Grewia hispidissima Wahlert, Phillipson & Mabb., 2016

Wahlert, Gregory A., Phillipson, Peter B., Mabberley, David J. & Lowry Ii, Porter P., 2016, Grewia hispidissima Wahlert, Phillipson & Mabb., sp. nov. (Malvaceae, Grewioideae): a new species of restricted range from northwestern Madagascar, Adansonia 38 (1), pp. 117-121 : 118-121

Grewia hispidissima Wahlert, Phillipson & Mabb. , sp. nov.

( Fig. 1 )

Grewia hispidissima Wahlert, Phillipson & Mabb. , sp. nov. differs from all other Malagasy members of the genus by its large acuminate leaves that are up to 30 cm long and 11.5 cm wide, and by its mixed simple and stellate ferruginous trichomes that densely cover the stems, petioles, inflorescence axes, pedicels and sepals.

TYPUS. — Madagascar. Prov. Antsiranana, Sambirano, Vallée de la Beandrona à l’Est d’Ambanja, 13°40’58”S, 48°29’28”E, 50- 150 m, 29.X.1954, fl., Service Forestier (Capuron) 11397 (holo-, P [ P00375156 ]! ; iso-, G!, MO!, P [ P00375157 ]!, TAN).

PARATYPES. — Madagascar. Prov. Antsiranana, Reg. DIANA: Fiv. Ambanja, Fir. Ambodimanga-Ramena, Fkt. Antsahabe , south east of village of Mandrizavona, river Bepaka, close to junction with Ramena, 13°51’02”S, 48°47’54”E, 516 m, 12.XI.2001, bud, fl., Antilahimena et al. 785 ( G!, MO!, P!, TAN, TEF). — Ramena valley from Betaindambo to Maevatanana, Fkt. Antsahabe, Fir. Ambodimanga, Fiv. Ambanja , 13°52’01”S, 48°49’54”E, 500 m, 9.X.1998, bud, fl., Birkinshaw et al. 536 ( MO!, P!, TAN). — Ambilobe, Commune Rurale Beramanja , Chaîne Galoka , Mont Galoka , Fkt. Anketrabe-Belinta , Galoka Relevé 1, 13°34’55”S, 48°43’06”E, 680 m, 19.II.2005, imm. fr., Callmander et al. 341 ( G!, MO!, NEU!, TEF). — Besinkara, Ambalafary , 1 er marigot sur le chemin d’Ambodisakoana ( Andavakevany ), 14°04’S, 48°17’E, 300 m, 4.XI.1997, bud, fl., Derleth 161 ( G, K, MO!). — Besinkara, chemin d’Ambalafary au Bekolosy , avant le gué de l’Andavakeva, 14°04’S, 48°17’E, 450 m, 27.VIII.1997, bud, fl., Gautier et al. 3196 ( G, K, MO!, P). — East of Ankaramy , RS Manongarivo , Bekolosy , 14°02’S, 48°19’E, 800-1000 m, 7-12.XII.1992, bud, fl., Malcomber et al. 1952 ( G, K, MO!, P!, TAN, US). — Fiv. Ambanja, Fir. Ambodimanga-Ramena, Fkt. Antsahabe, Antsaharatsy , 13°48’35”S, 48°47’36”E, 600 m, 14.IV.2000, bud, Rabenantoandro et al. 182 ( G, MO!, P!, TAN). — RS Manongarivo , à l’est d’Ankaramibe, Bekolosy , 14°03’05”S, 48°17’07”E, 600-800 m, 5.XII.1993, bud, fl., Rakotomalala & Malcomber 35 ( G!, MO!, P!, TAN). — Ambilobe, Beramanja , Anketrabe , forêt de Kalabenono , Chaîne de Galoko , 9 km au SE d’Anketrabe, 13°38’30”S, 48°40’53”E, 976 m, 23.XI.2006, bud, fl., Razafitsalama & Torze 1091 ( MO!, P!, TAN). — Ambilobe, Commune Rurale Beramanja , Chaîne Galoka , Mont Galoka , Fkt. Anketrabe-Belinta , Galoka Relevé 1, 13°34’56”S, 48°43’06”E, 647 m, 19.II.2005, bud, Wohlhauser et al. SW-750 ( G!, MO!, NEU, P!, TEF).

HABITAT AND DISTRIBUTION. — The new species is known from three mountain ranges in the Sambirano biogeographic region, viz. Manongarivo, Tsaratanana, and Galoka, at elevations of 50-976 m. It has been recorded from primary humid forest and in savoka and other disturbed areas, including one collection (Birkinshaw et al. 536) from a cultivated field of cannabis ( Fig. 2 ).

PHENOLOGY. — Flowering material has been collected between August and December.

ETYMOLOGY AND VERNACULAR NAME. —The specific epithet “ hispidissima ” refers to the dense hispid indument covering most parts of the plant. The vernacular name ‘ valovembaka ’ in the Sakalava dialect was recorded on two collections (Derleth 161 and Gautier et al. 3196).

DESCRIPTION

Shrub or small tree up to 10 m tall, bark fibrous, young parts mostly with a hispid indument composed of long (c. 2 mm) golden to ferruginous simple but often tufted trichomes together with very short (<0.2 mm) simple or stellate gray or beige trichomes; stems square in cross-section, weakly fluted, densely villous, lacking visible lenticels; stipules 7-12 mm long, lanceolate to narrowly triangular, caducous, abaxial surface densely hispid with long simple trichomes only, adaxial surface glabrous. Leaves alternate; petioles 6-30 mm long, densely hispid; blades 9-30 × 4-11.5 cm, elliptic-oblong,sub-palmatinerved but appearing penninerved, with 7 to 11 pairs of secondary veins, the basal two subopposite and extending upwards ⅓–½ the length of the blade, midvein and secondary veins raised abaxially, sunken adaxially, tertiary venation scalariform, lacking domatia, abaxial surface hispid, adaxial surface sparsely to moderately hispid, the indument most dense along the midvein and secondary veins on both surfaces, base cuneate to obtuse, margins doubly or irregularly serrate, apex acute or acuminate, acumen 1.5-4 cm long. Inflorescence a terminal or leaf-opposed, 4- to 10-flowered umbellate cyme, peduncles 6-18 cm long, 0.7-1 mm in diam., densely hispid; pedicels 11-20 mm long, densely hispid, bracts narrowly triangular, lanceolate to linear, sometime deeply bifid, 1-2.2 mm long, caducous, densely hispid on both surfaces. Flowers bisexual, pentamerous. Sepals valvate, strongly reflexed at anthesis, 11- 18 × 2.5-4 mm, oblong, abaxial surface with an indument comprising a dense covering of minute stellate trichomes and conspicuously tufted long simple trichomes, adaxial surface glabrous, base truncate, margins entire, scarious, undulate, apex acute, yellow or green in vivo. Petals 6-9 × 1.6-2.2 mm, lanceolate, glabrous on both surfaces, base truncate, margins entire, apex subacute to acute, yellow in vivo; the basal abaxial portion of the petal bearing a cordiform nectariferous pad, 0.6-1.2 × 1.7-2.0 mm, the lateral and apical portions with a membranous scale extending 0.2-0.5 mm above the apex of the pad, the scale margin densely hirsute with simple pale beige trichomes (c. 1 mm long); androgynophore 1.1-2 mm long, slightly dilated toward the apex, weakly fluted in crosssection, glabrous but with 5 tufts of simple beige trichomes at the apex. Stamens 25 to 100, yellow in vivo, filaments 8-14 mm long, filiform; anthers 0.5-0.6 × 0.5-0.6 mm, subspherical. Ovary c. 1-2 × 1-2 mm, ovoid, 4-lobed, densely hirsute, the surface completely obscured by simple beige trichomes, locules 4, ovules 1 per locule, style 9-14 mm long, glabrous, stigma capitate, shallowly 5-lobed. Fruits, green in vivo when young, mature fruit unknown.

REMARKS

Grewia hispidissima Wahlert, Phillipson & Mabb. , sp. nov. is readily distinguished from all other Malagasy members of the genus by its very large, acuminate leaves and the dense hispid indument comprising long golden to ferruginous trichomes and short stellate trichomes on its stems, petioles, inflorescence axes, pedicels and sepals. Mature fruiting material is not known, and without it we are unable to assign this new species to an infrageneric group. Capuron evidently considered it to be closely related to two additional entities, as indicated by the fact that he annotated three Service Forestier collections in the Paris herbarium from Ankarana and Marotaolana in the dry north of Madagascar (SF 23130 [2 sheets], SF 23158 [1 sheet], and SF 23344 [1 sheet]) as “ Grewia hispidissima var. septentrionalis ” and Service Forestier 18918 [3 sheets] from near Ambanja in the sub-humid north-west as “ Grewia hispidissima var. parvifolia .” These unpublished infraspecific names were not mentioned under “ Grewia hispidissima ” in Capuron’s original manuscript. After careful examination of this material, we conclude that none of it is conspecific with the new species we here describe as G. hispidissima Wahlert, Phillipson & Mabb. , sp. nov., but rather differs by its much smaller and differently-shaped leaves and smaller flowers. Moreover, although the stems and leaves of these specimens are also hispid, the indument is not ferruginous as in G. hispidissima Wahlert, Phillipson & Mabb. , sp. nov. and the distribution of simple and stellate trichomes on various parts also differs. While the status of these two undescribed entities requires further clarification, they both appear to be morphologically similar to certain collections associated by Capuron with G. cuneifolia Juss. , differing mainly by their hispid indument, which is lacking in G. cuneifolia , a taxon characterized by a finer indument of stellate trichomes. The widespread G. cuneifolia species complex, in which Capuron was planning to recognize six forms, is clearly in need of taxonomic revision.

CONSERVATION STATUS

Grewia hispidissima Wahlert, Phillipson & Mabb. , sp. nov. has three known locations representing three subpopulations, two of which are situated at the edge of well-established protected areas (Manongarivo Special Reserve and Tsaratanana Strict Nature Reserve) and the third within a site (Galoko-Kalobinono) that has recently been accorded permanent protection within Madagascar’s enlarged protected area network. Based on the currently available data, the Extent of Occurrence (EOO) of the species is estimated to be 1108 km 2, a significant proportion of which is not under protection, and its estimated Area of Occupancy (AOO) is 80 km 2. Continuing decline can be projected both for the extent and quality of the available habitat due to ongoing land clearance for agriculture in areas that are not currently under protection and the significant negative impact on habitat at the margins of protected areas resulting from burning in adjacent open areas for grazing. Grewia hispidissima Wahlert, Phillipson & Mabb. , sp. nov. is therefore assigned a preliminary conservation status of Endangered [EN B1ab(i,ii,iii)+2ab(i,ii,iii)].

Figures

FIG. 1. — Grewia hispidissima Wahlert, Phillipson & Mabb., sp. nov.: A, flowering branch; B, flower; C, immature fruit. A-C, Service Forestier (Capuron) 11397 (holotype P[P00375156]). Drawn by Roger Lala Andriamiarisoa. Scale bars: 1 cm.

FIG. 2. — Geographic distribution of Grewia hispidissima Wahlert, Phillipson & Mabb., sp. nov. (ê) in northwestern Madagascar.