Eremolaena darainensis Nusb. & Lowry, 2014

Lowry II, Porter P., Nusbaumer, Louis, Randrianasolo, Armand, Schatz, George E. & Hong-Wa, Cynthia, 2014, Endemic Families of Madagascar. XIII. New, restricted range species of Eremolaena Baill. and Schizolaena Thouars (Sarcolaenaceae), Candollea 69 (2), pp. 183-193 : 184-188

Eremolaena darainensis Nusb. & Lowry , spec. nova ( Fig. 1 , 2 A-D).

Typus: MADAGASCAR. Prov. Antsiranana: Région SAVA, sous-préfecture de Vohemar , commune rurale de Daraina , forêt de Bekaraoka , partie N, 13°07’06”S 49°42’34”E, 420 m, 17.I.2005, fl., Nusbaumer & Ranirison LN 1420 (holo-: G [ G00019278 ]!; iso-: K!, MO!, P [P00722548]!, TEF!).

Eremolaena darainensis Nusb. & Lowry differs from E. humblotiana Baill. by its smaller leaves, its flowers born singly (vs. in pairs) and its shorter sepals, and from E. rotundifolia (F. Gérard) Danguy by its stellate-lanate indument adjacent to the primary vein on the abaxial surface of the leaf (vs. absent), its smaller and less dense strigose-stellate indument on the sepals, and its presence in semi-deciduous forest on granite (vs. littoral forest on sand)

Small trees 8-12 m, 10-20 cm DBH, branched. Branches gray brown to reddish, glabrescent, with grayish lenticels, bark smooth; twigs of current year flattened, reddish-brown pubescent with gray to whitish stellate-strigose scattered trichomes. Leaves ovate to obovate, green, slightly discolorous, whitish on abaxial surface (brown when dry), chartaceous, 30-55 × 25-43 mm, 1-1.4(-1.7) times as long as wide, with erect white stellate indument 0.4-0.8(-1.1) mm long on abaxial surface adjacent to the primary vein, glabrous elsewhere, base subcordate to attenuate, margin flat in dry material, irregularly and weakly undulate when fresh, apex emarginate (rarely almost round), venation brochidodromous, with (5 or) 6 to 8 pairs of alternate to subopposite secondary veins, primary and secondary veins raised below, secondary and tertiary venation dark green, brown to purplish black in dry material, with sparse stellate-strigose indument on the venation of both surfaces and along the margin; petiole 8-17 mm long, with gray to whitish stellate-strigose indument, adaxially canaliculate; stipules triangular, 1.5-3 × 1-2 mm, canaliculate, brown, with white stellate-strigose indument, caducous. Flowers solitary, erect; pedicel green, brown-blackish when dry, 4-14(-16) mm long, with sparse to dense gray to whitish stellate-strigose indument, especially toward the apex; bracts foliose, 2-4(-5) × 1-2 mm, triangular, then 1.5 × 1 mm, covered with both dense white stellate-strigose and reddish-brown indument, caducous; flower subtended by a 3-lobed collar, the lobes 1.2 × 1.5 mm, with dense whitish stellate-strigose indument, giving it a whitish cast in fresh material; sepals 5, green, blackish when dry, entire, unequal, the 2 external ones smaller, triangular to deltoid, coriaceous, 1.5-3 × 1-2 mm, green, slightly purplish when fresh, the 3 internal ones imbricate, usually clockwise but sometimes counter-clockwise, ovate, asymmetrical, 9-14 × 6- 9 mm, glabrous, coriaceous or membranaceous where overlapped by an adjacent sepal, with gray to whitish stellatestrigose indument (trichomes to 0.25-0.35 mm diam.) where overlapping an adjacent sepal, trichomes of the overlapping part less dense at anthesis on the left side than on the right side, such that the foliaceous part (blackish in dry material) is visible; petals 5, obovate, white, equal, usually overlapping counter-clockwise, sometimes clockwise, always in the opposite direction from the sepals, convoluted, sub-irregular, 19- 22 × 8-10 mm, glabrous on both surfaces, apex rounded; extrastaminal disc cupuliform, 1 mm high, with an irregular margin; stamens ca. 90 to 110, filaments slender, white, 4-8 mm long, glabrous, anthers brown, 1-2 × 1 mm, introrse, anther sacs often oblique; pollen pale yellow; ovary spherical to shortly conical, with dense, cream to yellowish stellatestrigose indument (glabrous at the apex), 3-locular; style cylindrical, erect, pale yellow, 5-6 mm long, glabrous; stigma pale yellow, 3-lobed, 2 mm long, crateriform, margin distinctly undulate. Fruit unknown.

Distribution and ecology. – Eremolaena darainensis is restricted to the Bekaraoka and Ampondrabe forests in the Loky-Manambato (Daraina) region in north-eastern Madagascar ( Fig. 3 ). Among the more than 54,000 individual plants documented during recent floristic inventory work and vegetation studies conducted in this area, only 39 were found of E. darainensis USBAUMER & al., 2011), including just two fertile trees. Eremolaena darainensis is the northernmost member of the genus, separated by nearly 250 km from the closest known locality of E. rotundifolia (F. Gérard) Danguy just north of Cap Est, and almost 350 km from the most northern population of E. humblotiana Baill. Eremolaena darainensis is only known from flowering material gathered in January and February; no fruiting collections have yet been made. It grows in semi-deciduous (transitional) forest with a dense canopy reaching to 7- 12 m and a dense under-storey of shrubs. Our new species occurs at 250-550 m elevation and is usually found on fairly steep (20- 40°) slopes in fine soil on rocky outcrops. The most abundant co-occurring species include, in decreasing order, Euphorbia geroldii Rauh (Euphorbiaceae) , Asteropeia amblyocarpa Tul. (Asteropeiaceae) , Cleistanthus suarezensis Leandri (Phyllanthaceae) , and Rinorea angustifolia (Thouars) Baill. (Violaceae) .

Conservation status. – Eremolaena darainensis is currently known form five subpopulations, all of which are encompassed within the Loky-Manambato forest, which has been accorded temporary protection by the Malagasy government as a “Station Forestière à usages Multiples” (SFUM, Multiple Use Forestry Station), which falls short of full protection, indicating that some continuing decline of the quality of the habitat can be projected. Therefore, with an Extent of Occurrence (EOO) of 81 km 2, an Area of Occupancy (AOO) of 54 km 2, and five locations (calculated following CALLMANDER & al., 2007), as well as estimated number of mature individuals (based on extrapolation of the inventory data) of less than 2,500, with none of the five subpopulations estimated to contain more than 250 mature individuals, E. darainensis can be assigned a risk of extinction of “Endangered” [EN B1ab(iii)+ 2ab(iii); C2a(i)] following the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Using the key to species of Eremolaena provided by LOWRY & al. (2000), material of this new species would be identified as E. rotundifolia . It can, however, be distinguished from the two other members of the genus by several foliar and floral features, as well as differences in substrate preferences and geographic distribution ( Fig. 3 ). In order to facilitate identification of material of Eremolaena , the following updated key is provided.

Key to the species of Eremolaena Baill.

1. Leaves subcoriaceous, largest blades at least 9 cm long, secondary and tertiary venation distinctly raised on abaxial surface; sepals 15-19 mm long at anthesis; flowers borne in pairs, subtended by 5 small, scale-like involucral lobes; humid and subhumid forest on laterite, Betampona RNI and the area E of Zahamena NP, S to near Vatomandry ................................................................ E. humblotiana

1a. Leaves chartaceous, largest blade not exceeding 5(-6) cm long, secondary and tertiary venation weakly raised on abaxial surface; sepals 9-14 mm long at anthesis; flowers borne singly, subtended by a very small, 3-lobed collar .... 2

2. Abaxial surface of leaves with erect stellate white trichomes 0.4-0.6(-1.1) mm long borne along the midvein, apex emarginate (rarely sub-rounded), base subcordate to attenuate; sepals with stellate-strigose trichomes to 0.25-0.35 mm in diam., abaxial portion overlapped by adjacent sepal with scattered stellate-strigose trichomes revealing the foliaceous surface (blackish in dry material); semi-deciduous forest on ridge crests, granite, Loky-Manambato (Daraina) region ........................................................ E. darainensis

2a. Abaxial surface of leaves without white stellate trichomes along the midvein, apex usually rounded (rarely sub-emarginate), base attenuate; sepals with stellate-strigose trichomes to 0.35-0.5 mm in diam., abaxial portion overlapped by adjacent sepal totally covered with stellate-strigose indument at anthesis, obscuring the surface; littoral forest on sand, Masoala PN to Ft. Dauphin area....... E rotundifolia

Paratypes. – MADAGASCAR. Prov. Antsiranana: Région Sava, sous-préfecture de Vohemar , commune rurale de Daraina , forêt d’Ampondrabe , 12°57’07’’S 49°41’36’’E, 450 m, fl., 17.II.2005, Ranirison & Nusbaumer 936 ( G [ G00019280 ]!, K!, MO!, P [ P00722550 ]!, TEF!).

Figures

Fig. 1. – Eremolaena darainensis Nusb. & Lowry. A. Branch with buds and nearly open flowers; B. Detail of adaxial surface of leaf; C. Bud with pedicel; D. Branch with buds; E. Detail of abaxial surface of leaf; F. Detail of adaxial surface of leaf. [A-C: Ranirison & Nusbaumer PR 936; D-F: Nusbaumer & Ranirison LN 1420] [Drawing: R. L. Andriamiarisoa]

Fig. 2. – Photographs of Eremolaena darainensis Nusb. & Lowry (A-D) and Schizolaena charlotteae Lowry & G. E. Schatz (E). A. Flower, from above (petals fallen); B. Detail of midvein on abaxial leaf surface showing long white stellate trichomes near the margin and small stellate-strigose indument on nerves; C. Flower, from side (2 petals remaining); D. Detail of abaxial surface of a sepal, with stellate-strigose indument on the overlapping part less dense on the left side than on the right side; E. Flower and buds with young involucres. [A-D: Nusbaumer & Ranirison LN 1420; E. RandriataFika & al. 653] [Photos: A-D: L. Nusbaumer; E: P. Lowry].

Fig. 3. – Geographic distribution of Eremolaena darainensis Nusb. & Lowry (stars), Schizolaena charlotteae Lowry & G. E. Schatz (circles) and Schizolaena parvipetala Randrian. & Hong-Wa (squares), mapped on the bioclimatic zones of Madagascar (after CORNET, 1974; see SCHATZ, 2000).