Hibiscus ankeranensis M. Hanes & G. E. Schatz 2020, sp. nov.

Hibiscus ankeranensis M. Hanes & G.E. Schatz, sp. nov. (Fig. 3B, 4B).

Holotypus: MADAGASCAR. Reg. Atsinanana [Prov. Toamasina]: Dist. Brickaville, Com. Maroseranana, Fkt. Ambodilendemy, Andrangato river, Ankerana, 18°26'52"S 48°46'28"E, 346 m, 13.III.2011, fl., Antilahimena 7544 (MO-2652132!; iso-: P [P06774026]!, TAN).

Hibiscus ankeranensis M. Hanes & G.E. Schatz differs from H. calyculatus (Hochr.) M. Hanes, G.E. Schatz & Callm. by its epicalyces, 5 non-symmetrical, succulent in vivo lobes (vs. 4 small, reflexed lobes), calyx color, green (vs. red), and its nonreflexed petals.

Tree c. 6 m tall, 12 cm dbh; twigs moderately densely covered with light, golden, semi-erect, simple, fascicled and stellate trichomes. Leaves 3.5– 9.8 × 1.9 –3.9 cm, elliptic to narrowly obovate, the base acute to obtuse, apex acuminate, the acumen to 1.2 cm, sometimes folded to one side, the tip rounded, glabrous and verruculose above, very sparsely covered with golden, stellate trichomes below, venation weakly brochidodromous with 7–10 secondary veins per side, with occasional intersecondary veins, midvein raised above and below, secondary veins slightly raised above and below, tertiary venation finely reticulate, slightly raised above and below; petiole 3–5 mm, 0.7–1 mm in diam., moderately densely covered with semi-appressed, curly light golden trichomes. Flowers solitary, axillary, pendent; pedicels 7–15 mm long, 0.2–0.7 mm in diam., densely covered with golden erect, simple and fasciculate trichomes; epicalyx with 5 free lobes, appearing somewhat succulent in vivo, the lobes 9 × 5 – 7 mm, ovate, the apex acute, sparsely covered with golden stellate trichomes on the outside, glabrous very sparsely covered with golden simple and stellate trichomes inside; calyx tubular with 4(–5?) lobes, fused for 5–7 mm, the lobes 2.5 × 2.5 mm, triangular, the apex triangular, moderately densely covered with golden stellate trichomes outside and inside; petals 5, 24 × 13 mm, obovate, the apex rounded to emarginate, red, sparsely covered with very light golden stellate trichomes outside, glabrous inside with evident venation; staminal column 20 mm long, 0.8 mm in diam., pinkish red, glabrous with very scattered minute trichomes; stamens 30–40(–50), filaments 8–10 mm, red, anthers 0.8 × 0.4 mm; styles 5, 8 mm, red, moderately densely covered with white trichomes, stigma c. 0.7 mm in diam., urceolate. Fruit unknown.

Distribution and ecology. – Hibiscus ankeranensis is known only from a single collection near the Andrangato river at Ankerana in the eastern coast of Madagascar at c. 350 m in elevation in lowland moist evergreen forests (Fig. 2).

[A: Ratovoson 2092; B: Antilahimena 7544; C: Razafitsalama 1409] [Photos: A: F. Ratovoson; B: P. Antilahimena; C: C. Birkinshaw]

Conservation status. – Hibiscus ankeranensis is known only from a single collection from the newly designated Corridor Ankeniheny-Zahamena protected area. We lack information on population size but lowland moist evergreen forests (below 800 m) are fragmented and heavily deforested in the region (GAUTIER, 2018). Recent satellite imagery from Google earth [https://www.google.com/intl/en/earth] suggests that the collection site and the surrounding area is deforested or disturbed. Hibiscus ankeranensis is therefore assessed as “Critically Endangered” [CR B2ab(iii)] using IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – Hibiscus ankeranensis is similar to H. calyculatus in corolla color but differs by its epicalyces with 5 lobes, 9 mm long (vs. 4(–5) lobes, reflexed, 3–4 mm long), calyx with 4(–5) teeth, green, succulent in vivo (vs. 5 teeth, red, inflated) and petals not reflexed (vs. reflexed).