Dalbergia obcordata N. Wilding, Phillipson & Crameri, 2021

Wilding, Nicholas, Phillipson, Peter B., Crameri, Simon, Andriambololonera, Sylvie, Andriamiarisoa, Roger L., Andrianarivelo, Sandratra A. F., Bernard, Roger, Rakotonirina, Nivo, Rakotovao, Charles, Randrianaivo, Richard I., Razakamalala, Richard & Lowry Ii, Porter P., 2021, Taxonomic studies on Malagasy Dalbergia (Fabaceae). I. Two new species from northern Madagascar, and an emended description for D. manongarivensis, Candollea 76 (2), pp. 237-249 : 246-248

Dalbergia obcordata N. Wilding, Phillipson & Crameri , sp. nov. ( Fig. 5, 6 ).

H o l o t y p u s: M A DA G A S C A R. R e g. S AVA [Pr o v. Antsiranana]: Daraina, forêt de Solaniampilana-Maroadabo , 13°05'19"S 49°35'05"E, 140 m, 6.III.2004, fl., Gautier, Wohlhauser, Nusbaumer & Ranirison 4567 ( G [ G0006697 ] image!; iso-: P [ P02890651 ]!, TEF) .

Dalbergia obcordata N. Wilding, Phillipson & Crameri most closely resembles D. gautieri Bosser & R. Rabev. from northern Madagascar in possessing leaflets of a similar size, shape and number per leaf, but differs by having inflorescences that are lax, sparsely-branched panicles (vs. short, dense, corymbiform panicles with secundiflorous terminal axes in D. gautieri ).

Shrubs or sprawling shrubs to 6 m tall. Branches pubescent, reddish-brown in vivo (grey in sicco) when young, becoming glabrous, pale grey-brown when old, lenticels present. Leaves alternate, (4–)5–9(–10.5) cm long, with 5–8 alternate leaflets; petiole and rachis pale yellow-green in vivo, dark brown to black in sicco, sparsely white to yellowish-pubescent, glabrescent; petiole 9– 15 mm long; stipules early caducous (none seen on available specimens), leaving a visible scar; leaflets (14–)20– 41 × 8– 18 mm, the proximal leaflets smaller than the rest, the distal leaflet equal to or slightly larger; petiolule 1.5 –2.5 mm long, pale yellow-green in vivo, dark brown to black in sicco, sparsely white to yellowish-pubescent, glabrescent; lamina obcordate, rarely obovate or oblong-obovate, coriaceous, base cuneate or rounded in smaller leaflets, margin plane to slightly revolute, apex weakly to strongly retuse or less often rounded, venation eucamptodromous, with 6–10 principal lateral veins per side; upper and lower surface mid-green in vivo, red-brown to dark brown in sicco, upper surface glossy, glabrous to weakly pubescent along the proximal half of the midrib, midrib forming a groove, lower surface matt, glabrous, higher-order veins forming a fine network, midrib prominent. Inflorescences terminal or axillary, a panicle, 5.5–13 cm long, composed of sparsely-branched paniculate units decreasing in size towards the apex, the basal and apical units with oblong, scale-like bracts, 3.5– 4 × 1 mm, distal portions racemose, axes glabrous; peduncle to 2 cm long. Flowers subtended by a caducous bract (none seen), leaving visible scar; pedicel

1 mm

H. Calyx (outer surface; split open and flattened); I. Androecium (split open to show adaxial surface); J. Gynoecium.

[Gautier et al. 4567, P] [Drawings: M. Lanas]

1.6–2.6 mm long, glabrous or weakly puberulous; bracteoles obovate, 1.5–1.7 × 7–8 mm, apex rounded, glabrous, red-brown in sicco, caducous; calyx pale yellow-green in vivo, becoming black to orange or yellow in sicco, glabrous except for minutely ciliate apices of lower three lobes, possibly persisting on fruits, 4–4.5 mm long, fused in the lower 2/3, the 2 upper lobes fused to form a single, rounded unit, c. 1.5 × 3 mm, apex deeply notched, the 2 lateral lobes obtuse, c. 2 × 1.3 mm, the lowest lobe acute, keeled, c. 2 × 1.5 mm; petals glabrous, white (with green tints near the base) to yellow-cream in vivo (Gautier et al. 4567; Fig. 6 ), becoming yellow to orange in sicco; standard petal orbicular, 3.8–4.2 × 3–3.3 mm, claw c. 1 mm long, apex notched; wing petals 3.6–3.9 × 1.7 mm, claw c. 1.5 mm long; keel petals 3.6–3.9 × 2 mm, claw c. 1 mm long; androecium glabrous, monadelphous, 3.5–4 mm long; stamens 9 or 10, filaments free for upper 1/2–3/5; gynoecium 3–4 mm long, glabrous; stipe 1–1.5 mm long; ovary c. 1 mm long, with 1 or 2 ovules; style 1 –1.3 mm long. Mature fruits unknown, young fruits green, margins and stipe red in vivo.

Etymology. – Dalbergia obcordata is named for its distinctive obcordate leaflet laminae, an unusual shape among Malagasy members of the genus.

Distribution, ecology and phenology. – Dalbergia obcordata is restricted to a small area in extreme northeastern Madagascar. It is known from only two localities, the Antsahabe and Solianampilana-Maroadabo forests, about 10.5 km apart, in the surroundings of Daraina in the SAVA region. It occurs at low elevation in dry forest.

Flowering has been recorded in March and May.

Conservation status. – Dalbergia obcordata is only known from two recent collections, from sites 10.5 km apart, each in a separate forest patch within the Loky-Manambato Protected Landscape, resulting in an AOO of 8 km ² (based on 4 km ² grid). Its presence in a Protected Landscape (IUCN category V), where human activity is permitted, does not afford the same level of protection as in IUCN category I–IV protected areas, where exploitation is strictly prohibited or controlled. Dalbergia obcordata is therefore at risk locally from habitat loss linked to ongoing forest clearing for agriculture and wild fires. Each of the two known subpopulations represents a separate location with respect to the most serious plausible threat of habitat loss and therefore D. obcordata is assigned a preliminary conservation status of “Endangered” [EN B2ab(ii,iii,iv,v)] following the IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – Phylogenomic and population genomic results ( CRAMERI, 2020) support the recognition of Dalbergia obcordata as a distinct species and point to only a distant

[Gautier et al. 4567] [Photo: L. Gautier]

relationship with D. gautieri (a Group 2 species), with which it bears some similarity (see diagnosis above).

While only immature fruits of Dalbergia obcordata are known, members of species of Group 1 generally possess fruits with a smooth pericarp that are oblong-elliptical and reddish-brown. The species is suspected to be deciduous, like other members of Group 1.

Paratypus. – MADAGASCAR. Reg. SAVA [Prov. Antsiranana]: Daraina, forêt d’Antsahabe , 13°10'51"S 49°33'13"E, 415 m, 1. V .2004, fl., y.fr., Ranirison 758 ( G [ G00028112 ], P [ P02890655 ], TAN) .

Figures

Fig.6. – Dalbergia obcordata N. Wilding, Phillipson & Crameri. Inflorescence and leaflets.