Jongkind, C. C. H. & L. Gautier (2011). Combretum nusbaumeri Jongkind & L. Gaut. (Combretaceae), a new species from Madagascar. Candollea 66: 311–315. In English, English and French abstracts.
The new species Combretum nusbaumeri Jongkind & L. Gaut. (Combretaceae) that is endemic to north-eastern Madagascar is described and illustrated. It belongs in subgen. Cacoucia (Aubl.) Exell & Stace sect. Calopyxis (Tul.) Jongkind and is related to Combretum evisceratum (H. Perrier) Jongkind and Combretum macrocalyx (Tul.) Jongkind, two forest climbers that are also found in the same region. It differs quite markedly from them by the densely hairy receptacle and the style which is barely exserted.
Just over 15 years ago Jongkind (1995) started a revision of the genus Combretum (Combretaceae) from Madagascar. Since that time a number of new Combretum species have been found on the island and C. nusbaumeri Jongkind & L. Gaut., described in this article, is one of these (Fig. 1). With its long campanulate, 5-merous upper receptacle, the absence of petals and its wingless fruits, it belongs without doubt to Combretum subgen. Coucia (Aubl.) Exell & Stace sect. Calopyxis (Tul.) Jongkind. Only a part of the sect. Calopyxis was revised by Jongkind (1995), but the new species happens to belong to this part. Within the section Calopyxis there are only few species with all 10 stamens clearly exserted like those of the new species, and with a comparatively large inflated disk. With this inflated lower part of the upper receptacle, which includes the disk, Combretum nusbaumeri resembles C. evisceratum (H. Perrier) Jongkind (Fig. 2) and C. macrocalyx (Tul.) Jongkind (Perrier de la Bâthie, 1954: 19, Fig. IV, 7, 8 & 31, Fig. VII, 5–7), two forest species of wider distribution that are also found in north-eastern Madagascar, as is the new species (Fig. 3). However, the distinction of these three species is easy based on flowering or fruiting material (see Table 1). The new species does not have long exserted stamens like C. macrocalyx and the upper receptacle is not clearly inflated like in C. evisceratum, its whole flower is also much more hairy than in the other two species. The fruits of the new species differ in being completely wing- or ridge-less and also conspicuously hairy.
Fig. 1.
Combretum nusbaumeri Jongkind & L. Gaut., field photos of the plant from which the type was collected (Nusbaumer & Ranirison 1521). A, B. Inflorescence. C.. Fruits.
[Photos : L. Nusbaumer]
Fig. 2.
Combretum evisceratum (Tul.) Jongkind, flowers (Nusbaumer & Ranirison 1953).
[Photo : L. Nusbaumer]
The new species occurs in the Loky-Manambato (Daraina) area where vegetation consists is made up of ca. 12 forest blocks 800–6000 ha each, within a secondary grassland matrix that was deforested, presumably several centuries ago (Goodman & Wilmé, 2006). Evergreen humid forest occurs on the two highest hills (ca. 1100 and 1200 m) and various types of semi-deciduous to dry forest occur in forest blocks at lower elevations. The new species comes from the Antsaharaingy forest block which is located North of the area, with a maximum elevation of 126 m, and on sandy soils, opposed to the sandstone substratum of the other forest blocks. It harbours the driest forest type of the area with a low canopy (6 to 8 m high), the tallest trees reaching a maximum of 12 m (Gautier & al., 2006).
Fig. 3.
Distribution of Combretum macrocalyx (Tul.) Jongkind (black squares), C. evisceratum (H. Perrier) Jongkind (white triangle) and C. nusbaumerii Jongkind & L. Gaut. (white star), with shading representing elevation.
Combretum nusbaumeri Jongkind & L. Gaut., spec. nova
(Fig. 1)
Typus: Madagascar: Antsiranana (Diego Suarez), souspréfecture de Vohémar, commune rurale de Daraina, forêt d'Antsaharaingy (12°55′S 49°40′E), 85 m, 1.III.2005, Nusbaumer & Ranirison 1521 (holo-: WAG; iso-: G; TEF).
Frutex volubilis vel liana, Combretum eviscerati affinis sed receptaculo albo dense pubescenti campanulato apicem versus non constricto, stylo vix exserto et fructus subgloboso costato (non alato) dense pubescenti ita in sectione trans versali globoso (non stellato) notabilis.
Description. — Twining climber several meters long. Twigs pubescent. Leaves opposite; petiole 5–10 mm long, densely hairy; lamina elliptic, 5–20 cm × 3–8 cm, with 5–10 pairs of main lateral nerves, densely pilose on both sides, base cordate, apex acute to shortly acuminate. Inflorescence a terminal, fewflowered bracteate raceme. Bracts linear, ca 12 × 1.5 mm, cream-coloured to pale brown, hairy. Flowers borne in pairs at each raceme node, white except for the brownish anthers, sessile or almost so; lower receptacle ca 4 mm long, completely covered with a very dense indumentum of 1 mm long whitish hairs; upper receptacle ca 2 cm long, with an inflated lower part including the disk, and a long campanulate upper part with 5 broad triangular lobes on top, densely white hairy outside with ascending 1 mm long hairs, mostly glabrous on the inside except for a patch of dense hairs at the edge of the disk and a few hairs on the inside of the calyx lobes; stamens 2-seriate, glabrous, attached to the upper receptacle some distance above the disk, ca. 5 mm exserted in living plant but only ca 1 mm in dry specimen; anthers 1.5–2 mm long; style hairy on lower 2/3, barely exserted from the receptacle. Fruit subglobose, unwinged but with 5 ridges, almost sessile, ca 1.5–2 cm in diameter, densely tomentose with whitish hairs.
Habitat and distribution. — Forest on sandstone about 6–8 m high with some emergents reaching 10–12 m. Only known from the type locality. The species has been seen in two other places in the same forest while conducting vegetation surveys. The species has never been encountered in any of the vegetation surveys conducted in the other forests of the area.
Conservation status. — With only two collections known, an AOO of 9 km2 (calculation following Callmander & al., 2007) and only one subpopulation, situated within an «Aire protégée à statut temporaire», the species is assigned a preliminary status of «Critically Endangered» (CR B2ab(i, iii, iv)) (UICN, 2001).
Etymology. — The species is named in honour of Louis Nusbaumer, who enthusiastically performed field work at Loky-Manambato together with his colleague Patrick Ranirison. Through their numerous collections and hard work in the field they made a significant contribution to the better understanding of flora and vegetation in the northern part of the Madagascar.
Additional specimens examined. — MADAGASCAR: Antsiranana (Diego Suarez), sous-préfecture de Vohemar, commune rurale de Daraina, forêt d'Antsaharaingy, 70 m, Ranirison 719 (G, TEF, WAG).
Table 1.
Principal differences between Combretum nusbaumeri Jongkind & L. Gaut., C. evisceratum (H. Perrier) Jongkind and C. macrocalyx (Tul.) Jongkind.
Acknowledgements
The authors would like to express their thanks to Adelaïde Stork for translation of the Latin diagnosis, to L. Nusbaumer for the map, and to an anonymous reviewer for comments on the manuscript. LG thanks the ONG «Fanamby» for assistance in the field and funding of part of the research program «Flore et Végétation de la région Loky-Manabato (Daraina)», and the University of Antananarivo, Département de Biologie et Ecologie Végétales, especially Patrick Ranirison, Roger Edmond and Prof. Charlotte Rajeriarison for a fruitful collaboration on this research programme. Further financial support for this project was received from Conservation International, Fondation «Jean-Marcel Aubert», the University of Geneva and the Conservatoire et Jardin botaniques de la Ville de Genève.
