Grewia gautieri Wahlert & Nusb., 2014

Wahlert, Gregory A., Nusbaumer, Louis & Ranirison, Patrick, 2014, Grewia gautieri Wahlert & Nusb. (Malvaceae, Grewioideae): a new species from Madagascar, Candollea 69 (2), pp. 149-155 : 150-154

Grewia gautieri Wahlert & Nusb. , spec. nova ( Fig. 1-3 ).

Typus: MADAGASCAR. Prov. Antsiranana: sous-préfecture de Vohemar , Daraina , forêt d’Antsahabe , 13°12’50’’S 49°31’47’’E, 468 m, 25.I.2006, bud, fl., Nusbaumer & Ranirison 1983 (holo-: G [ G00090340 ]!; iso-: MO!, K!, P!, TEF, research herbarium of Daraina).

Grewia gautieri Wahlert & Nusb. is similar to G. brideliifolia Baill. by its 4-merous flowers, 3-flowered cymes, and fibrous, indehiscent, drupaceous fruits, but differs by its chartaceous leaves that dry green-brown to light brown (vs. coriaceous leaves that dry dark brown to black-brown in G. brideliifolia ), petals that lack, or only very rarely have, a nectariferous gland (vs. a well-developed nectariferous gland), and fruits that contain a single pyrene (vs. fruits that contain 4-8 pyrenes).

Shrub or small tree up to 9 m tall; young stems sparsely to moderately pubescent with white simple trichomes up to 0.6 mm long and minute stellate trichomes up to 0.8 mm long; young branches without leaves and covered with stipules. Stipules linear, 1.5-5.5 × 1-3 mm, persistent, brown in vivo, sparsely to moderately pubescent with simple trichomes like those of the stem, apex acute. Leaves alternate, chartaceous; petiole 0.5-2.5 mm long, sparsely to moderately pubescent; blade 1.6-5.8 × 0.7-2 cm, elliptic-lanceolate to ± rhombic, green-brown when dry, glabrous to sparsely pubescent with simple trichomes on both surfaces, sparsely to moderately pubescent on the primary and secondary veins on both surfaces, base cuneate to rounded, margin serrate to serrulate, apex acute to rounded; blade sub-palmatinerved but appearing penninerved, with 2-5 pairs of secondary veins, the basal two secondary veins subopposite and extending upwards ca. ½ the length of the blade, tertiary veins reticulate, midvein, secondary and tertiary veins slightly raised on both surfaces; domatia sometimes present in the axils of the midvein and secondary veins. Inflorescence an axillary umbellate 3-flowered cyme; peduncle 0.2-3.7 mm long, sparsely to moderately pubescent with simple trichomes; pedicels 4-8 mm long, sparsely to moderately pubescent with simple trichomes; pedicel bracts narrowly triangular-linear, 0.8-2 mm long, abaxial surface sparsely to moderately pubescent with simple trichomes, margin ciliolate, apex acute, recurved. Flowers 4-merous, very rarely 5-merous; calyx erect in bud, sepals valvate, strongly reflexed at anthesis, 3.8-5 × 0.6-1.8 mm, oblong to oblanceolate, often slightly constricted near the middle, abaxial surface sparsely to moderately pubescent with simple and stellate trichomes, densely stellate-pubescent along the margin, adaxial surface glabrous to sparsely pubescent with simple and stellate trichomes, margin entire, revolute, apex acute, creamy-white to light green in vivo, with a light red, rose or orange patch at the base of the adaxial surface; petals 3-4 × 0.3-1 mm, oblong to oblanceolate, glabrous to sparsely pubescent with simple and stellate trichomes abaxially and adaxially, sometimes moderately to densely pubescent towards the base on the adaxial surface, margin entire, apex bifid, white to cream in vivo, drying brown-orange, nectariferous gland absent or only very rarely present in a reduced or vestigial state on the lower adaxial surface; androgynophore 0.4-0.9 mm, glabrous, receptacle densely pubescent; stamens ca. 20 to 35, filament 1.5-3 mm long, laterally flattened, often fluted in cross section, glabrous, yellow-white in vivo, anther ellipsoid, 0.3- 0.4 × 0.2-0.3 mm, yellow to orange in vivo; ovary densely hirsute with whitish simple trichomes, style 2-3 mm long, stigma 4-lobed. Fruit a fibrous, indehiscent drupe containing a single pyrene, ± round to irregularly shaped, wrinkled, 5-7 mm long, 4-7 mm in diam., moderately pubescent with whitish simple trichomes, whitish-green to whitish-yellow in vivo, pyrene obovoid-discoid, 3.9-4.1 mm × 2.2-3.5 mm, 1.2-1.5 mm thick, beige-brown, foveolate.

Distribution. – The species is known primarily from Antsiranana Province in the Loky-Manambato region (Daraina), but also on the slopes of Montagne d’Ambre and Bezavona Massif near the southwest of Vohemar in the North of Madagascar. A single individual (Ratovoson & al. 642) is disjunctly distributed ca. 450 km to the south, near the NE portion of Alaotra Lake in Toamasina Province ( Fig. 4 ).

Habitat and ecology. – Grewia gautieri occurs in humid forests, semi-deciduous forests, and along streams or rivers in dry forests up to 1,100 m elevation. It grows on a variety of geological substrates, including metamorphic rocks, basalts, lake deposits, and sandstones. In the Loky-Manambato region, where a detailed vegetation study and floristic inventory was conducted ( GAUTIER & al., 2006; RANIRISON, 2010; NUSBAUMER, 2011), the species was found in forests with canopies reaching up to 14 m, with some emergent trees reaching up to 18 m. The species most frequently recorded together with Grewia gautieri are, in decreasing order: Dracaena xiphophylla Baker , Strychnos madagascariensis Poir. , Drypetes perrieri Leandri , Mallotus oppositifolius (Geiseler) Müll. Arg. , Pandanus analamerensis Huynh , and Diospyros olacinoides (H. Perrier) G. E. Schatz & Lowry.

Phenology. – Based on herbarium specimen label data, the species flowers from January to March and fruits from February to March.

Notes. – The new species described here is tentatively placed in Grewia subg. Burretia as circumscribed by CAPURON (1963). The subgenus is poorly delimited using just two characters (the shape of the stigma and the morphology of the fruit), yet we have included G. gautieri in the subgenus based mainly on its morphological similarity to G. brideliifolia . There are at least two other species in the subgenus that have 4-merous flowers (G. ambongoensis and G. microcyclea ), but much further study is needed to understand how this character state is distributed among other species of Grewia in Madagascar, if at all.

One of the most striking morphological features of G. gautieri is the complete lack of a nectiferous gland on the basal adaxial portion of the petal. Among all of the flowering material studied for the new species, only a single specimen from the forêt d’Antsahabe (Nusbaumer 1066) had a nectiferous gland, which was somewhat vestigial or reduced in size. The combination of characters for G. gautieri (i.e., absence of a gland, chartaceous leaves that dry green-brown, and fruits that contain a one single-seeded pyrene), should serve to readily delimit it from G. brideliifolia and other unnamed specimens from nearby littoral forests in Antsiranana Province (e.g., Ratovoson & al. 827; Rabehevitra & al. 929 and 4493; Rabenantoandro & al. 1082 and 1285). The specimen, Ratovoson & al. 642, from Toamasina Province, is far out of the range of the core area of distribution for the species, but it closely matches the other specimens from Antsiranana Province, including the lack of a nectiferous gland.

One herbarium specimen (Meyers 40) records that the leaves are eaten by a lemur, the Golden-crowned Sifaka (Propithecus tattersalli).

Vernacular name. – The common name “ sely ” was recorded from one herbarium specimen (Meyers 256); a name that has been applied to other species of Grewia in Madagascar.

Conservation status. – With an AOO of 180 km 2 and an EOO of 25675 km 2 and 67 occurrences known (including 15 herbarium specimens collected and 52 occurrences based on previous vegetation studies) among 13 subpopulations of which 12 occur in protected areas, G. gautieri is assigned a preliminary status of “Near Threatened” (NT) following the IUCN Red List Categories and Criteria ( IUCN, 2012, calculation following CALLMANDER & al., 2007; MOAT, 2007).

Etymology. – The new species is named in honor of Laurent Gautier (G) who initiated the Loky-Manambato botanical project. Gautier also provided LN and PR the opportunity to carry out research for their dissertation in the Daraina region and instilled in them his passion for the study and conservation of the Malagasy flora.

Paratypi. – MADAGASCAR. Prov. Antsiranana: Montagne d’Ambre, silva Montana procera , 1000 m, 20-21.XII.1967, fl., Bernardi 11969 ( G [ G00170781 ]!); Analamazava, part of Binara Range , SW of Daraina ( Vohemar ), 200-1180 m, 23.II.1990, y. fr., Meyers 40 ( MO, P!, TAN); ibid. loc., 23.I.1991, buds, Meyers 256 ( MO!, P!); Antsahalalina, part of Bobankora Range , 12 km E of Daraina, 13°14’S 49°46’E, 205-607 m, 15.III.1990, fr., Meyers & Boltz 67 ( MO, TAN); Daraina, forêt d’Antsahabe , 13°13’10”S 49°33’5”E, 855 m, 20.I.2004, buds, fl., Nusbaumer 1066 ( G [ G00006507 ]!, K!, MO!, P!, TEF, research herbarium of Daraina); Daraina, forêt d’Ankaramy , 13°17’15’’S 49°40’44’’E, 250 m, 23.II.2004, fr., Nusbaumer & Ranirison 1209 ( G [ G00028467 ]!, K!, MO!, P!, TEF, research herbarium of Daraina); Daraina, forêt d’Ampondrabe , 12°57’44’’S 49°41’13’’E, 450 m, 18.II.2005, fr., Nusbaumer & Ranirison 2133 ( G [ G00086433 ]!); ibid. loc., 12°56’59’’S 49°42’38’’E, 423 m, 20.II.2005, fr., Nusbaumer & Ranirison 2134 ( G [ G00070033 ]!); bord du Makys , vers 800 m, XI.1932, fl., Perrier de la Bâthie 18836 ( G, MO, P [ P00262016 , P00262017 ]!, TAN); Daraina, forêt d’Ambilondamba , 13°09’39’’S 49°38’47’’E, 390 m, 1.II.2004, imm. fr., Ranirison & al. 375 ( G [ G00028054 ]!, K!, MO!, P!, TEF, research herbarium of Daraina); Daraina, forêt d’Antsahabe , 400 m, 13°12’58’’S 49°31’36’’E, 24.I.2006, fl., Ranirison & Nusbaumer 1109 ( G [ G00090537 ]!, K!, MO!, P!, TEF, research herbarium of Daraina); Montagne d’Ambre, env. de la Station Forestière des Roussettes et du Petit Lac , [12°31’30’’S 49°10’20’’E], vers 1000- 1100 m, 18-20.XI.1958, fl., Service Forestier 20029 ( G, K, MO, NY, P [ P00262026 , P00263160 ]!, WAG); Massif de la Montagne d’Ambre , rive droite de la Rivière des Makis en aval de la grande cascade, [12°31’S 49°10’E], 18-20.XI.1958, fl., Service Forestier 20048 ( G, K, MO, P [ P00262027 , P00262028 , P00263159 ]!, WAG); Massif du Bezavona, entre la Fanambana et la Manambery , pentes inférieures de la rive droite de l’Andilana , [13°32’S 49°54’E], 20.III.1967, buds, Service Forestier 27542 ( G, K, MO, P [ P06641824 ]!). Prov. Toamasina: Amparafaravola, Vohimena-Ambodisakoana à 7 km de Vohimenakely, 17°20’05’’S 48°38’21’’E, 10.I.2002, fl., Ratovoson & al. 642 ( MO, P!, TAN).

Figures

Fig. 1. – Inflorescence of Grewia gautieri Wahlert & Nusb. [Ranirison & Nusbaumer 1109] [Photo: P. Ranirison]

Fig. 2. – Fruiting plant of Grewia gautieri Wahlert & Nusb. [Nusbaumer & Ranirison 1209] [Photo: L. Nusbaumer]

Fig. 3. – Grewia gautieri Wahlert & Nusb. A. Flowering branch; B. Flower; C. Leaf. [Service Forestier 20048, P] [Drawn by R. L. Andriamiarisoa]

Fig. 4. – Map showing the distribution of Grewia gautieri Wahlert & Nusb. in Madagascar (circles), plotted on the map of phytogeographical domains sensu HUMBERT (1955).