1 Uapaca kirkiana (Phyllanthaceae) and its relatives in the northwest of the Zambezian region Pierre Meerts1,2 & João Farminhão1 1 Herbarium et bibliothèque de botanique africaine, Université Libre de Bruxelles, Avenue F.D. Roosevelt 50, CP 265, B-1050 Bruxelles, Belgium. 2 email: [email protected] Link to published version: Kew Bulletin 74 https://doi.org/10.1007/s12225-019-9826-1 2 Summary. The complex of Uapaca kirkiana is revised in the northwest of the Zambezian region (Angola, D. R. Congo, Zambia) based on herbarium taxonomy. Five taxa are recognised, i.e. Uapaca kirkiana Müll. Arg. var. kirkiana, U. kirkiana var. gossweileri (Hutch.) Meerts, U. kirkiana var. benguelensis (Müll. Arg.) Meerts, U. teusczii Pax f. teusczii and U. teusczii f. pilosa (P. A.Duvign.) Meerts. A determination key is provided. Specimens lacking curly hairs on leaves have long been misinterpreted or overlooked. The name Uapaca teusczii Pax is resuscitated to accommodate such specimens. New diagnostic characters of U. teusczii are highlighted including a glabrous ovary, anthers with ciliate connectives and the pubescent calyx of female flowers. U. teusczii is a characteristic species of the wet miombo, widespread in Katanga and Kwango (D. R. Congo), extending locally to Angola and N Zambia. A lectotype is selected for U. albida, U. homblei, U. kirkiana var. benguelensis, U. kirkiana var. gossweileri, and U. teusczii f. pilosa; second-step lectotypification is provided for U. munamensis. Key Words. Angola, edible fruit, D. R. Congo, miombo, taxonomy, dry tropical woodland, Zambia. Introduction The genus Uapaca Baill. (Baillon 1858) (Phyllanthaceae, Antidesmatoideae) comprises dioecious trees and shrubs, widespread in forests of tropical Africa and Madagascar. Uapaca species are amongst the most typical components of the shrub layer of dry tropical woodlands and savannahs in the Zambezian region (Werger & Coetzee 1978; White 1983). Uapaca kirkiana Müll. Arg., the most widespread species in that region, is well known for its edible, much sought fruits locally known as “masuku” (Akinnifesi et al. 2006; Ngulube et al. 1996). Domestication of Uapaca kirkiana has been successfully attempted, and breeding programs 3 are being developed (Ngulube et al. 1996; Akinnifesi et al. 2006; Mwase et al. 2015). In this context, improving the taxonomic knowledge of the species and its relatives is essential. Müller Argoviensis (1864a,b) described two species to accommodate specimens of Uapaca with foliar indumentum consisting of curly, interlacing hairs i.e. Uapaca kirkiana Müll. Arg. and U. benguelensis Müll. Arg. The former name is based on a type from Malawi and the latter, published a few days later, is based on a type from Angola. Ever since, the taxonomy and nomenclature of that complex have been confusing. Pax (1904) accepted both species, but did not indicate discriminant characters, the two species being separated based on geographical distribution. Hutchinson (1912a) pointed out that the original material on which the name U. benguelensis is based, i.e. Welwitsch 453, was heterogeneous, comprising two distinct taxa, i.e. one with petiolate leaves and the other one with sessile leaves. He described the latter as a new species, U. gossweileri Hutch., thus implicitly restricting U. benguelensis to petiolate forms. All three species (U. kirkiana, U. benguelensis, U. gossweileri) were accepted by Hutchinson (1912b) and Pax & Hoffmann (1922). The latter work distinguished U. kirkiana from U. benguelensis based on the lower number of secondary veins and the subsessile inflorescence of the latter. De Wildeman (1936) recognised several other taxa supposedly endemic to D. R. Congo in this complex, which were later synonymised with U. kirkiana or U. benguelensis by Duvigneaud (1949). In his revision of the genus for Katanga (D. R. Congo), Duvigneaud (1949) considerably extended the circumscription of U. benguelensis, to include forms with glabrous leaves and forms with straight hairs. Having re- examined alleged differences between U. benguelensis and U. kirkiana, Radcliffe-Smith (1993) concluded that there was considerable overlap between them and, accordingly, he synonymised both names under U. kirkiana. However, in his subsequent treatment of the genus Uapaca in Flora Zambesiaca, Radcliffe-Smith (1996) admitted that the question was not settled yet and that there might actually be two distinct species. The African Plant 4 Database (consulted in Aug. 2018) treats U. benguelensis as a synonym of U. gossweileri (which is certainly incorrect from a nomenclatural point of view), and U. benguelensis var. pedunculata as a synonym of U. kirkiana. The Plant List (http://www.theplantlist.org), in contrast, accepts U. benguelensis as a distinct taxon. The World Checklist of Selected Plant Families (http://apps.kew.org/wcsp/qsearch.do?plantName=Uapaca&page=quickSearch) also recognises U. benguelensis, U. gossweileri, U. kirkiana at species level. We here revise the taxonomy of this group, considering material from Angola, D. R. Congo and Zambia, the region which concentrates most of the variation in the complex. Five taxa are recognized, and four new combinations are proposed. Materials and methods We have revised the material from D. R. Congo, Angola and Zambia kept in the following herbaria: BM, BR, BRLU, COI, K, LSHI, LISC, LISU, P, POZG, WAG. The following characters, used in previous taxonomic treatments, were recorded: twig thickness and pubescence; leaves: petiole length, lamina length and width, shape of lamina base and apex, indumentum (curly vs. straight hairs; density), number of secondary veins; inflorescence: position respective to leaves; length of male and female peduncle, length of bracts; fruits: peduncle length and diameter, fruit diameter, indumentum, length and width of pyrenes. For the sake of simplicity, male and female inflorescences are hereafter referred to as “flowers”. For D. R. Congo, the specimens are grouped according to the phytogeographic divisions of Robyns (1948). Within each country, provinces or regions are cited in alphabetic order. 5 Key to the taxa of the Uapaca kirkiana complex in NW of the Zambezian region 1. Ovary glabrous or with sparse straight hairs; anthers with connective ciliate; lower surface of lamina of mature leaves glabrous or with straight hairs (occasionally with sparse remains of curly hairs on veins); lamina with 7 – 12 (– 13) pairs of secondary veins; tube of female calyx setulose, with hairs persisting at the fruiting state 2 1. Ovary densely tomentose, with curly hairs; anthers with connective usually glabrous; lower surface of lamina pubescent, with indumentum consisting of curly hairs not restricted to veins; lamina with (8– ) 12 – 25 pairs of secondary veins; female calyx generally glabrous when in fruit, or with curly hairs mostly at margin 3 2. Lower surface of leaf blade glabrous Uapaca teusczii f. teusczii 2. Lower surface of leaf blade with straight hairs Uapaca teusczii f. pilosa 3. Leaves grouped in a rosette at the apex of twigs, sessile, long attenuate at base into a winged pseudopetiole; second year’s twigs (8 –) 10 – 25 mm in diam., generally corky and marked by prominent leaf scars Uapaca kirkiana var. gossweileri 3. Leaves not grouped in a rosette at the end of twigs, generally petiolate, occasionally sessile, cuneate, not attenuate in a winged pseudopetiole; second year twigs generally < 10 mm in diam., not corky 4 4. Male flower head stipitate; male inflorescence globose before anthesis; inflorescences (male and female) and fruits generally borne 5 – 30 cm below the leaves on defoliated previous year’s twigs; male peduncles 5 – 20 mm long, mostly in fascicles of 2 – 9; lamina with (12 –) 13 – 21 (– 25) pairs of secondary veins Uapaca kirkiana var. kirkiana 4. Male flower head sessile; male inflorescence longer than wide before anthesis; inflorescences (male and female) and fruits mostly amongst the leaves on current year’s 6 growth; male peduncles 1 – 10 mm long, mostly solitary; lamina with 8 – 13 (– 14) pairs of secondary veins Uapaca kirkiana var. benguelensis Taxonomic Treatment 1. Uapaca teusczii Pax (1894: 79); Pax (1904: 371); Hutchinson (1912b: 641); Pax & Hoffmann (1922: 301); De Wildeman (1936: 179). Type: Angola, Malange, Teuscz 423 (holotype B; isotype K!). Uapaca angolensis Hutch. in schedis, unpublished name. Uapaca benguelensis var. pedunculata P. A.Duvign. (Duvigneaud 1949: 890). Type: D. R. Congo, Haut-Katanga, entre Elisabethville [Lubumbashi] et Katofio, Duvigneaud 1214U3 (holotype BRLU!; isotype FHO), synon. nov. Uapaca benguelensis sensu White (1962: 206), Malaisse (1997: 68), Meerts (2016: 238), Meerts & Hasson (2016: 183) non Müll. Arg. Small tree 2 – 5 (– 7) m high. Twigs 5 – 10 mm diam. below the lowermost leaf, blackish- gray, often with a silvery shine, generally glabrous except apical bud and at insertion of peduncles, more rarely shortly rusty-beige crisped pubescent near tip. Leaves with petiole 1.5 – 4.5 (– 5.5) cm, terete or flat on upper surface, glabrous or, more rarely, thinly puberulent to floccose (short, undulate hairs), epidermis lepidote generally flaking of in thin silvery scales; leaf blade (6.6 –) 9 – 19 (– 22) × (4.5 –) 6.6 – 14 (– 18) cm, broadly elliptic, obovate, obovate-elliptic, suborbicular to almost obcordiform, with length to width ratio typically ≤ 1.5, cuneate to rounded at base, broadly rounded to truncate or, more rarely, emarginate at apex; upper surface glabrous (rarely with remains of hairs on main nerve), lepidote, markedly glutinous