Lijndenia darainensis R.D. Stone, 2017

Stone, R. Douglas, 2017, Revised treatment of the genus Lijndenia (Melastomataceae, Olisbeoideae) in Madagascar, Candollea 72 (1), pp. 67-86 : 75-76

3. Lijndenia darainensis R.D. Stone , spec. nova ( Fig. 4 A-B, 5).

Typus: MADAGASCAR. Prov . Antsiranana: Daraina region , forêt de Binara, 13°16’19”S, 49°35’59”E, 29.XI.2006, fl., Gautier & Chatelain 4951 (holo-: G [ G00340058 ]!; iso-: CAS-1104864!, MO, P, TEF, Herb. Darainense) .

Affinis L. danguyanae (H. Perrier) Jacq. -Fél. sed laminis foliorum parvioribus (3-5 X 1.5-3 cm non 5-13 X 2.5-6 cm) ut videtur uninervis (non conspicue trinervis), nervis lateralibus invalidis intramarginalibus differt.

Tree 20 m, the trunk with diameter 40 cm at breast height; branchlets with whitish gray bark, the youngest compressed and longitudinally grooved on the two faces, with age becoming terete, stout and thickened at the defoliated nodes; internodes (0.5-)1-2.5(-4) cm. Leaves apparently 1-nerved (midnerve clearly visible, finely impressed on the upper surface, somewhat prominent on the lower; lateral nerves percurrent but only faintly visible, situated 1-2 mm from the revolute margins), subcoriaceous, finely granular in dried material; petioles 2.5-5 mm; blades elliptic to obovate, 3-5 X 1.5-3 cm, cuneate at the base, attenuate and decurrent on the petiole, rounded and ± retuse at the apex; transverse veins scarcely visible, 4-5 pairs spaced 4-6 mm apart, somewhat oblique relative to the midnerve. Cymes umbelliform and 3-7-flowered, in fascicles of 1-4 at the leafless nodes of older branchlets, subsessile or with peduncle c. 1 mm; bracts not evident; individual flowers subtended by a pair of persistent, truncate-suborbicular bracteoles c. 0.25 mm forming a cupule or involucre from which emerges the pedicel 4- 7.5 mm. Hypantho-calyx cupulo-patellate, 3 X 3 mm, the margin shallowly sinuate to truncate and remotely 4-denticulate; corolla rounded in bud, white, the style long-exserted, pale violet; petals at anthesis pale violet with white margins, 2 X 2.5 mm, unguiculate-hastate with a pair of rounded to pointed lobes 0.3 mm situated about halfway between the base and the apex, the apex broadly rounded and shallowly cucullate, with a pair of auricles 0.6-0.75 mm at the base of the limb, the claw 0.5 X 0.25 mm; staminal filaments 3-6 mm (the epipetalous filaments noticeably longer than the episepalous ones), pale violet; anthers 1.75 mm, thecae fronto-ventral, yellow; connective white, incurved by the median dorsal oilgland 0.3 mm, extremity conical-acute; style slender, 10 mm, pale violet. Fruits not seen.

Etymology. – The species epithet refers to the Daraina region of northeastern Madagascar, which in the last two decades has been the subject of much biological research and conservation interest (including extensive plant collecting by Dr. L. Gautier and colleagues of the Conservatoire et Jardin botaniques de la Ville de Genève).

Distribution and ecology. – The type and only known locality of L. darainensis is in the Binara forest (Daraina region, Antsiranana Province) at elevation 920 m ( Fig. 3 ). This species and L. danguyana are the only two Madagascan Lijndenias inhabiting montane forest, all other species being found at low elevations along or near the eastern coast.

Conservation status. – Lijndenia darainensis is known from a single location and has an AOO of 4 km 2. The Binara forest, in spite of its protected-area status within the Station forestière à Usage multiple de Loky-Manambato (gazetted in 2005), is subject to anthropogenic pressures including removal of hardwood timber, slash-and burn-agriculture, and pasturage of zébu cattle ( RAKOTONDRAVONY, 2006). Lijndenia darainensis is thus provisionally assessed as “Vulnerable” [VU D2] according to the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Lijndenia darainensis has been previously confused with L. danguyana . The leaves of the two species are similar, but in L. darainensis the lateral nerves are very weak and situated 1-2 mm from the margins whilst in L. danguyana they are more clearly visible and situated c. 5 mm from the margins at the midpoint of the blade. The type locality of L. darainensis is also isolated by a distance of c. 450 km from the nearest known locality of L. danguyana (i.e. near lac Alaotra in Toamasina province).

[Photos: A, B: L. Gautier; C: L. Nikolov]

The blue flowers and apparently 1-nerved, cuneate-obovate leaves of L. darainensis also resemble those of L. roborea . These two species differ in stature ( L. darainensis a tree 20 m versus a shrub or tree 2-6 m in L. roborea ) as well as the texture of the leaves (thinly coriaceous with intramarginal nerves faintly visible versus thickly coriaceous with intramarginal nerves ± invisible). Moreover, L. darainensis inhabits montane forest in extreme northeastern Madagascar whilst L. roborea is found in littoral forest along the island’s east-central coast.

Figures

Fig. 4. – Living material. A. Lijndenia darainensis R.D. Stone, flowering branchlets; B. Lijndenia darainensis R.D. Stone, flowers; C. Lijndenia melastomoides (Naudin) Jacq.-Fél., flowers.

Fig. 3. – Geographic distribution of Lijndenia danguyana (H. Perrier) Jacq.- Fél. (circles), L. darainensis R.D. Stone (black star), L. melastomoides (Naudin) Jacq.-Fél. (squares), L. ramiflora Jacq.-Fél. (triangle), L. roborea (Naudin) Jacq.-Fél. (diamonds), and L. terminalis Jacq.-Fél. (white star), mapped on the bioclimatic zones of Madagascar (after CORNET, 1974; see SCHATZ, 2000).