Hibiscus fanambanensis M. Pignal & Phillipson, 2010

Pignal, Marc & Phillipson, Peter B., 2010, A new species of Hibiscus (Malvaceae) from Madagascar, Phytotaxa 14, pp. 43-48 : 44-46

Hibiscus fanambanensis M. Pignal & Phillipson sp. nov ( Fig. 1 , Fig. 2 , A, D, G)

H. mandrarensis similis , sed a floris minoris, bracteis calyculi minoribus (0.2 x 1 mm), calice glabro, corolla lutea, staminibus imo androphoro insertis, stigmatibus clavatibus pubescentibusque, differt.

Type:— Madagascar; Antsiranana Province, SAVA Region: Forêt d'Analalava (sur gabbros), au sud de Fanambana (Vohémar) [13°36'47"S, 49°59'09"E], 15-5-1966. R. Capuron 24880- SF ( P!- holotype P00574843 ; TEF-isotype) .

Large shrub with yellow flowers (fide Capuron). Young stems terete, pale grey, corky. Leaves simple. Stipules linear, deciduous, 3 mm long x 0.2 mm wide. Petiole 5 mm long x 1 mm diam., corky, glabrous or bearing scattered squamiform trichomes. Blade elliptic to obovate, 30-40 mm long x 20-25 mm wide, drying grey-green (adaxial surface) and brown-green (abaxial surface), glabrous except for scattered fasciculate trichomes on the abaxial surface along the midrib; base rounded-cuneate; apex truncate, mucronate; margin entire or coarsely serrate, slightly sinuous and slightly revolute; venation camptodromous, 3-nerved in the basal half, very conspicuous on the abaxial surface, slightly less so on the adaxial surface; the 2-3 pairs of secondary veins in the upper half forming an angle of 50-60° with the midrib; tranversal veins, slightly curved; ultimate veinlets just visible; areoles barely visible on the adaxial surface, polygonal. Flowers solitary, sub-terminal, opening widely. Peduncle articulated, 13-30 mm long x 1 mm diam., glabrous or bearing scattered fasciculate trichomes. Involucral bracts ca. 10, free, triangular, ca. 1 mm long x 0.2 mm wide, bearing a few fasciculate trichomes. Calyx campanulate, 7-8 mm diam. x 3.5-5 mm high, glabrous outside, with white hirsute indument inside, with 5 inconspicuous veins ending in the calyx teeth; teeth triangular, minute (ca. 0.2 mm long). Petals 5, ca. 32 mm long x 20 mm wide, yellow (fide Capuron); apex rounded; base attenuated, somewhat clawed; veins ca. 10, whitish tomentose outside, glabrous except for long white hairs at the base inside. Staminal column 12 mm long x 0.4 mm diam., very narrowly funnel-shaped with minute marginal teeth at the summit (0.1-0.2 mm long), glabrous except at the base adjacent to the petals, shorter than the style, bearing stalked stamens only on its lower two-thirds. Stigmas clavate, pubescent. Fruit unknown.

Etymology:—Refers to the only known locality of the species—near Fanambana town and the Fanambana river in SAVA Region, Antsiranana Province (Diégo-Suarez).

Conservation status:— The new species is known only from the type collection which was collected in Analalava forest a few km south of the town of Fanambana. The forest is at an elevation of about 250 m a.s.l., and is some 10 x 5 km in extent. It appears to be relatively intact judging from satellite images, but is adjacent to the RN5 Vohemar to Sambava road, undoubtedly under considerable threat, and possibly already rather degraded, as is the case with many lowland forests along the east coast of Madagascar. Its conservation status cannot be determined on the basis of the single collection from more than 50 years ago and must be regarded as 'Data Deficient' (DD).

Discussion:— Hibiscus fanambanensis belongs to the section Azanza , and it is clearly distinct from any existing species of the group. It is most similar to H. mandrarensis Humbert ex Hochr. , which occurs at midelevation in the south-east of Madagascar — and H. mangindranensis Hochr. , which (like H. famambanensis ) occurs in north-east Madagascar, but only in high elevation forest. Hibiscus fanambanensis differs clearly from these arborescent species by its shrubby habit (fide Capuron), different leaf venation and the following floral characters: the length and number of the epicalyx teeth; the indument of the calyx and the size of its teeth; perianth colour; the insertion of the stamens on the staminal column, the relative length of the column and the presence of apical teeth; and the indument of the stigmas. The differences between the three species in terms of these characters are summarized in Table 1 and illustrated in Figure 2 .

Figures

FIGURE 1. H. fanambanensis. General habit. R. Capuron 24880-SF (P00574843).

FIGURE 2. Comparison between H. fanambanensis (left) and H. mandrarensis (centre), H. mangindranensis (right). A, B, C. Leaf (scale-bar 1 cm). D, E, F, Flower, with staminal column and style details (scale-bar 1 cm), G, H, I, Calyx (scale-bar 0.5 cm). A, D. G., H. fanambanensis, R. Capuron 24880-SF, P00574843; B, E, H, H. mandrarensis, H. Humbert 13906, P030983, C, F, J, H. mangindranensis, H. Humbert & R. Capuron 24910, P030987.