Sabdariffa aspera (Hook.f.) Mwachala & R.L.Barrett, 2025

Sabdariffa aspera (Hook.f.) Mwachala & R.L.Barrett View in CoL , comb. nov.

( Fig. 9 a, b View Fig .)

Hibiscus asper Hook.f. in W.J. Hooker , Niger Fl. 228 (1849). Type: Sierra Leone: Miss Turner s.n. (holo: K 000240763 ) .

? Hibiscus vanderystii De Wild., Bull. Jard. Bot. État. Bruxelles View in CoL 5: 35 (1915). Type citation: ‘ Kwango , juillet 1913, H. Vanderyst , n. 1377).’ Type: Angola: Kwango [Cuango River], July 1913, H. J. R . Vanderyst 1377 (holo: BR 0000008952387 ) .

? Hibiscus malangensis Baker f., J. Bot. View in CoL 77: 22 (1939). Type: Angola: Malange Province , River Cuango, near Xa-Sengue, ~ 1075 m, 5 Apr. 1937, A.W. Exell & F. A . Mendonça 274 (lecto, here designated: BM 014117362 ; isolecto: COI 00005060 About COI , LISC 000598 About LISC ) .

Descriptions and illustrations

Hooker and Bentham (1849, p. 228); de Wildeman (1915, p. 35); Baker (1939, p. 22); Sprague (1913, pp. 418–419); Wilson (1999, p. 68, in minor part, excl. fig. 2c);? Leistner (2008, p. 114); van der Burg (2013, pp. 57–59, fig. 16); Lee et al. (2014, pp. 275–276, fig. 1, 3a–f).

Typification

Baker (1939) cited material at BM and COI as the type of H. malangensis , therefore a lectotype may be selected. We here designate BM 014117362 as this specimen has a label stating, ‘type’, a copy of the protologue is attached to this sheet and the material is in fertile condition .

Notes

The boundaries between Sabdariffa aspera and S. cannabina have been a matter of contention in the literature, especially regarding the placement of synonyms under each name. Fryxell (1990) noted that S. cordofana (Turcz.) Mwachala & R.L.Barrett was likely the same as S. aspera (a view not supported here) and distinct from S. cannabina . Leistner (2008, p. 114) placed H. malangensis Baker f. under S. cannabina but accepted S. aspera . Mwachala (2009) included S. aspera and the associated synonyms under a broad concept of S. cannabina and this has been followed by POWO (see https://powo.science.kew.org/).

Wilson (1999) considered the presence of a white, woolly tomentum at the base of the calyx to be diagnostic for S. cannabina and absent in S. aspera , a conclusion we support. Van der Burg (2013) also considered the two species to be quite distinct, recognising S. aspera as native to Gabon, whereas S. cannabina is only cultivated there. Van der Burg (2013) states that S. aspera can be further distinguished by leaves with 3–5 lobes, the lobed margins being wavy, and the reddish sepals. Assignment of synonyms is made challenging by the considerable morphological variation expressed in the relevant specimens (especially leaf morphology but also calyx and indumentum characters) and further field-based studies are likely to be required to fully resolve these debates. The synonyms listed above do all appear to conform with van der Burg’s concept of S. aspera in lacking the woolly tomentum on the calyx.

Wilson (1999, p. 49) notes that several collections examined appear to be natural hybrids between S. aspera and S. cannabina . These specimens should be further investigated for hybridisation possibly resulting from S. cannabina being introduced into the range of S. aspera or whether these may actually represent a discrete taxon with ‘intermediate’ morphology.

We here consider Wilson’s (1999, p. 68) concept of S. aspera to apply mostly to S. cordofana and S. verrucosa , and only partially to the type concept of S. aspera . Although the delimitation of S. aspera , S. cordofana and S. verrucosa will require further study by local workers, we here distinguish S. aspera from these other two species based on whether the epicalyx lobes are ±flat when dry ( S. aspera ) or have distinct marginal ribs ( S. cordofana and S. verrucosa ). The typical form of S. aspera appears to have epicalyx lobes that are almost as long as the calyx lobes at anthesis (v. ~1/2 the length in related taxa). We also tentatively list synonyms under S. aspera based on the same character states, noting that several of these may well warrant recognition as discrete taxa but resolution of these matters is beyond the scope of the current study. We note as an example that specimens at P identified as Hibiscus asper (as at April 2024) are a mix of S. aspera , S. cannabina , S. cordofana and S. verrucosa , with occasional specimens of other species including S. elongatifolia (Hochr.) Mwachala & R.L.Barrett. We have included Hibiscus malangensis and H. vanderystii De Willd. in the key to African species below under those names to encourage further study of these poorly known taxa.

M.Pobegun 1032 from Guinae (P 06721267) notably has deeply lobed lower leaves and simple, almost linear leaves subtending the flowers. A specimen from the Democratic Republic of The Congo (J.Koechlin JK3715; P 06721279) also has simple leaves subtending the flowers.

Specimens from Madagascar previously assigned to S. aspera (e.g. P.B.Phillipson et al. 3890; MO, P 00554877) may represent a distinct new species endemic to Madagascar.

Future studies should investigate consistency of the calyx length relative to the ovary length at anthesis, calyx indumentum (including glands and aculei), corolla colour and relative variation in leaf lobing at different growth stages (e.g. basal v. climax leaves) including lobe margins).

Distribution

Based on examination of specimens at P, S. aspera as defined here occurs in Cameroon, Côte d’Ivoire, Guinae, Liberia, Mali, Mauritania, Niger, Senegal, Sierra Leone and possibly extends south as far as Angola.