Nothodissotis barteri (≡ Dissotis barteri Hook. f.)

Nothodissotis species resemble Dissotis by their 5-merous flowers, calyx with caducous lobes and tube not accrescent on the fruit, presence of intersepalar appendages, dimorphic stamens with the connective bearing bipartite ventral appendages and a well-developed pedoconnective, anthers opening by an introrse apical pore, and cochleate seeds. They differ by being deciduous shrubs (vs. evergreen shrubs and herbs) and having the calyx-lobes notched at apex and asymmetrical (vs. entire and symmetrical); the latter character is unique within African Melastomateae.

Deciduous, ramose shrubs, 1.5–4 m tall; stems 4-angular to cylindrical, glabrous or strigillose; internodes short, nodes setulose or strigillose (Figs 2, 3). Leaves elliptic with appressed hairs on both sides; 3–5-nerved from the base, margins entire or minutely serrulate. Inflorescences terminal, with 1–7(–15) flowers, flowers 5-merous, pedicellate, subtended by a pair of caducous short ovate bracts. Hypanthium broadly urceolate, with scattered appendages, these either sessile and penicillate (N. alenensis; Fig. 2) or stipitate and bearing a stellate crown of hairs at their apex (N. barteri; Figs 2, 3). Intersepalar appendages present, similar to hypanthial appendages but much larger, and caducous (Fig. 2 A–D). Calyx-lobes contorted in aestivation and completely concealing the floral buds, elliptic to obovate, asymmetrically notched and bearing penicillate hairs at apex, uniformly pubescent outside, caducous. Petals mauve, broadly obovate, glabrous except for the ciliate margin. Stamens 10, dimorphic in size but not in colour, pedoconnective well-developed, connective with bipartite ventral appendage, anther falcate, opening by an introrse apical pore. Ovary with a crown of persistent bristles, style simple, linear, glabrous. Fruits capsular, enclosed within the hypanthium, splitting loculicidally in 5 valves, the seeds attached on placentas borne on a central column. Seeds (only known in N. barteri; see Fig. 2 E–H) cochleate, exarillate, with parallel rows of tubercles.

Figure 2. 

Digital microscope photographs of the hypanthia of Nothodissotis spp. (A–D) and SEM photographs of the seeds of N. barteri (E–H). A, B hypanthium of Nothodissotis alenensis (Parmentier & Esono 3453); cl = calyx-lobes and ia = intersepalar appendages C, D hypanthium of N. barteri (Ngok Banak 1196) E, F seeds of N. barteri in dorsal view G, H same in lateral view (Parmentier 3544).

Figure 3. 

Nothodissotis barteri. A habit B branches and inflorescence C leaf seen from above, and flower (petals fallen) D flower bud E blooming flower F stamens. From Droissart et al. 1668 (A, B) and Stévart & Oliveira 5136 (C–F).

Derived from the Greek word ‘nothos’ meaning false, and Dissotis, the genus which Nothodissotis most closely resembles.

Nothodissotis includes two species in Atlantic Central Africa, both of which are restricted to rocky outcrops within the equatorial rainforest zone (Fig. 4).

Figure 4. 

Distribution of Nothodissotis species.

Príncipe, 1859, Barter s.n. (K ! [K000313101]; isolectotype: K ! [K000313102]).

CAMEROON. Réserve de Faune d’Ebo, village de Ndokbaguengue, campement de Djouma, sommet après le transect “Gachaka”, 4°21.7164'N, 10°14.9694'E, 1003 m, 15 Feb. 2014 (fl.), Droissart et al. 1668 (BRLU!, MO!); Ebo forest proposed National park, Ebo Forest Research Station, Bekango trail, 13 Dec 2006 (fl.), Osborne & Emang Abwe 323 (K!). EQUATORIAL GUINEA. Inselberg Acoak Banga près de Ngong Mocomo, 1°04'N, 11°11'E, 8 Aug 1998 (fr.), Lejoly & Elad 98/77 (BRLU!); inselberg de Akoak Ebanga à 1 h du village de Ngong Mocomo, à 10 km de Nsork, 1°04'N, 11°12'E, 585 m, 31 May 2002 (fr.), Parmentier & Esono 3495 (BRLU!); ibid., 590 m, 1 Jun 2002 (fr.), Parmentier & Esono 3544 (BRLU!). GABON. rocher Fané, Efout, E of Médouneu, 5 Feb. 1968 (fl.), N. Hallé & Villiers 4952 (P05264604!); inselberg Milobo, 0°56.35'N, 10°31.31'E, 750 m, 8 Jul 2001 (st.), Ngok Banak et al. 39 (BRLU!, WAG!); ibid., 0°56.35'N, 10°30.94'E, 760 m, 26 Nov 2001 (fl. buds), Ngok Banak et al. 301 (BRLU!, WAG!); ibid., 0°56.29'N, 10°30.87'E, 770 m, 6 Dec 2001 (fl.), Ngok Banak et al. 357 (BRLU!, WAG!); c. 9 km ESE of Médouneu, Efot, inselberg Voma, 1°00.92'N, 10°54.30'E, 500 m, 24 Dec 2002 (fl.), Ngok Banak et al. 1196 (BRLU!, MO!, WAG!); ibid., 1°00.19'N, 10°54.08'E, 523 m, 26 Dec 2002 (fl. & fr.), Ngok Banak et al. 1264 (BRLU!, WAG!); Mont Mengong, inselberg au pied du village de Nzec 1, à 45 km de Mitzic vers Sam, 0°57'N, 11°17'E, 670 m, 6 Jan 2000 (fl), Parmentier & Nguema 585 (BRLU!); Mont Fene, inselberg au pied du village d’Efot, 1°00'N, 10°54'E, 15 Jan 2000 (st.), Parmentier & Nguema 650 (BRLU!); Mont Voma, inselberg au pied du village d’Efot, 1°00'N, 10°54'E, 19 Jan 2000 (fl.), Parmentier & Nguema 745 (BRLU!, WAG!); c. 28 km ESE of Médouneu, 0°55'N, 11°01'E, 500 m, 3 Feb 1986 (fl.), J.M. & B. Reitsma 1796 (WAG!). PRÍNCIPE. Infante D. Henrique, c. 215 m (c. 700 ft), 21 Dec. 1932 (fl.), Exell 652 (BR0000017285346); sommet du Pico, 30 Aug 1999 (fl.), Joffroy 202 (BRLU!); Pico Mesa, 600 m, 25 Mar. 1998 (fr.), Oliveira 546 (BRLU!); Morro Fundao, 1°37'N, 7°23'E, 370 m, 8 Oct. 1997 (fr.), Stévart & Oliveira 259 (BRLU!). Príncipe Island, summit of the Pico de Príncipe, submontane forest with many epiphytes on a ridge, 01°34'48"N, 007°23'01"E, 945 m, 16 Feb. 2018 (fl. & fr.), Stévart & Oliveira 5136 (BRLU!, MO!).

Nothodissotis barteri is sparsely distributed in Cameroon (Ebo forest), south-eastern Equatorial Guinea (near Nsork), northern Gabon, and Príncipe Island (Fig. 4). It occurs exclusively on rock outcrops at 370–1000 m elevation, mainly in low shrubby vegetation near the edge of the rocks (“manteau arbustif”) where it is locally dominant, and sometimes also as isolated plants in rocky grassland dominated by Afrotrilepis pilosa (Boeck.) J.Raynal (Cyperaceae).

Flowering recorded mainly from November–February, once in August; fruits in March, May–June, August, October and December.

Vulnerable [VU B2ab(iii)]. The EOO of Nothodissotis barteri is estimated to be 82,625 km² (above the upper limit for Vulnerable status under sub-criterion B1) and its AOO to be 48 km² (within the limit for Endangered under sub-criterion B2). The species is sparsely distributed in Cameroon, Equatorial Guinea, northern Gabon and Príncipe island, and is restricted to rocky outcrops where it occurs in low shrubby vegetation or grassland. It is known from 21 collections representing eleven subpopulations, most of which (except three on Príncipe island) lie outside protected areas. In most of its range, bushfires and agriculture (mostly pineapple plantations) represent the main threats to its habitat; planned tourism development in Príncipe is another threat. A decline in habitat extent and quality is therefore expected. The eleven subpopulations represent a total of ten locations (sensu IUCN 2012), falling within the limit for Vulnerable status, and the species is therefore assessed as Vulnerable under these conditions B2ab(iii).

This species, originally described from Príncipe Island (Hooker 1871), has since been reported from Gabon (Jacques-Félix 1983b) and Equatorial Guinea (Parmentier and Geerinck 2003). The collections cited above from Cameroon are the first for the country and represent an important range extension northwards.

The seeds of this species have not been described previously (e.g. Jacques-Félix 1983b). They are cochleate, c. 0.5 × 0.35 mm, and bear rounded tubercles arranged in parallel rows (Fig. 2 E–H).

Two specimens, probably from the same field collection by Barter in 1859, are housed in K, with neither of them designated as the holo- or isotype. For this reason, we designate the specimen K000313101 as the lectotype and K000313102 as the isolectotype.

EQUATORIAL GUINEA. Río Muni: Monte Alén National Park, Engong rock slab, 5 km west of Engong village, 1°37'N, 10°18'E, 1100 m, 11 May 2002 (fl & buds), Parmentier & Esono 2763 (holotype: BRLU! [BRLU0000194]; isotype: BRLU! [BRLU0000197]).

This new species differs from N. barteri by its hypanthial appendages that are sessile with penicillate hairs (not stipitate with a crown of stellate hairs) and its more strongly dimorphic stamens, the staminal appendages being much longer in antesepalous stamens than in antepetalous ones (vs. staminal appendages ± equal in length in all stamens).

Deciduous shrub, 1.5–2.5 m tall; stems glabrous except for strigillose pubescence at the nodes; internodes short, 15–80 mm long (Fig. 5A). Leaves simple, opposite, petiole 8–17 mm long with appressed pubescence; blades elliptic, 50–95 × 15–30 mm, base obtuse, apex acute, margins minutely serrulate, hairs appressed on both sides, longitudinal nerves 3(5) from the base, somewhat prominent adaxially, strongly so abaxially and with simple appressed pubescence (Fig. 5B, C). Inflorescence terminal, 1–4 flowered, the flowers 5-merous; pedicels 2–3.5 mm long with strigillose pubescence (Fig. 5D). Bracts 1 pair per flower, at the base of the hypanthium, pubescent outside, 5–8 × 2–5 mm, caducous. Hypanthium broadly campanulate, 8.5–10 mm long, 7–8.5 mm in diameter in fully opened flowers, with scattered sessile appendages bearing simple penicillate hairs, arranged radially and increasing in size from bottom to top. Intersepalar appendages present, elliptic, c. 2 mm long, with short appressed pubescence and a tuft of long hairs at the apex, caducous. Calyx-lobes uniformly pubescent outside, glabrous inside, asymmetrically obovate and notched at apex, 10–15 × 5–8 mm, contorted in aestivation and completely concealing the floral buds, caducous. Petals 26–30 × 30–40 mm, mauve, broadly obovate, glabrous except for the ciliate margin. Stamens 10, dimorphic in size; antesepalous stamens 5, filament 8–12 mm long, pedoconnective 15–18 mm long, curved, ventral appendage bipartite 4–6 mm long, anther falcate, 10–14 mm long; antepetalous stamens 5, filament 7–10 mm long, pedoconnective 3.5–4.5 mm long, ventral appendage bipartite, ca. 1 mm long, anther falcate, 8–13 mm long (Fig. 5E). Ovary with a crown of persistent bristles, style 25–30 mm long, red, glabrous; stigma simple. Fruit and seeds not seen.

Figure 5. 

Nothodissotis alenensis, A habit B, B´ leaf adaxial surface C, C´ leaf abaxial surface D floral buds in different developmental stages; cl = calyx-lobes, ia = intersepalar appendages, p = petals E stamens of the outer (left) and inner (right) stamen whorls (drawn from Parmentier & Esono 1560, 2721, 2763 and 3453). Illustration by Doris Franke.

EQUATORIAL GUINEA. Río Muni: Monte Alén National Park, Monte Alén 2 rock slab, 1°40'N, 10°17'E, 1125 m, 12 Feb 2001 (ster.), Parmentier & Esono 1530 (BRLU0000197!); Monte Alén National Park, Engong rock slab, 5 km west of Engong village, 1°37'N, 10°18'E, 1100 m, 10 May 2002, (fl. buds), Parmentier & Esono 2721 (BRLU0000195!); Monte Alén National Park, Monte Alén 2 rock slab, 1°40'N, 10°17'E, 1110 m, 27 May 2002 (fl.), Parmentier & Esono 3453 (BRLU0000196!).

The species is named alenensis after Monte Alén range and national park in Equatorial Guinea, where it is apparently endemic.

Nothodissotis alenensis is endemic to Monte Alén National Park in Equatorial Guinea (Rio Muni), where it occurs in low shrubby vegetation on rocky outcrops (“manteau arbustif”) at ± 1100 m a.s.l. (Fig. 4).

Flowering in May.

Vulnerable [VU D2]. Nothodissotis alenensis is endemic to Monte Alén National Park in Equatorial Guinea, where it has been collected four times and is known from two rock outcrops, representing two subpopulations. Its EOO cannot be calculated (since only two sites are known) while its AOO is estimated to be 8 km², within the limit for Critically Endangered status under criterion B2. The species occurs in a remote area within a national park, and there is no evidence of an immediate threat or of a population decline. However, its extremely limited range makes it vulnerable to any threat that might arise in the future, e.g. climatic change or introduction of invasive species; it is therefore assessed as Vulnerable according to criterion D2.