Friday, March 8, 2019

[Botany • 2019] Nothodissotis (Melastomataceae) • A New Genus from Atlantic Central Africa, including the New Species N. alenensis from Equatorial Guinea

Nothodissotis barteri (Hook.f.) Veranso-Libalah & G.Kadereit

in Veranso-Libalah, Lachenaud, Stone & Kadereit, 2019.

Based on morphological and phylogenetic evidence, a new genus of Melastomataceae (Melastomateae), Nothodissotis Veranso-Libalah & G.Kadereit, gen. nov., is described from Atlantic Central Africa. Nothodissotis is distinguished from other African Melastomateae genera by its calyx-lobes that are notched at apex and asymmetrical (vs. entire and symmetrical). Nothodissotis includes two species: the type species N. barteri (Hook.f.) Veranso-Libalah & G.Kadereit, comb. nov. (syn. Dissotis barteri Hook.f.), and the new species N. alenensis Veranso-Libalah & O. Lachenaud, sp. nov., described and illustrated here. Both species are restricted to open vegetation on rock outcrops within the forested region of Atlantic Central Africa. Nothodissotis barteri has a scattered distribution in Cameroon, Equatorial Guinea, Gabon and Príncipe Island, while N. alenensis is endemic to the Monte Alén massif in Equatorial Guinea, an area where N. barteri does not occur. Nothodissotis alenensis differs from N. barteri by its hypanthium bearing sessile appendages with penicillate hairs (vs. stalked stellate appendages) and its staminal appendages that are much smaller in antepetalous than in antesepalous stamens (vs. subequal in all stamens). The conservation status of both N. barteri and N. alenensis is assessed as Vulnerable in accordance with IUCN criteria.

Keywords: Africa, morphology, Dissotis, Equatorial Guinea, Melastomataceae, new species, Nothodissotis, phylogeny, plant conservation, vulnerable species

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).

Nothodissotis Veranso-Libalah & G.Kadereit, gen. nov.

Type: Nothodissotis barteri (≡ Dissotis barteri Hook. f.)

Morphological diagnosis: 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.

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

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

Nothodissotis barteri (Hook.f.) Veranso-Libalah & G.Kadereit, comb. nov. 
Dissotis barteri Hook.f., Fl. Trop. Afr. [Oliver et al.] 2: 454 (1871).


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.

Nothodissotis alenensis Veranso-Libalah & O. Lachenaud, sp. nov.

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).

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).

 Marie Claire Veranso-Libalah, Olivier Lachenaud, Robert Douglas Stone and Gudrun Kadereit. 2019. Nothodissotis (Melastomataceae), A New Genus from Atlantic Central Africa, including the New Species N. alenensis from Equatorial Guinea. PhytoKeys. 118: 89-103. DOI: 10.3897/phytokeys.118.31572

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