Grewia mabberleyana Phillipson, Wahlert & Lowry, 2015

Wahlert, Gregory A., Phillipson, Peter B. & Lowry Ii, Porter P., 2015, A new species of Grewia L. (Malvaceae, Grewioideae) from northeastern Madagascar, Candollea 70 (2), pp. 201-205 : 202-205

Grewia mabberleyana Phillipson, Wahlert & Lowry , spec. nova

( Fig. 1 ).

Typus: MADAGASCAR. Prov. Toamasina: Ambodiriana, RN de Betampona , [17°55’S 49°13’E], 28-29.XI.1962, buds & fl., Service Forestier 22132 (holo-: P [ P00246537 ]! ; iso-: BR, CAS, G [ G00341580 ]!, P [ P00722595 , P00722596 ]!, K, MO-2282215 !, NY, S, TEF [ TEF000879 ]!, WAG ).

Grewia mabberleyana Phillipson, Wahlert & Lowry is most similar morphologically to G. thouvenotii by the densely stellate indument present on the young stems, abaxial surfaces of the leaves, petioles, peduncles, and pedicels, and the adaxial surfaces of the sepals, and by the discolorous leaves. It differs by its much longer peduncles (13-20 mm in G. mabberleyana vs. 4-10 mm in G. thouvenotii ) and pedicels (11-15 mm vs. 3-5 mm), its larger sepals (5-12 mm vs. 3.5-4.5 mm), and its leaves drying light green (vs. brownish-gray).

Tree 10-25 m tall, trunk to 50 cm in diameter, evergreen, young stems densely covered with white-beige stellate trichomes, lenticels absent; stipules 1-2 mm long, narrowly triangular to linear, caducous, abaxial and adaxial surfaces densely stellate-pubescent. Petiole 5-10 mm long, densely stellate pubescent. Leaves alternate; blade 2.5-8 × 1-3.3 cm, oblanceolate to oblong-elliptic, discolorous, abaxial surface densely covered with stellate trichomes giving it a velvety appearance and feel, lacking domatia, adaxial surface sparsely to moderately stellate-pubescent, base cuneate, margins entire to shallowly serrulate, apex acute to rounded, rarely shortly acuminate; midvein, secondary and tertiary veins densely stellate pubescent on abaxial surface, sparsely to moderately so on adaxial surface; blade sub-palmatinerved but appearing penninerved, with 3 or 4 pairs of secondary veins, the basal two secondary veins subopposite and extending distally ca. ½ the length of the blade, midvein and secondary veins raised abaxially, not raised adaxially, tertiary venation scalariform. Inflorescence a terminal or subterminal umbellate cyme, 4- to 8-flowered, peduncle 13-20 mm long, 0.7-1 mm in diam., densely stellate-pubescent; pedicels 11-15 mm long, densely covered with stellate trichomes, pedicel bracts narrowly triangular to linear, 1-2.2 mm long, caducous, both surfaces densely stellate-pubescent. Flowers bisexual, pentamerous, rarely tetramerous, fragrant. Sepals valvate, erect in bud, reflexed at anthesis, 5-12 × 1-2.6 mm, narrowly oblong, yellow in vivo, abaxial surface densely covered with white-beige trichomes, adaxial surface glabrous except for a small basal tuft of white trichomes, base truncate, margins entire, apex acute. Petals 3-6.5 × 0.7-1.4 mm, narrowly oblong, yellow in vivo, glabrous on both surfaces, base truncate, margins entire, apex rounded; the basal adaxial portion of the petal bearing a papillose nectiferous pad 0.6-1 × 0.6-1.1 mm, lateral and apical portions of pad with a brown, membranous scale, margin of scale densely covered with white-beige trichomes and extending 0.6-1.2 mm above the apex of the pad; androgynophore 0.6-1.4 mm, glabrous. Stamens 30 to 60, yellow in vivo, filament 5-9 mm long, filiform; anther 0.3-0.5 × 0.3-0.5 mm. Ovary ca. 1 × 1 mm, completely covered with white-beige trichomes, style 6-9. 5 mm long, green in vivo, stigma often 5-lobed. Fruit incompletely known, drupaceous, 2- or 3- (or 4?)-lobed, ca. 0.75 × 0.75 cm, surface papillose, sparsely covered in minute stellate trichomes.

Etymology. – The new species is named in honor of Professor David J. Mabberley, who has worked extensively on the diversity and taxonomy of Grewia in Madagascar, and has co-authored published revisions for two of its subgenera.

Distribution and habitat. – Grewia mabberleyana grows in humid and subhumid forests of northeastern and eastern Madagascar, from sea level to 1700 m elevation ( Fig. 2 ). It is known from collections made in four protected areas: Anjanaharibe-Sud Special Reserve, Betampona Strict Nature Reserve and the Mananara-Nord and Masoala National Parks. It has also been collected just outside the Marotandrano Special Reserve, and probably also occurs within this protected area. By comparison, G. thouvenotii generally occurs further south, extending from Zahamena National Park and the forests around Moramanga, including in the Analamazaotra Special Reserve, to Ranomafana National Park more than 400 km to the south, where a single collection is known (for more details see the treatment in MADAGASCAR CATALOGUE, 2015).

Conservation status. – Five of the six known subpopulations of G. mabberleyana are located within protected areas (including two within Betampona Strict Nature Reserve) that recently have, however been subjected to illegal logging and pressures resulting from other human activities, in particular slash and burn agriculture. With an Extent of Occurrence of 23,655 km 2 and an Area of Occupancy of only 70 km 2, G. mabberleyana is therefore assigned a preliminary conservation status of “Near Threatened” [NT] following IUCN Red List Categories and Criteria ( IUCN, 2012).

Vernacular names and uses. – The following names have been recorded for G. mabberleyana on associated specimen labels: “afotrafotsy” (Réserves Naturelles 5897) and “hafotrankora” (Service Forestier 26231). As with many other species of Grewia in Madagascar, the fibrous bark is used to make cord (Service Forestier 26231).

Paratypi. – MADAGASCAR. Prov. Antsiranana: SW d’Andapa, Anjanaharibe-Sud PA, village de Mandritsarahely , 14°43’10’’S 49°27’12’’E, 1700 m, 14.II.1995, fr., Ravelonarivo & Rabesonina 664 ( MO, P, TAN) . Prov. Mahajanga: Mandritsara District , Antsiatsiaka village near Marotandrano , [16°18’11’’S 48°51’19’’E], 13.XI.1966, fl., Service Forestier 26231 ( BR, CAS, E, G, K, MO, NY, P, S, TEF, WAG) . Prov. Toamasina: Parc national de Mananara-Nord , près d’Antanambe , env. du camp, PK5, 3.XII.1989, imm. fr., Morat et al. 8610 ( P) ; RNI de Betampona , 17°54’46’’S 49°12’20’’E, 427 m, 20.XI.2001, fl, Rabehevitra et al. 15 ( G, MO, TEF) ; ibid. loc., 17°54’23’’S 49°12’16’’E, 392 m, 26.XI.1998, fl., Randrianaivo & Westerhaus 281 ( BR, G, MO, P, US, TAN) ; ibid. loc., [17º55’S 49°13’E], 19.XI.1953, fl., Réserves Naturelles 5897 ( MO, P, TEF) ; Masoala Peninsula, Ambanizana , “S Trail ” (S of Androka River), 15°38’S 49°59’E, 400 m, 29.X.1992, fl., Schatz et al. 3356 ( BR, G, K, MO, P, TAN, US, WAG) . Prov. unknown: Masoala , 500 m, 1912, fl., Perrier de la Bâthie 5587 ( G, P) .

Figures

Fig. 1. – Grewia mabberleyana Phillipson, Wahlert & Lowry. A. Flowering branch; B. Leaf, abaxial surface; C. Flower. [Service Forestier 22132, P] [Drawn by R. L. Andriamiarisoa]

Fig. 2. – Geographic distribution of Grewia mabberleyana Phillipson, Wahlert & Lowry (circles) mapped on the bioclimatic zones of Madagascar (after CORNET, 1974; see SCHATZ, 2000).