Nothodissotis alenensis Veranso-Libalah & O. Lachenaud, 2019

Veranso-Libalah, Marie Claire, Lachenaud, Olivier, Stone, Robert Douglas & Kadereit, Gudrun, 2019, Nothodissotis (Melastomataceae), a new genus from Atlantic Central Africa, including the new species N. alenensis from Equatorial Guinea, PhytoKeys 118, pp. 89-103 : 94-97

Nothodissotis alenensis Veranso-Libalah & O. Lachenaud sp. nov. Figs 2A, B ; 5

Type.

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]).

Diagnosis.

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).

Description.

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.

Additional specimens examined.

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!).

Etymology.

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

Distribution and habitat.

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 ).

Phenology.

Flowering in May.

Conservation status.

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 can not 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.

Key to African Melastomateae genera

Figures

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 4. Distribution of Nothodissotis species.

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.