Hibiscus

Thomson, Lex A. J. & Cheek, Martin, 2020, Discovered online: Hibiscus hareyae sp. nov. of sect. Lilibiscus (Malvaceae), threatened in coastal thicket at Lindi, Tanzania, Kew Bulletin 75 (4), pp. 3250-3252 : 2-3

Sect. Lilibiscus Hochr .

Shrubs, sometimes scandent, or small trees, usually with unlobed, ovate, glossy leaves. Flowers single, axillary, usually with an articulated peduncle. Involucre (epicalyx) of 5 – 10, more or less linear or narrowly triangular bracts, usually shorter than the calyx and never fused with each other or with the calyx. Calyx united into a tube, lobes shorter than tube. Involucre and calyx glabrous or only slightly tomentose with stellate and simple hairs. Corolla large and bright, the petals reflexed at anthesis leaving the staminal column conspicuously exserted. Fruit capsular, usually obovoid and glabrous or scabrous, but never woolly. Seeds smooth, verrucate, or hairy.

Section Lilibiscus , comprising 23 species (several of which have previously been treated as subspecies), is restricted mainly to islands in the Indian and Pacific Oceans. It is monophyletic and sister to Sect. Hibiscus according to Pfeil et al. (2002) although with poor sampling. According to Thomson & Braglia (2019), nine species are known from Hawaii, those with predominantly white flowers being H. waimeae A.Heller , H. hannerae O.Deg. & I.Deg. , H. arnottianus A.Gray , H. immaculatus Roe , H. punaluuensis Skotsb. and those with orange or red flowers being H. kokio Hillebr. ex Wawra , H. kahili C.N.Forbes , H. saintjohnianus Roe , H. clayii O.Deg. & I.Deg. Four species have been recorded from Fiji: H. storckii Seem. , H. bennettii , H. bragliae L.A.J.Thomson , H. macverryi L.A.J.Thomson & Braglia ( Thomson & Braglia 2019). Hibiscus cooperi Hort. has recently been confirmed growing in its native state in the interior of Erromango, Vanuatu (Joe James Rungu, pers. comm.).

In the Indian Ocean, four species ( Hibiscus boryanus DC. , H. fragilis DC. , H. genevii Bojer ex Hook. , H. liliflorus Cav. ) are known from the Mascarene Islands and from Madagascar five species ( H. bernieri Baill. , H. grandidieri Baill. , H. phanerandus Baker , H. perrieri Hochr. , H. liliastrum Hochr. ), while H. schizopetalus and H. hareyae , described in this paper, are restricted to the Indian Ocean coast of E Africa. Two taxa, H. rosa-sinensis and H. denisonii Hort. are only known from horticulture. Plants of section Lilibiscus , especially H. rosa-sinensis and its hybrids are the most commonly cultivated ornamentals of the genus.

Taxonomic Treatment

The lectotype of Hibicus schizopetalus (Dyer) Hook. f. is Kirk s.n. ( K!, chosen by Cheek (1989)) from Kenya ,

Mombasa District. This specimen (Kew barcode K00240991, lectotype) was a mixed collection, with a different element subsequently barcoded K000240492 on the same sheet. Furthermore, the area on the sheet coded K000240492 includes specimens which are a mixture of H. schizopetalus and H. hareyae sp. nov. The only material of H. hareyae on this sheet is the short leafless stalk with a single flower on a short peduncle at the top right of the specimen sheet. The handwritten location ‘Kilwa’ in the hand of Daniel Oliver, Keeper of the Kew Herbarium, appears misplaced on the sheet and ought to have been pointing to the floral fragment of H. hareyae in the top right corner, rather than to the undoubted specimen of H. schizopetalus .

Hibiscus hareyae although superficially similar to H. schizopetalus , is a distinctive and well-marked species. Whilst H. hareyae is closely related to, and shares many features including two distinctive floral traits with, H. schizopetalus — laciniate petals and pendant flowers — it differs in other taxonomically significant floral and foliar morphological characters ( Table 1 ). These differences with H. schizopetalus indicate that it warrants species-level recognition. The absence of an articulated floral stalk is unique in sect. Lilibiscus . The two species have an allopatric distribution with the nearest populations separated by a distance of about 400 km. Examination of specimens of H. hareyae from northern Tanzania indicated no evidence of morphological intermediates or gene exchange between populations of the two species.

The name Hibiscus schizopetalus is globally associated with plants of the Kenyan and northern Tanzanian species: this species is now widely planted throughout the tropics and subtropics, and also as a glasshouse/ indoor plant in cooler climates. Planted in gardens as an ornamental it can often persist and become locally naturalised. Naturalised populations deduced from this source were observed in Cameroon in 2007 and Guinea in 2012 (Cheek pers. obs). On the Tropicos website of herbarium specimens of wild plants, of the 38 listed of Hibiscus schizopetalus , 28 are from Central and South America where the species is definitely not native, as is the case also for the records from Gabon and Mozambique (Tropicos. org 2020). We consider that most of the few specimens of H. schizopetalus from central-eastern Tanzania are likely to be naturalised or old plantings of H. schizopetalus , on this basis. For example the label of one specimen of H. schizopetalus from central Tanzania (H. Breyne 5562, BR0000019387017) collected along the Dar es Salam – Morogoro road states that it was introduced and naturalised in gallery forest.

Cheek’ s (1989) rationale for choice of lectotype is sound and fortuitously minimises any disruption with continuing the existing use of the name Hibiscus schizopetalus .

Materials and Methods

The new species was first discovered by the first author by examining online images of herbarium specimens including the Kew Herbarium catalogue (continuously updated), and examining them for morphological disjunctions. Gross morphological measurements were initially made from these images. Finally, herbarium material at K was examined with a Leica Wild M8 dissecting binocular microscope fitted with an eyepiece graticule measuring in units of 0.025 mm at maximum magnification. The drawing was made with the same equipment with a Leica 308700 camera lucida attachment. Specimens or their high resolution images were inspected from the following herbaria: BM, DSM, EA, FTG, K, MO and P. Names of species and authors follow IPNI (continuously updated). The format of the description follows those in other papers describing new taxa of Hibiscus Sect. Lilibiscus e.g. Thomson & Braglia (2019), Cafferty & Cheek (1996), Cheek et al. (1998). Technical terms follow Beentje & Cheek (2003). Specimens cited which have been seen are indicated “!”. The conservation assessment follows the IUCN (2012) categories and criteria. Herbarium codes follow Index Herbariorum (Thiers, continuously updated). The map was made using simplemappr software (https://www.simplemappr.net/).

New Species