Palisota cristalensis 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 : 183-186

3. Palisota cristalensis E. Bidault & Burg , spec. nova ( Fig. 6 , 7A–D ).

Holotypus: GABON. Prov. Estuaire: Monts de Cristal , basse-vallée de la Mbé , rive Est , 00°26'18"N 10°17'11"E, 203 m, 28.X.2017, fl., Bidault et al. 3379 ( MO [ MO- 3047497 ]!; isotype: BR!, BRLU!, G [G 00341283 ]!, LBV!, P!, WAG!).

Palisota cristalensis E. Bidault & Burg most closely resembles P. leewhitei Burg, O. Lachenaud & E. Bidault but differs by the combination of a more robust habit, its straight, erect rusty pubescence on the stems, inflorescences, petioles, upper surface of the lamina and primary venation on the lower surface of the lamina, and its erect inflorescence oriented parallel to the petiole.

Creeping and decumbent herb, with erect stems ± 10–20 cm tall, in small gregarious subpopulations forming patches of up to ten individuals of various sizes, covered on all its parts by erect, stiff, rusty to ginger-colored, 3–9 mm long trichomes, except for the glabrous abaxial surface of the lamina. Stems fleshy, internodes 0.5 – 5 cm long, 5 mm in diam. in sicco, light green in vivo, brownish in sicco, bearing axillary roots growing through the sheath base, one of them elongated, glabrous, 1.5 mm in diam., the others short, covered with abundant yellow root hairs, forming a cuff surrounding the sheath and stem. Leaves alternate, spirally arranged along the aerial part of the stem; sheath 7–15 mm long, open for half to four fifths of its length, with brown margins, swollen at the base, forming a whitish-green bulge; pseudopetiole 2.5–5 cm long, bright green; lamina obovate-elliptic to narrowly elliptic, 11–25 × 3–7.5 cm, base acute to cuneate, margins entire, glabrous, adaxial surface green to dark green, abaxial surface lighter green, glabrous except for the primary venation with the same stiff, rusty to ginger-colored trichomes observed on other parts. Inflorescences strictly axillary, borne on the aerial part of the stem, erect, covered by the sheath for about 1.5 cm, then following the axis of the pseudopetiole, occasionally up to the base of the lamina, 4.5– 5 cm long at anthesis, never branched; peduncle 1 –4 cm long, with 2 persistent bracts, sheathing, acuminate, 1 cm long; the flowering portion with 3–6 additional bracts, each subtending a cincinnus, broadly to narrowly ovate, acuminate, 7–15 × 2–6 mm; cincinni sessile, with ± 4 flowers, anthesis sequential, only one flower open at a time per inflorescence. Flowers male and bisexual, 8–8.5 mm in diam., pedicel 12–16 mm long at anthesis, shorter in bud, erect at anthesis, becoming spirally contorted after flowering, perianth spread to sub-reflexed at anthesis, then closing again. Sepals equal, oblong, 6 × 2 mm, petaloid, white with a pale green spot and brown-ochre to purple trichomes at the apex of the abaxial surface. Petals similar to sepals, 6 × 2–2.5 mm, glabrous, white. Staminodes 3, filaments with long white to pale yellow spreading trichomes, antherodes lacking. Stamens 3, unequal, 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, reniform, dorsifixed. Ovary bottle-shaped to ellipsoid, 1 × 0.5 mm, obscurely pubescent, style 1.7 mm long, glabrous, white at base, brown-ochre at the apex, stigma truncate. Fruits irregularly ovoid, slightly oblique berries, weakly triangular in transverse section, green becoming bright red, 15–19 × 9–12 mm in sicco, with sparse, thin, erect rusty trichomes, apex more or less acuminate, pedicel spirally contorted, becoming dark purple. Seeds triangular-ovoid, 3.5 × 3 × 3 mm, shallowly and finely puckered and with numerous (up to ± 40) faint, irregular ribs; operculum/embryotega small, slightly raised, round, hilum minute, in plane with the dark grayish brown testa.

Etymology. – The species epithet refers to the Cristal Mountains in Gabon, where most specimens of this species have been collected.

Distribution and ecology. – Palisota cristalensis is known from Gabon (Estuaire and Woleu-Ntem provinces) and Equatorial Guinea ( Rio Muni). Most specimens (8) have been collected in the Cristal Mountains in Gabon, one came from the Ndote Reserve in Equatorial Guinea, and one is known from south of the Komo river, near the Remboué river ( Fig. 5 ). It grows in the understory of mature to secondary forests on terra firme, on slopes and nearby rivers, but not on inundated ground. It is known from 40 to 555 m elevation.

Conservation status. – The EOO is 6,320 km ², above the upper threshold for “Endangered” status under Criterion B1, and the AOO is estimated at 32 km ², at lower end of the range for “Endangered” status under Criterion B2. Palisota cristalensis is known from 10 collections, 8 of which were made in the Cristal Mountains, both inside and outside the National Park (Mbé sector), near the Kinguélé and Tchimbélé hydroelectric dams on the Mbé river, all after the completion of dam construction. One collection was gathered at an oil exploitation concession in 1991 near the Remboué river, south of the Komo river, in Estuaire province, and another one was made in the Ndote Reserve in Equatorial Guinea in 1998. These 11 collections represent 4 sub-populations. The sub-population located at the Remboué drilling site is threatened by oil exploitation, and that located near Kinguélé in the Mbé valley in Cristal Mountains, though situated in the National Park, is threatened by the planned development of a hydroelectric dam on the Mbé river, which is expected to lead to its extirpation. Despite being located outside the National Park, there is no evidence of an existing threat to the subpopulation located near Tchimbélé in the Cristal Mountains. The 4 sub-populations represent 4 locations with respect to the most important threat (hydroelectric projects). This species is threatened by oil exploitation and the development of a hydroelectric project, leading to projected decline of its EOO, AOO, quality of its habitat, number of locations and number of mature individuals. Palisota cristalensis therefore qualifies as “Endangered” [EN B2ab(i,ii,iii,iv,v)] according to the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Despite its abundance in the Cristal Mountains, where 8 specimens were collected starting thirty years ago, P. cristalensis has never been recognized as separate from P. satabiei . This is probably due to the morphologically broad description of P. satabiei provided by BRENAN (1984) and to his inclusion of Hallé & Villiers 5310 from the Cristal Mountains, described as having profuse long, patent rusty trichomes on the petiole, leaf margins and upper side of the lamina, a collection that we have not located at P, but which we suspect could be of P. cristalensis . Nevertheless, P. cristalensis differs from P. satabiei by its short, erect inflorescence, and its peculiar pubescence, which we now know does not fall within the range of variation of P. satabiei . Palisota cristalensis more closely resembles P. leewhitei by its habit and short, erect inflorescence bearing sessile cincinni, but can be easily distinguished from it by its pubescence and an overall more robust habit.

Paratypi – EQUATORIAL GUINEA. Prov. Litoral: Ndote AP , rte forestière Engong - [?], 01°25'00"N 09°32'00"E, 40 m, 37. VII.1998, st., Lejoly & van Asbroek 32 ( BRLU). GABON. Prov. Estuaire: Monts de Cristal , Kinguélé , basse-vallée de la Mbé , 00°25'13"N 10°15'26"E, 96 m, 26.X.2017, fl., Bidault et al. 3309 ( BR, BRLU, LBV, MO, P, WAG); Parc des Monts de Cristal , vers le pont de Kinguélé , 00°28'07"N 10°16'36"E, 120 m, 5.XI.2015, fl., Boupoya & Issembé 1159 ( LBV, MO); Plateforme de forage Remboué 1 , 00°13'00"S 10°02'00"E, 40 m, 21.I.1991, fl., Louis & Moungazi 3288 ( LBV, MO); side road at km 46 of road from Kougouleu to Méla, just within PN Monts de Cristal , 00°36'18"N 10°20'12"E, 104 m, 21.XI.2011, fl., Maas et al. 10428 ( WAG); Cristal Mountains, 1 km W of Tchimbélé, 00°37'00"N 10°24'00"E, 450 m, 16.XII.1989, fl., Wieringa 234 ( LBV, MO, WAG); 1 km WNW of Tchimbélé, on the bank of Bingiligwen river , 00°37'00"N 10°23'00"E, 460 m, 12.V.1990, fr., Wieringa 904 ( LBV, WAG). Prov. Woleu-Ntem: Cristal Mountain , 00°36'00"N 10°24'00"E, 500 m, 15.XI.2000, y. fr., Nguema Miyono 1335 ( LBV, MO, WAG); 3 km from hydroelectric compound at Tchimbélé, 00°37'54"N 10°23'25"E, 555 m, 14.XI.2002, fl., Strijk 346 ( LBV, MO, WAG).

Figures

Fig. 6. – Palisota cristalensis E. Bidault & Burg. A. Habit; B. Inflorescence; C. Portion of stem with inflorescence; D. Bisexual flower from above; E. Bisexual flower, side view; F. Sepal; G. Petal; H. Lower stamen; I. One upper stamen; J. Staminode; K. Ovary and pistil. [A, D-K: Bidault et al. 3379; B-C: Bidault et al. 3309] [Drawings: L. Longou]

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. 5. – Distribution of Palisota cristalensis E. Bidault & Burg (stars) and P. alboanthera Burg & E. Bidault (triangles). Elevation is represented in levels of grey, and protected areas as shaded.