Thursday, December 17, 2020

[Botany • 2020] Hibiscus hareyae (sect. Lilibiscus; Malvaceae) • Threatened in Coastal Thicket at Lindi, Tanzania

Hibiscus hareyae L.A.J.Thomson & Cheek
in Thomson & Cheek, 2020. 

The spectacular new species with horticultural potential described in this paper, Hibiscus hareyae L.A.J.Thomson & Cheek, was identified during an assessment of online digitised botanical specimens of H. schizopetalus (Dyer) Hook.f. as part of a review of species in Hibiscus sect. Lilibiscus Hochr. A short updated description and delimitation of the horticulturally important sect. Lilibiscus is presented. Flowering and fruiting specimens of Hibiscus hareyae are readily distinguished from H. schizopetalus by their short (0.4 – 2 (– 4.5) cm long, non-articulated peduncle-pedicels vs (6 –) 8 – 11 (– 14) cm long, articulated peduncle-pedicels, and larger, broader epicalyx bracts (1.5 – 4 × 1 – 1.2 mm vs 0.6 – 1.5 × 0.1 – 0.3 (– 0.5) mm), the epicalyx forming a shallow cup 0.5 – 1 × 2 – 3 mm vs bracts appearing free. The absence of an articulation of the peduncle-pedicel of H. hareyae is unique within sect. Lilibiscus. The species is also well-marked from H. schizopetalus by other morphological differences in corolla and foliage, and in ecology and geography. Hibiscus hareyae has a restricted natural distribution as an element in deciduous coastal thicket, usually on coral rag formations, sometimes in or near mangrove, in Lindi Province, southern Tanzania. It ranges from the Indian Ocean coast to as much as 20 km inland, from about 8.5oS to 10oS (c. 140 × 20 km) and is assessed as Vulnerable (VU B2ab(iii)). Hibiscus hareyae has high ornamental potential but is unknown in cultivation.

Key Words: Africa, conservation, coral rag, Hibiscus schizopetalus, horticulture

Hibiscus hareyae L.A.J.Thomson & Cheek.
A leaves and inflorescence from above showing epicalyces; B flower from below showing white inner petal markings. From Suleiman et al. 5526 (K).
photos: A. Iain Darbyshire, B. Toral Shah. 

Hibiscus hareyae L.A.J.Thomson & Cheek.
A habit, leafy shoot; B full-sized leaf, abaxial surface; C flowering shoot; D petal; E anther; F anther, inner face; G anther, dorsal face showing filament insertion; H pedicel, epicalyx and calyx; J pedicel detail-indumentum; K calyx margin – indumentum; L epicalyx lobe — indumentum.
From Milne-Redhead & Taylor 7481.
Drawn by Andrew Brown.  

Hibiscus hareyae L.A.J.Thomson & Cheek sp. nov. 

Type: Tanzania, Lindi Province, “Collected July 1877. Lindi, E. Africa, Lat. 9 40’ South this extends its habitats a little further South than before”, Kirk s.n. (holotype K00240493!) (Fig. 1).

RECOGNITION. Within Hibiscus, H. hareyae and H. schizopetalus are the only two species with laciniate petals. Hibiscus hareyae is readily distinguished from H. schizopetalus by its much shorter and non-articulated peduncle-pedicels (0.4 – 2 cm long vs 8 – 14 cm long and articulated); longer and broader epicalyx bracts, (1.5 – 4 × 1 – 1.2 mm vs 0.6 – 1.5 × 0.1 – 0.3 (0.5) mm, the epicalyx forming a shallow cup 0.5 – 1 × 2 – 3 mm, vs bracts appearing free (for additional diagnostic characters see Table 1).

ETYMOLOGY. The specific epithet honours Dr Hareya Fassil (12 Jan. 1968 – present) in recognition of her work on conservation of plant genetic resources and the roles of traditional plant-based medicines in Africa.

VERNACULAR NAMES. Mgongonyoka (Swahili) and Kinyoka (Yau) (both Litchfield 5457); 
Lindi hibiscus (English).

Lex A. J. Thomson and Martin Cheek. 2020.  Discovered Online: Hibiscus hareyae sp. nov. of sect. Lilibiscus (Malvaceae), Threatened in Coastal Thicket at Lindi, Tanzania. Kew Bulletin. 75: 51. DOI: 10.1007/s12225-020-09911-6