Palisota akouangoui 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 : 176-180

1. Palisota akouangoui E. Bidault & Burg , spec. nova ( Fig. 1 , 2A–C ).

Holotypus: GABON. Prov. Ngounié: Site Ramsar de Birougou , au N de Malinga , autour du village Moukembi , 02°02'36"S 12°10'01"E, 729 m, 25.III.2018, fr., Bidault et al. 4100 ( MO [ MO-3047498 ]!; isotype: BR!, BRLU!, G [ G00341282 ]!, K!, LBV!, LISC!, MA!, NY!, P!, US!, WAG!).

Palisota akouangoui E. Bidault & Burg most closely resembles P. satabiei Brenan but differs by its strictly unbranched, longpeduncled inflorescence comprising a thyrse composed of multiple cincinni bearing flowers with unequal stamens, the lower of which is larger.

Creeping and decumbent herb to 20– 40 cm long (rarely longer), with erect stems 5 –12 cm tall, in small gregarious subpopulations forming patches of individuals of various sizes. Stems white woolly pubescent at the apex, glabrescent, internodes to 2 cm long, 6–10 mm in diam. in sicco, brown to mauve in vivo, brownish in sicco, bearing profuse axillary roots, a few 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 to pseudowhorled at the apex, absent or rarely present on the creeping part of the stem; sheath up to 3 cm long, long-attenuate on the pseudopetiole, open for a quarter to a third of its length, not swollen at the base; pseudopetiole 3–9 cm long, appressed white woolly pubescent, glabrescent, green to purple; lamina obovate-elliptic to spathulate, 11–25 × 4–9 cm, base narrowly cuneate, margins entire, with small appressed ginger-colored trichomes, apex rounded to obtuse-apiculate, white woolly pubescent on both surfaces when young, glabrescent, adaxial surface green to dark green, abaxial surface slightly lighter green, with prominent, green to purple primary venation. Inflorescences strictly axillary, borne on the aerial part of the stem, decumbent, 4–23 cm long, never branched, even in fruit, elongating as they mature; peduncle 3–20 cm long, woolly pubescent, glabrescent, pale green at anthesis, turning dark purple to black, with (2–)3 persistent bracts, 1.3–2 cm long, sheathing, acuminate, densely covered by rusty trichomes, glabrescent; the flowering portion of the inflorescence in a compact thyrse at anthesis, elongating as it matures, occasionally with a cuff of short roots with abundant white to yellow root hairs at the fruiting stage; thyrse ± 1.5 cm long at anthesis, to ± 3 cm long in fruit, with 4–5 bracts initially forming a pseudo-whorl at the base, later each subtending a cincinnus, caducous, narrowly triangular, 8 –11 × 1.5–2 mm, with erect, rusty trichomes, more dense at the apex; cincinni 3–5, 1– 3 mm long, with 3(–4) flowers, anthesis sequential, several cincinni often bearing an open flower at the same time. Flowers male and bisexual on the same inflorescence, buds pale pink at base, white elsewhere except the pale green apex, flowers 4–5 mm in diam., pedicel 1 cm long at anthesis, erect, becoming spirally contorted after flowering, perianth spread to reflexed at anthesis, then closing again. Sepals equal, oblong, apically concave, 5 × 2 mm, petaloid, transparent white with a greenish spot at the apex, with short, erect, white to brown trichomes on the abaxial surface, more dense at the apex. Petals similar to sepals, white, glabrous. Staminodes 3, filaments with long, white, spreading, moniliform trichomes, antherodes lacking. Stamens 3, unequal, erect, the two upper ones with a white filament 2–2.5 mm long, glabrous, anthers oblong, rounded, not curved, 0.8 × 0.5 mm, basifixed, yellow; the lower stamen more robust, filament white, 2.5–3 mm long, glabrous, anthers 1.2 × 0.6 mm, larger at the apex, sub-basifixed, pollen sacs slightly curved, pale yellow, becoming green after dehiscence. Ovary bottle-shaped to ellipsoid, 1.5 × 0.8 mm, with a few stiff trichomes, style 2.2 mm long, glabrous, white, curved at the apex, stigma truncate. Fruits usually borne above the litter, occasionally below, ovoid to ovoid-oblong berries, apex acute to clearly acuminate, 12–17 × 4–10 mm in sicco, beigepink to brown-green when young, becoming bright red, with sparse, long, appressed pubescence, pedicel spirally contorted, becoming dark purple. Seeds depressed globose, with rounded and slightly flattened sides, ± 3.5 mm in diam., black in vivo, brownish grey in sicco due to the thin, pale brown, transparent arilloid that forms a skin, testa beneath smooth, with 20–30 very faint, flattened ribs surrounding the seed, shiny black, embryotega depressed, dark gray, hilum wart-like.

Etymology. – The species epithet honors Eric Akouangou, technician and field botanist at the Herbier National du Gabon [LBV], part of the Institut de Pharmacopée et de Médecine Traditionnelle [IPHAMETRA] of the Centre National de la Recherche Scientifique et Technologique [CENAREST]. In addition to co-managing a large collection of living orchids maintained in Libreville, he has been a co-collector of herbarium material comprising more than 7,500 numbers made in Gabon (7.5 % of all collections from the country), including the type of this species. His jovial character, dedication to fieldwork and professionalism make him an important and efficient collaborator. Eric is thus acknowledged for his remarkable contribution to the knowledge of the Gabonese flora.

Distribution and ecology. – Palisota akouangoui is known from Cameroon (South province), Equatorial Guinea (Centro Sur), Gabon (7 provinces), and the Republic of Congo (Kouilou province) ( Fig. 3 ). It grows in the understory of mature to secondary forests on terra firme, on slopes, ridges or near rivulets where the vegetation is not inundated. It is known from 10 to 850 m elevation.

Conservation status. – The EOO is 192,081 km ², exceeding the threshold for “Vulnerable” under Criterion B1, and the AOO is estimated at 72 km ², which is below the threshold for “Endangered” status under Criterion B2. Palisota akouangoui is known from 21 collections that represent 16 sub-populations, 3 of which are situated in protected areas, viz. Parc National des Monts de Cristal in Gabon, and Parque Nacional de Monte Alén in Equatorial Guinea. The main threat to this species are flooding associated with hydroelectric projets proposed on the Louétsi river in Ngounié province, oil exploitation in Rabi (Ogooué-Maritime), and forestry (Ogooué-Lolo, Woleu-Ntem, Estuaire and Nyanga provinces in Gabon, and Kouilou region in Congo). These sub-populations represent a total of 14 locations with respect to the most important threat (hydroelectric projects), which exceeds the upper limit for Vulnerable status. Palisota akouangoui therefore qualifies as “Least Concern” [LC] according to the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – The character of the lower anther becoming green after dehiscence of the pollen sacs has been observed in a single recent collection of P. akouangoui (Bidault et al. 3785), which was collected and photographed at the required developmental stage. We cannot, however, confirm whether this character is constant within the species, but material has been collected at this stage of the anther development from two other species (Bidault et al. 3717 for P. bogneri, Texier et al. 1437 for P. repens ), none of which shows as green coloration of the anther, which instead remains yellow. The occasional presence of a radicant cuff surrounding the infrutescence, which has sometimes been found under the leaf litter suggests possible vivipary and stoloniferous behavior. While vivipary has not yet been directly observed in P. akouangoui , it has been observed in P. flagelliflora ( FADEN, 1995) . Palisota akouangoui resembles P. bogneri , P. flagelliflora , P. repens and P. satabiei , but can be distinguished from them by the combination of a shortly creeping habit, an unbranched, decumbent inflorescence, and unequal stamens, the lower one being more robust and becoming green after dehiscence of the pollen sacs. In addition to being a strictly rosette species, P. flagelliflora is characterized by long, creeping, flagelliform inflorescences bearing solitary cincinni; P. bogneri differs in having subequal, consistently yellow stamens. By its shortly creeping habit, P. akouangoui can be easily distinguished from P. repens , which is a long-creeping species, up to 2 m long, with leaves evenly distributed along the stem. Palisota akouangoui most closely resembles P. satabiei , with which it has historically been confused, but the latter has branched inflorescences, which is a robust structural character that is never found in P. akouangoui , which bears compact, (sub-)globose inflorescences on a rather stout peduncle. Two collections cited as paratypes in the protologue of P. satabiei (viz. Satabie & Letouzey 384 and 407) in fact represent material of P. akouangoui , as indicated by the presence of multiple cincinni on the unbranched inflorescence, whereas P. satabiei has solitary cincinni on each ramification of its inflorescence. In the field, P. akouangoui and P. bogneri often grow together and have occasionally been gathered under the same collection number. For example, Schoenmaker 277 comprises two sheets deposited at WAG [WAG.1488450, WAG.1952609] that represent P. bogneri , whereas the specimen deposited at LBV [LBV0035326] clearly represents P. akouangoui , as indicated by the presence of an evident stem. Similarly, most material of Bidault 1969 represents P. bogneri , but the sheet at BRLU is of P. akouangoui . A few collections examined could not be assigned with certainty to either one of these species. For instance, Nguema 2879 could represent P. bogneri as it is apparently almost stemless, while it might instead belong to P. akouangoui due to its slightly elongated thyrse, but because the base of the plant is missing on every sheet, we were unable to provide a definitive identification.

Paratypi. – CAMEROON. Reg. South: Massif de Ngovayang , 18 km W de Lolodorf, 03°16'00"N 10°34'00"E, 850 m, 3.II.1979, fl., Satabié & Letouzey 384 ( P); ibid. loco, 3.II.1979, fl., Satabié & Letouzey 407 ( P). EQUATORIAL GUINEA. Prov. Centro Sur : SE du Parc National de Monte Alén , au N du Rio Laña , près de la Cabaña Ecofac de Misergue , 01°26'11"N 10°13'09"E, 530 m, 29.I.2002, fl., Senterre et al. 2102 ( BRLU); SW du PN de Monte Alén , 2 km au NE du site de traversée du Rio Uolo pour aller au cataractas, 01°36'36"N 10°05'47"E, 800 m, 27.VI.2002, fr., Senterre & Nguema 3091 ( 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, y. fr., Bidault et al. 3563 ( BR, BRLU, G, LBV, MO, P, WAG); Song, 29525 m on Transect F , 00°51'00"N 10°12'00"E, 335 m, 23.II.2001, fr., Mayombo-Nzengue 436 ( LBV, WAG). Prov. Moyen-Ogooué: 5–30 km NNW of Ndjolé, 00°05'00"S 10°45'00"E, 240 m, 23.IV.1992, fr., Breteler et al. 11054 ( WAG). Prov. Ngounié: Dibwangui , bords de la Louétsi , 02°06'45"S 11°35' 07"E, 391 m, 13.XI.2017, fl., Bidault et al. 3687 ( BR, BRLU, LBV, MO, P); rte entre Dibwangui et Lebamba , 02°10'00"S 11°34'53"E, 360 m, 16.XI.2017, fl., Bidault et al. 3785 ( BR, BRLU, G, LBV, MO, P, WAG); Site Ramsar de Birougou , au N de Malinga , autour du village Mbengamamba , 02°09'48"S 12°10'25"E, 719 m, 23.III.2018, y. fr., Bidault et al. 4065 ( LBV, MO, P); 50 km SE of Lambaréné, 01°04'00"S 10°30'00"E, 155 m, 30.IX.1968, fl., Breteler 5751 ( WAG). Prov. Nyanga: 22 km along the road from Mayumba to Tchibanga, and then about 10 km along a forest exploitation track in an E direction, near the Doussa river , 03°16'00"S 10°45'00"E, 10 m, 7.XII.1986, fl., de Wilde et al. 9205B ( MO, WAG). Prov. Ogooué-Lolo: Concession forestière SEEF , au SE du PN de l’Ivindo , à 80 km au NE de Lastoursville, 00°15'32"S 13°14'04"E, 527 m, 17.X.2015, fl., Bidault et al. 1969B ( BRLU); c. 25 km on the road Lastoursville – Koulamoutou, 00°58'18"S 12°34'36"E, 250 m, 25.X.2005, fl., Sosef et al. 2082 ( LBV). Prov. Ogooué-Maritime: Rabi Kunga , 01°55'00"S 09°52'00"E, 50 m, 11.III.2002, fr., Bourobou et al. 570 ( LBV, WAG); ibid. loco, 01°58'00"S 09°54'00"E, 65 m, 5.XII.1991, fl., Schoenmaker 277B ( LBV). Prov. WoleuNtem: Chantier Rougier Océan , Oveng , c. 25 km SW of Mintsic, 00°44'00"N 11°22'00"E, 590 m, 20.IX.1985, fl., Reitsma & Reitsma 1495 ( LBV); ibid. loco, 6.XI.1986, fl., Reitsma et al. 2516 ( LBV). REPUBLIC OF CONGO. Prov. Kouilou: Les Saras , piste Cofibois de Condé , 04°24'00"S 12°21'00"E, 200 m, 9.II.1988, fr., de Foresta 1563 ( P).

Figures

Fig. 1. – Palisota akouangoui E. Bidault & Burg. A. Habit; B. Mature fruit; C. Inflorescence; D. Bisexual flower; E. Sepal; F. Petal; G. Lower stamen; H. One upper stamen; I. Staminode; J. Ovary and pistil. [A: Bidault et al. 3687; B: Bidault et al. 4100; C-J: Bidault et al. 3785] [Drawings: D. Geffard-Kuriyama & L. Longou]

Fig. 2. – Palisota akouangoui E. Bidault & Burg (A–C) and P. alboanthera Burg & E. Bidault (D–G). A. Entire plants showing infrutescences; B. Mature fruits, entire and opened, showing seeds; C. Inflorescence showing open flowers, with green lower stamen; D. Living plant with inflorescence; E. Young inflorescence with male flowers, showing erect, pale yellow lower stamen; F. Bisexual flower with reflexed, white lower stamen; G. Detail of swollen roots. [A–B: Bidault et al. 4100; C: Bidault et al. 3785; D–F: Bidault et al. 3807; G: Stévart et al. 4780] [Photos: E. Bidault]

Fig. 3. – Distribution of Palisota akouangoui E. Bidault & Burg (squares) and P. repens E. Bidault & Burg (circles). Elevation is represented in levels of grey, and protected areas as shaded.