Palisota repens 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 : 195-198

7. Palisota repens E. Bidault & Burg , spec. nova ( Fig. 14 , 15A–D ).

Holotypus: GABON. Prov. Ogooué-Lolo: Monts Birougou , Ramsar area , Maranda I village , 20 km S of Pana, 01°46'05"S 12°36'59"E, 715 m, 5.XII.2017, fl., Texier et al. 1437 ( MO [ MO-3047495 ]!; isotype: BR!, BRLU!, LBV!, P!, WAG!).

Palisota repens E. Bidault & Burg most closely resembles P. akouangoui E.Bidault & Burg and P. satabiei Brenan , but differs by the combination of a creeping stem up to 2 m long bearing regularly distributed leaves, and inflorescences that are shorter (compared to P. akouangoui ) and unbranched (unlike in P. satabiei ).

Creeping herb to 0.5– 2 m long, occasionally branched, with apically erect stems ± 4–5 cm tall, in small gregarious subpopulations forming patches of individuals of various sizes. Stems fleshy, wine-red to mauve, woolly white-grayish to rusty pubescent, caducous on the older stems, internodes 2–5(–10) cm long, 2.5–6 mm in diam. in sicco, bearing axillary roots growing through the sheath base, covered with abundant yellow root hairs, never forming a cuff surrounding the sheath and stem. Leaves alternate, regularly distributed along the creeping stem, rarely if ever in an apical pseudoverticil; sheath 11–20 mm long, bent to a 90° angle such that the pseudopetiole is perpendicular to the stem, open for half of its length, occasionally to the swollen base, forming a bulge; pseudopetiole (2–) 4–6 cm long; lamina obovate to obovate-elliptic, (7–)10–18 × 3–6 cm, base long-cuneate, flat to slightly plicate, margins entire, with small, appressed, rusty to ginger-colored trichomes, apex with acumen 5–12 mm long, adaxial surface green to dark green, abaxial surface bright to glaucous green, both surfaces whitish woolly sericeous when young, glabrescent. Inflorescences strictly axillary, rarely geotropic when borne on the apical aerial part of the stem, more often plagiotropic and borne on the creeping portion, 2.5–6(–8) cm long, simple; peduncle 1–3 cm long, with 2–4 persistent peduncular bracts, 8–10(–14) × 3–5 mm, always one at the base of the peduncle, sheathing, acuminate, rusty woolly pubescent to glabrous; the flowering portion with a few more bracts, each subtending a cincinnus, caducous, oblong-lanceolate, pubescent, up to 10 × 5 mm; cincinni sessile or subsessile, with 2– 3 flowers, anthesis sequential, several cincinni often bearing an open flower at the same time. Flowers male and bisexual, 8–10 mm in diam., pedicel 4– 5 mm long, erect at anthesis, becoming spirally contorted after flowering, covered with brown-ochre trichomes, perianth spread at anthesis, then closing again. Sepals equal, oblong, 6 × 2 mm, petaloid, white with dense brown-ochre trichomes on the abaxial surface. Petals similar to sepals, glabrous. Staminodes 3, filaments with long, white, spreading trichomes, antherodes lacking. Stamens 3, unequal, erect, filaments white, the two upper ones with a filament 2–2.5 mm long, glabrous, anthers cylindrical, with a rounded base and apex, 2 × 0.8 mm, sub-basifixed, yellow; the lower stamen more robust, filament of the same length, glabrous, anthers 2.2 × 1.6 mm, pollen sacs slightly curved. Ovary bottle-shaped to ellipsoid, 1 × 0.5 mm, glabrous, style 2.5 mm long, glabrous, white to pale pink, stigma truncate. Fruits irregularly ovoid, slightly oblique berries, weakly triangular in transverse section, dark mauve to black, becoming bright red, 1 × 0.6 cm in sicco, with sparse, thin, erect pubescence, apex acuminate, pedicel spirally contorted, becoming dark purple. Seeds 4, depressed globose, angular, with rounded and slightly flattened sides, ± 2.5 × 3.5 mm, testa smooth, with 20–30 rather faint, flattened ribs, dull dark brown, embryotega round and slightly depressed, the same color as the testa, hilum constricted, wart-like.

Etymology. – The species epithet refers to the distinctive creeping habit of this taxon, which is the only known member of Palisota to be strictly creeping over long distances (up to 2 meters), rooting at the nodes, and with leaves regularly inserted along the stem.

Distribution and ecology. – Palisota repens is known from Gabon, Equatorial Guinea ( Rio Muni) and Republic of Congo (Lékoumou province). In Gabon, it has been collected in Estuaire, Ngounié, Ogooué-Ivindo and Ogooué-Maritime provinces ( Fig. 3 ). It grows in the understory of mature to secondary forests, on slopes, ridges or low areas nearby rivers, but never on inundated ground. It is known from 35 to 1170 m elevation.

Conservation status. – The EOO is 128,388 km ², far exceeding the threshold for “Vulnerable” status under Criterion B1, and the AOO is estimated at 60 km ², within the range for “Endangered” status under Criterion B2. Palisota repens is known from 15 collections, representing 13 sub-populations, 2 of which are situated within the Parque Nacional de Monte Alén in Equatorial Guinea, and one within the MoukalabaDoudou National Park in Gabon, all of which are thought to persist today. The main threats to this species are flooding associated with the construction of hydroelectric projects in the Cristal Mountains, oil exploitation in Rabi (OgoouéMaritime), and forestry in the Cristal Mountains, as well as in Ogooué-Ivindo, Ogooué-Maritime and Ngounié provinces. These sub-populations represent a total of 12 locations with respect to the most important threat (hydroelectric projects), which just exceeds the upper limit for Vulnerable status. Palisota repens therefore qualifies as “Near Threatened” [NT] according to the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Palisota repens resembles shortly creeping species such as P. akouangoui and P. satabiei , but differs in showing long creeping stems up to 2 meters bearing regularly distributed leaves, whereas the latter two taxa have short (up to 40 cm), leafless creeping stem terminating in an erect portion of the axis that bears most of the leaves. Palisota repens can be easily confused with P. akouangoui in the field because they co-occur and have leaves and inflorescences that are very similar on first inspection. To distinguish these two species, as well as P. satabiei , it is necessary to observe and carefully note the habit and phyllotaxy of each plant, and to collect material representing a single habit. Palisota repens can sometimes also be confused with P. plicata: Wieringa et al. 3112 comprises a mixture of material of these two species. One sheet 3112[A] at WAG [WAG.1965281] represents P. repens , whereas another 3112[B] [WAG.1965282] is P. plicata . The type collection, Texier et al. 1437, includes a single open flower photographed and preserved in alcohol that shows a fourth, apparently under-developed stamen, although several other flowers and floral buds were dissected and consistently bore 3 stamens alternating with 3 feathery staminodes, as described above. Although P. repens is known from 15 collections, a very limited number of open flowers are available, as this species has usually been collected with old flowers or fruits. As a consequence, we are not able to determine whether the presence of flowers with 4 (or more) stamens replacing staminodes might represent a second floral type. Until additional material is available and more observations can be made, we have chosen to consider the single observed 4-stamened flower as aberrant.

Paratypi. – EQUATORIAL GUINEA. Prov. Centro Sur : Monte Alén , transecto Monte Alén , 01°39'N 10°18'E, 1170 m, 23.IV.2001, fl., Ngomo 948 ( BRLU); PN de Monte Alén , entre le transect dit de Monte Alén et la Cabaña Bong , 01°39'30"N 10°17'35"E, 1170 m, 7.III.2002, st., Senterre & Obiang 2665 ( BRLU); Parc National de Monte Alén , 11 km à l’E de la Cabaña de Mosumo, 01°36'25"N 10°08'29"E, 615 m, 12.VII.2003, fr., Senterre & Obiang 4138 ( BRLU). Prov. Litoral: Bata , alrededores de Akonikieng , [02°00'N 09°50'E], c. 35 m, 7.II.1992, fl. & fr., Carvalho 5010 ( MA, WAG); Ngoma (10 km SE de Etembue), layon 25, 01°14'N 09°25'E, 42 m, 12.VIII.1998, fl., Lejoly & Elad 98/134 ( BRLU). GABON. Prov. Estuaire: Monts de Cristal , concession SEEF , rive E du Komo , 00°27'00"N 10°39'09"E, 519 m, 3.XI.2017, fl., Bidault et al. 3506 ( LBV, MO); Concession SEEF , rive E du Komo , à 15 km au N du barrage, 00°29'16"N 10°36'00"E, 470 m, 7.XI.2017, y. fr., Bidault et al. 3616 ( BR, BRLU, LBV, MO, P). Prov. Ngounié: Site Ramsar de Birougou , au N de Malinga , entre les villages Leyonga et Mbengamamba , 00°10'45"S 12°10'08"E, 697 m, 21.III.2018, y. fr., Bidault et al. 3981 ( BR, BRLU, G, K, LBV, MA, MO, P, US, WAG); 5 km on road Etéké to Ovala, 01°28'30"S 11°27'18"E, 750 m, 8.XI.1994, fl., Wieringa et al. 3112A ( WAG). Prov. Ogooué-Ivindo: Camp éléphant , 00°15'00"S 12°20'00"E, 300 m, 31.III.2004, fr., Moungazi 1493 ( LBV, WAG). Prov. Ogooué-Maritime: Rabi-Kunga , 01°55'00"S 09°52'00"E, 50 m, 31.V.2002, fl., Bourobou et al. 637 ( LBV); Rabi, 01°55'00"S 09°50'00"E, 60 m, 25.III.1990, fr., Breteler et al. 9509 ( BR, MO, WAG); c. 40 km au NW de Doussala, autour du campement III , 02°14'00"S 10°24'00"E, 450 m, 12.IV.2000, fr., Sosef et al. 1258 ( LBV, MO, WAG). RÉPUBLIQUE DU CONGO. Prov. Lékoumou: Komono , 02°53'16"S 13°36'38"E, 602 m, 1.IV.2009, fr., Cheek et al. 14831 ( P, WAG).

Figures

Fig. 14. – Palisota repens E. Bidault & Burg. A. Habit; B. Inflorescence; C. Bisexual flower; D. Mature fruit; E. Immature fruit; F. Sepal; G. Petal; H. Ovary and pistil; I. Lower stamen; J. One upper stamen; K. Staminode. [A: Bidault et al. 3506; B–C, F–K: Texier et al. 1437; D–E:Bidault et al. 4405] [Drawings: L. Longou]

Fig. 15. – Palisota repens E. Bidault & Burg (A–D) and P. stevartii Burg & E. Bidault (E–G). A. Apical part of creeping stem showing evenly distributed leaves; B. Portion of stem showing curved petiole, root borne in opposition, shortly decumbent inflorescence with closed flowers; C. Immature fruit; D. Inflorescence with two open flowers, the right one being an aberrant 4-stamened flower; E. Detail of inflorescence with cincinni and closed flower; F. Open flower; G. Flowered axis. [A, C: Bidault et al. 3981; B: Bidault et al. 3506; D: N. Texier et al. 1437; E: Stévart et al. 4842; F: Texier et al. 1648; G: Ikabanga et al. 347] [Photos: A–C: E. Bidault; D, F: N. Texier; E: T. Stévart; G: D. Ikabanga]

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.