, and from P. leewhitei by the combination of plicate, obovate leaves, longer inflorescences, swollen stems at the insertion of the sheath, and an overall more robust habit. A sterile herbarium specimen collected in Cameroon (Kaji 101) examined at P could represent this species, but in the absence of flowers and fruits, we are not able to assign it there with confidence. Palisota plicata is thus currently unknown from Cameroon, but its presence there would not be surprising.

Paratypi.– EQUATORIAL GUINEA. Prov. Centro Sur : SO du Parc National de Monte Alén , sur le transect Ecofac de Mosuma à 4300 m du début du layon, au sommet de la dernière colline du transect , 01°35'28"N 10°04'17"E, 750 m, 17.III.2001, st., Senterre & Ngomo 896 ( BRLU, MA); Monte Alén PN , près de la piste longeant par le le transect dit de Monte Alén , 01°39'38"N 10°17'36"E, 1200 m, 12.III.2002, fr., Senterre et al. 2807 ( BRLU); N du PN de Monte Alén , à proximité du transect Ecofac de Monte Chocolate , vers 1500 m de l’origine, 01°45'44"N 10°16'29"E, 750 m, 16.XI.2002, fl., Senterre & Ngomo 3457 ( BRLU); N du Parc National de Monte Alén , 2 km au NW du transect Ecofac de Monte Chocolate, vers 1500 m de l’origine, 01°46'09"N 10°15'37"E, 850 m, 25.XI.2002, fl., Senterre & Ngomo 3575 ( BRLU); ibid. loco, 25.XI.2002, fl., Senterre & Ngomo 3576 ( BRLU). GABON. Prov. Estuaire: Monts de Cristal , concession SEEF , en bordure de la Foumana et de la Petite Tsibilé , 00°21'36"N 10°25'35"E, 132 m, 5.XI.2017, fl. & fr., Bidault et al. 3561 ( BR, BRLU, LBV, MO, P); Monts de Cristal, concession SEEF , rive est du Komo , 00°27'00"N 10°39'09"E, 519 m, 3.XI.2017, fr., Bidault et al. 3514 ( BRLU, LBV, MO, P, WAG). Prov. Ngounié: Eteke to Ovala, 01°28'30"S 11°27'18"E, 750 m, 8.XI.1994, fl., Wieringa et al. 3112[B] ( WAG).

Figures

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. 13. – Palisota plicata E.Bidault & Burg. A. Habit; B. Inflorescence; C. Bisexual flower, side view; D. Sepal; E. Petal; F. Lower stamen; G. One upper stamen; H. Ovary and pistil; I. Staminode; J. Mature fruit; K. Immature fruit with exocarp removed, showing immature seeds; L. Sketches of leaf base variation. [A, D-J, L (right): Bidault et al. 3576; B-C, L (left): Bidault et al. 3561; K: Bidault et al. 3514] [Drawings: 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.