Buxus cipolinica Lowry & G.E.Schatz, sp. nov.

(Fig. 1)

Haec species a Buxo humbertii foliis late obovatis 1.5-1.9- plo longioribus quam latioribus atque floris feminei sepalis late ovatis apice rotundatis differt.

TYPUS. — Madagascar. Prov. Fianarantsoa, 8 km S of Ambatofinandrahana, Mahavanyo, Analalehibe, disturbed thicket on marble, 20°37’44.7”S, 46°50’36.7”E, 1362 m, 27.XI.2004, ♂ and ♀ fl., fr ., C. Birkinshaw, A. Lehavana & Jean-Ba 1399 (holo-, MO!; iso-, G!, K!, P!, PRE!, TEF!, WAG!).

PARATYPE. — Madagascar. Prov. Fianarantsoa, rocailles à mi-chemin environ entre Ambatofinandrahana et Fenoarivo, 20°33’S, 46°48’E, 3.XII.1964, ster., Service Forestier 23903bis (TEF!) .

DESCRIPTION

Shrubs to 1.5 m, young stems 1 mm diam., with minute, erect trichomes, internodes 6-7 mm. Leaves sessile, very stiff and thick coriaceous, pale green in dry material, shiny, 1.1-1.7 × 0.6-1.1 cm, broadly obovate, broader above the middle, adaxially concave, apex rounded, minutely emarginate, margin slightly thickened, lighter in color, base attenuate, with minute, erect trichomes, midrib lighter that blade, slightly raised above and below, secondary venation visible above, more obscure below. Flowers sessile, axillary; male flowers solitary or (2-)3 per axil, borne at nodes well below branch ends, subtended by 2-4, slightly keeled, minute bracts; sepals 4, 0.6-1 × 1-1.2 mm, broadly ovate, apex rounded; anthers 4, sessile, 1.8-2 × 0.8 mm; female flowers solitary, borne at nodes closer to branch ends, subtended by 12-16 slightly keeled bracts, margin hyaline, the upper ones c. 1 mm long, the lower ones progressively smaller; sepals 4, 2 × 2-2.2 mm, broadly ovate, slightly keeled, apex rounded to obtuse, with a hyaline margin, styles 3, 2 mm long at anthesis, apex slightly recurved, stigma borne along inside of upper 2/3. Immature fruits 5.5 × 5 mm, broadly ellipsoid, stylar remnants 2 mm; developing seeds c. 5.5-4 × 1.5 mm.

REMARKS

Buxus cipolinica most closely resembles B. humbertii G.E.Schatz & Lowry, and material would be identified as that species using the key provided by Schatz & Lowry (2002). Our new species differs, however, in having broadly obovate leaves (vs. oblanceolate to obovate in B. humbertii) that are only 1.5-1.9 times as long as wide (vs. 2-3 times as long), and female flowers with broadly ovate (vs. triangular) sepals with a rounded (vs. acute to obtuse) apex. Buxus cipolinica is restricted to a small area with localized marble substrate S of Ambatofinandrahana in central Madagascar, whereas B. humbertii is probably associated with siliceous soils on gneiss, and reaches its northern limit in the Menarahaka River valley E of Ihosy (Schatz & Lowry 2002), some 200 km to the south.

The specialized marble (“cipolin”) substrates in the Ambatofinandrahana region to the east of the Itremo massif are highly restricted (see map 2 in Du Puy & Moat 1998). They are home to a number of locally endemic species, including Ormocarpopsis itremoensis Du Puy & Labat (Fabaceae), which is known only from precisely the same site as Buxus cipolinica (Du Puy et al. 2001) . Only a few fragments remain of the area’s original vegetation on marble (Du Puy & Moat 1996, 1998), and they are highly threatened by human-set fires as well as localized mining activities. It therefore seems unlikely, although not impossible, that additional populations of B. cipolinica occur elsewhere in the area.

Another distinctive member of the genus, Buxus calcarea G.E.Schatz & Lowry, is also found on calcareous substrates, but is restricted to semiarid deciduous thicket on tertiary limestone in Southern Madagascar (Schatz & Lowry 2002). Buxus itremoensis G.E.Schatz & Lowry is endemic to the Itremo massif just 25 km to the west of the site where B. cipolinica was collected, but it differs strikingly in being a rheophyte and is found only on substrates derived from quartzite.

CONSERVATION STATUS

Application of the IUCN (2001) threat criteria suggests that Buxus cipolinica should be assigned a status of Critically Endangered(CR B1ab(iii)2ab(iii)) based on an Extent of Occurrence <100 km 2, an Area of Occupancy <10 km 2, and a single known subpopulation at an unprotected site that faces continuing habitat decline from fires and mining.