Erythroxylum labatii E.Bidault & M.Pignal, 2022

Bidault, Ehoarn, Traclet, Sébastien & Pignal, Marc, 2022, Novelties in Erythroxylum P. Browne (Erythroxylaceae) from the Comoros Archipelago: two new, range-restricted and threatened species, and notes on the Mount Choungi biogeographical singularity, Adansonia (3) 44 (21), pp. 215-228 : 223

2. Erythroxylum labatii E.Bidault & M.Pignal , sp. nov.

( Figs 3 ; 4 )

E. nossibeensi Baill. similis, sed folia eceracea et paullo revoluta, pedicelli longiores (0.8-1.3 vs 0.35-0.5 cm), et cataphylla glabra, plerumque cum glandula nectarifera (vs papillosa villosa et rare glandula nectarifera) praecipue differt.

TYPUS. — Union of the Comores. Mohéli, Miringoni, Voundrouvou , Chalet Saint Antoine , 660 m, 12°17’17”S, 43°39’50”E, fl., fr., 24.XI.1999, J.-N. Labat, I. Yahaya, E. Daroueche, M. Djoubieri & M. Mindhiri 3212 (holo-, P [ P00184110 ]! ; iso-, CNDRS, MO) .

PARATYPI. — Union of the Comores. Mohéli [Mwali], au-dessus de Drondroni , 688 m, 12°19’06”S, 43°42’39”E, fl., 27.III.2011, E. Bidault, I.Yahaya, G.Viscardi & C. Loup 63 ( HKM; P [ P00852574 ]!]) ; 650 m, 12°19’17”S, 43°42’24”E, fl., 26.III.2011, C. Loup, E. Bidault, I. Yahaya & G. Viscardi 598 ( HKM; MAO; P [ P00852657 ]!) ; centre, forêt du Mont Kimbouana , 700 m, [12°19’30”S, 43°42’45”E], fr., 27.II.1975, J.-J. Floret 1214( P [ P00213746 ]!) ; ouest, ouest du chalet Saint Antoine , 600 m, [12°17’04”S, 43°39’33”E], fr., 28.II.1975, J.-J. Floret 1239, P [ P00213747 ]! ; Mohéli [Mwali], Miringoni, Mdawnyombe , Chalet Saint Antoine , 688 m, 12°17’18”S, 43°39’51”E, fl., 29.V.2006, J.-N. Labat, I. Yahaya & A. Abdou 3734 ( CNDRS; P [ P00527372 ]!]) ; piste entre Miringoni et le chalet Saint Antoine , 610 m, 12°17’24”S, 43°39’43”E, fl., fr., 4.XI.2008, G. Rouhan & M. Pignal 899 ( G; MO; P [ P00684874 ]!) . — Grande Comore [Ngazidja], fl., V.1850, L.H. Boivin s.n. ( P [ P00213749 ]!) ; au-dessus d’Idjikunzi , 885 m, 11°43’56”S, 43°24’48”E, fl., fr., 5.IV.2011, E. Bidault, I. Yahaya, Ramadouane & C. Loup 138 ( HKM; MO; P [ P00852628 ]!) ; Mawéni, massif de la Grille , versant ouest, 1 km est de Maouéni, 800 m, [11°27’52”S, 43°19’55”E], fl., 9.II.1975, J.-J. Floret 814 ( P [ P00213728 ]!) ; 1016 m, 11°28’25”S, 43°20’43”E, fl., fr., 8.VI.2006, J.-N. Labat, I.Yahaya & A. Abdou 3787 ( CNDRS; K; MO; P [ P00527415 ]!) ; versant Est du Karthala, Idjikoundzi , 1301 m, [11°44’12”S, 43°24’25”E], fl., fr., XII.2008, M. Charahabil, M. Chaharmane & M. Younoussa 34 ( CNDRS; P [ P00577868 ]!) ; Gamambili, village Batu , [c. 11°30’00”S, 43°21’40”E], fl., 20.IX.1984, C. Loup 48 ( P [ P00213729 ]!) .

ETYMOLOGY. — The specific epithet honours our friend and colleague Pr. Jean-Noël Labat (1959-2011), who served as Botany team leader at the Muséum national d’Histoire naturelle in Paris. Jean-Noël devoted particular attention to the exploration of the floristic diversity of the Comoros islands and made a very significant contribution to our taxonomic knowledge of several families in the archipelago. He also initiated the programme entitled “ Connaître pour conserver: le patrimoine naturel caché des Comores ” (2008-2011), which allowed him, as well as the first and last authors and numerous colleagues, to gather unique and invaluable data on several groups from the Comoros, and which ultimately led to the establishment of the Comoros National Herbarium, inaugurated in 2011. Finally, Jean-Noël was responsible for more than 4500 high quality collections deposited in the Paris herbarium, with duplicates distributed in collections in Europe and around the world, many associated with field photographs, including the types of this species as well as Erythroxylum choungiense sp. nov., all of which represent an invaluable heritage on which taxonomic work is still being conducted and will likely reveal additional novelties in the years to come.

HABITAT AND DISTRIBUTION. — This species occurs in submontane dense humid forest on ridges, along with Cyathea sp. , palms, and Cynometra sp. on Mwali (fide Labat 3212) and degraded submontane forest with Ocotea sp. , Polyscias sp. , Weinmannia sp. and Olea sp. on Ngazidja (fide Labat 3787), where it is found at altitudes between 600 and 1300 m above sea level.

PHENOLOGY. — Material with flowers and fruits have been collected between February and June, as well as in November and December.

CONSERVATION STATUS. — Erythroxylum labatii sp. nov. occurs on the islands of Mwali and Ngazidja and is known from 13 collections made between 1850 and 2011. Of these 13 collections, only one could not be precisely located (Boivin s.n. from Ngazidja). The 12 remaining collections represent 12 occurrences and two or three extant subpopulations, having been sampled in 2011 (on both Ngazidja and Mwali). While the total number of individuals has not been counted, the population size is estimated to exceed 50 individuals as the label data associated with several collections indicate that the species is common. Using a 2 × 2 km cell size, the AOO of this species is estimated to be 28 km 2 and the EOO is calculated as 429 km 2, both below the upper threshold for “Endangered” status under Red List criteria B2 and B1, respectively. No occurrences are located within protected areas, and they are all threatened by small scale agriculture and deforestation for the production of firewood, largely occurring on both Ngazidja and Mwali. On Mwali, cultivation of crops such as bananas was observed at an elevation of c. 600 m a.s.l. in 2011 (EB pers. obs.) and is presumed to have persisted since then. On Ngazidja, the Massif de la Grille has largely been degraded due to wood harvesting, whereas the Karthala forest is experiencing less pressure from wood harvesting but its extent and quality are still declining due to the same reasons. Moreover, it is not clear whether the absence of collections of this species from below 600 m a.s.l. reflects an ecological preference for higher elevation sites or the fact that most of the forest below this elevation has been severely degraded on both Mwali and Ngazidja. Both of the main threats induce a decline in the quality of the habitat of this species. As a consequence, the 12 occurrences represent 4 locations (sensu IUCN 2012; IUCN Standards and Petitions Committee 2019), with respect to the most serious plausible threat (small-scale agriculture). Based on this threat, we infer a past, current and a future continuing decline in the extent and the quality of its habitat. Erythroxylum labatii sp. nov. is thus assessed as Endangered [EN B1ab(iii)+2ab(iii)].

DESCRIPTION

Slender shrub or small tree to 5.5 m tall, densely branched, with plagiotropic branches. Branches 1.5-3.5 mm in diameter, arranged alternately, silver-brown, finely striated; branches darker when young, with lenticels numerous, elongated, yellowish, 0.5-1.2 mm long, denser and longer on old stems (to 3 mm); internodes 2.5-17 mm long on short branches. Very young portion of stem quadrangular with a rugose yellow face prior to the formation of lenticels. Cataphylls caducous, scarce on the youngest portion of stems, usually by 3-5(7) in the 1-2.5 cm portion of stem above each leaf, distichally arranged, triangular, thick, symmetrical, (1.2-)1.5× 2-2.5 mm, with two conspicuous longitudinal straight wings forming a canalicule, an additional third wing, in between the two main wings, only visible on the apical half, often with a basal median extra-floral nectary, in between the two conspicuous longitudinal wings. Stipules caducous, often present at the base of youngest leaves, 1.5-1.8 × 0.8 mm, asymmetrically triangular, the longest margin to 2 mm, the shortest to 1.2 mm, apex joining the opposite stipule, base thickened, keel winged, straight, margins entire. Petiole 2-3 × 1-1.2 mm, straight, subterete to terete. Leaf blade (43-)58- 74(-90) × (12-)22-28(-36) mm, papyraceous, usually ovate to elliptic, base rounded, margins very slightly revoluted, apex acuminate, acumen straight to curved, (3-) 6-17 mm long, rounded, sometime slightly acute, blade red when immature, discolorous after, dark brown adaxially when dry, light brown abaxially when dry, the midrib slightly prominent at base abaxially, 7-9 secondary veins on each side, most evident on lower leaf surface, forming an angle of (56°-)66°-74°(-86°) with the midrib. Inflorescences a sessile cyme, 1-3(-6)-flowered, borne in the axil of cataphylls in the distal part of the stem; bracteoles triangular, concave, 1 × 0.6-0.7 mm. Flowers: pedicel 9-15 mm. Calyx, 2.1 mm high and 3.8-4.2 mm wide; lobes, 5, 1.8 × 1.1 mm, triangular or rounded, united for about one third to half of their length. Petals white, narrowly obovate, 3.5-5 × 1.7-2 mm, not fully spread at anthesis, slightly constricted at its third, keeled at the upper half; ligule 1.5-2 mm, oriented towards the center of the flower, margin undulate, 2-lobed. Staminal cup smaller than calyx, margin entire. Stamen white, basifix. Short-styled flowers: stamens subequal, 4-4.5 mm long; anthers 0.8 × 0.8 mm, suborbicular, lobate at base; styles 2 mm long, free. Long-styled flowers: stamens subequal, 2-2.2 mm long; anthers 0.5-0.7 × 0.9-1 mm, suborbicular; styles (2-)3, 3.7-4.2 mm, usually fused, sometimes 1 free and 2 attached up to the base of the stigmas. Fruit a drupe, green to bright red with longitudinal darker lines, 9-14 × 5-6 mm when mature and dry, ovoid, pointed at apex, surface smooth; pedicel 11-17 mm long. Seeds not seen.

Figures

FIG. 3. — Erythroxylum labatii E.Bidault & M.Pignal, sp. nov.: A, detail of stem; B, long-styled flower; C, short-styled flower with corolla fallen; D, short-styled flower; E, immature fruit; F, mature fruit; G, habit, dry; H, detail of inflorescence with flower buds; I, detail of cataphyll, abaxial side; A, C, G-I, Labat et al. 3212 (P); B, D, Bidault et al. 63 (P); E, F, Labat et al. 3787 (P). Drawings by Anne-Hélène Paradis. Scale bars: A, B, 2 mm; C, 1 mm; D, 2 mm; E, F, 3 mm; G, 2 cm; H, 2 mm; I, 1 mm.

FIG. 4. — Erythroxylum labatii E.Bidault & M.Pignal, sp. nov.: A, stem and immature fruits; B, inflorescence with flower buds and stem portion with cataphylls; C, long-styled flower; D, mature fruit; E, short-styled flower; A, D, photos by J.-N. Labat, B, E, photos by E. Bidault, C, photo by G. Viscardi.