Grewia manomboensis, Randrianasolo & Lowry Ii & Schatz & Phillipson & Wahlert, 2013

Randrianasolo, Armand, Lowry Ii, Porter P., Schatz, George E., Phillipson, Peter B. & Wahlert, Gregory A., 2013, The lianescent species of Grewia L. (Malvaceae s. l., formerly Tiliaceae) in Madagascar, Adansonia (3) 35 (1), pp. 73-85 : 76-78

1. Grewia manomboensis

G.E. Schatz, Randrian. & Lowry, sp. nov. ( Fig. 1 )

Haec species inter congeneros madagascarienses quoad habitum lianescentem Grewiae foliis venatione aspectu penninervis , inflorescentibus quatuor floribus pedunculo et pedicellis gracilissimis distinguitur.

TYPUS. — Madagascar. Prov. Fianarantsoa, Région Atsimo- Antsinana, Fivondronana Farafangana , Fokontany Manombo , Réserve Spéciale de Manombo , forêt dense humide de basse altitude sur latérite, 23°00’47”S, 47°43’34”E, 30 m, 14.XI.2001, fl., Rabenantoandro, McPherson & Gervais 779 (holo-, MO!; iso- P!, TAN!, TEF!).

PARATYPES. — Madagascar. Prov. Fianarantsoa, forêt littorale sur latérite à Iabomary , 40 km au SW de Farafangana, Mananivo, 23°03’34”S, 47°40’23”E, 0-50 m, 6.II.2001, Rabenantoandro et al. 413 ( MO, P, TEF) . — Région Atsimo-Antsinanana, Fivondronana Farafangana, Réserve Spéciale de Manombo , parcelle 1, forêt d’Anaviavy , forêt dense humide de basse altitude sur latérite, 23°00’39”S, 47°44’08”E, 12 m, 16.IX.2005, y.fr., Rakotonirina et al.301 ( MO, TAN) . — Reste de forêt sur latérite de basalte au S de Farafangana (route de Mahabo) au PK 13-17, [22°55’S, 47°47’E], 11.X.1964, fl., Service Forestier (Capuron) 23583 ( P) . DESCRIPTION

Lianas, stems brown, densely covered with beige stellate trichomes,eventually wearing off to reveal circular to elliptic lenticels. Stipules narrowly triangular to needle-like, densely covered with both simple and stellate trichomes. Leaves alternate, subcoriaceous, 1.5-5.2 × 0.9-2.2 cm, elliptic to ovate, adaxially initially with very scattered stellate trichomes varying in the number of arms from 2 to 6 and the length of arms from 0.01-0.5 mm, glabrescent, abaxially initially with very scattered trichomes along the midvein, secondary and tertiary veins, varying in the number of arms from 2 to 6 and the length of arms from 0.01-0.5 mm, glabrescent, finely verrucose,base acute to obtuse, margins serrate, each tooth terminating with a single simple trichome, apex acute to acuminate, blade sub-palmatinerved but appearing penninerved, craspedodromous, with 6 or 7 pairs of secondary veins, the basal two secondary veins subopposite and extending upwards c. ¼ the length of the blade at a slightly steeper angle (50-55°) than the remaining secondaries (35-40°), midvein slightly raised abaxially,raised adaxially, secondary and tertiary venation slightly raised abaxially, lacking domatia, flat adaxially, not evident. Petiole 2.5-4 mm, den- sely covered with both simple and stellate trichomes bearing 2 to 4 arms. Inflorescences pseudoterminal, umbellate, 2- to usually 4-flowered, peduncle slender, 5-6 mm long, to 10 mm in young fruit, 0.2 mm in diam., covered with stellate trichomes. Flowers bisexual, pentamerous, pedicel very slender, 10-12 mm long, to 15 mm in young fruit, 0.2-0.3 mm in diam., with sparse to moderately dense stellate trichomes, the epidermis visible, bearing caducous bracts 1-2 mm long at base; sepals valvate, erect in bud, strongly reflexed at anthesis, 8-10 × 1.3-3 mm, narrowly oblong, abaxially densely covered with whitish grey stellate trichomes, adaxially glabrous except with a tuft of trichomes at the base, yellow in vivo; petals 4-5 × 0.7-1 mm, narrowly oblong, densely covered with stellate trichomes on both surfaces, yellow in vivo, the basal 1 mm slightly broader and glandular, the gland densely ringed by tufts of beige simple and stellate trichomes, adaxially the pad of the gland densely papillose,androgynophore 0.7 mm, glabrous, receptacle shallowly 5-lobed, densely covered with simple and stellate trichomes; stamens 20 to 30 in 5 groups, filament 8 mm long, filiform, anther 0.3 mm in diam; ovary densely covered with whitish beige simple trichomes, style 9 mm long, stigma shallowly 5-lobed, papillose.Young fruit drupaceous, depressed globose, 5 mm tall, 6-7 mm in diam., glabrescent.

REMARKS

Grewia manomboensis sp. nov. is restricted to the Réserve Spéciale de Manombo and two nearby sites ( Fig. 2 ). It can be easily distinguished from the other lianescent members of the genus in Madagascar by its small leaves and usually 4-flowered umbellate inflorescences borne on very slender peduncles, with the flowers borne on very slender pedicels 0.2- 0.3 mm in diam. whose epidermis is only partially obscured by stellate pubescence.

CONSERVATION STATUS

Grewia manomboensis sp. nov. is known only from four collections, two from within theRéserve Spéciale de Manombo, one from a forest remnant c. 6 km to the north, and one from the forested area S of Parcelle 1 of the reserve. With an EOO of 77 km 2 and an AOO of 54 km 2, at no more than five locations, and given that the subpopulation in Parcelle 1 of the Manombo Reserve, on basaltic laterite, has suffered significant degradation during the last several decades, coupled with the fact that the unprotected subpopulations situated outside Manombo have/will undergo decline, and with a projected reduction of greater than 50% in the overall population in the next three generations (c. 45 years), the species is assigned a provisional conservation status of Endangered: EN A3c; B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v).

Figures

FIG. 1. — Grewia manomboensis G.E. Schatz, Randrian. & Lowry, sp. nov.:A, flowering branch; B, flower at anthesis; C, sepal (adaxial surface);D, sepal (abaxial surface);E, petal (adaxial surface with basal gland);F, petal (abaxial surface);G, detail of gynoecium;H, detail of leaf with venation. A-H, Rabenantoandro, McPherson & Gervais 779 (holotype, MO). Scale bars: A, 2 cm; B, 5 mm; C, D, E, 2 mm; F, 5 mm; G, 2 cm. Illustration by Barbara Alongi.

FIG. 2. — Distribution of new lianescent species of Grewia L., mapped on the bioclimatic zones of Madagascar (after Cornet 1974; see Schatz 2000): G. manomboensis G.E. Schatz, Randrian. & Lowry, sp. nov.; (☆), G. rufostellata Randrian., Lowry & G.E. Schatz, sp. nov. (N) and G. rabehevitrae Randrian., Lowry & G.E. Schatz, sp. nov. (p).