New Species of Xylopia and Uvaria (Annonaceae) from Tanzania

Abstract

Two new species of Annonaceae from the threatened lowland coastal forests of Tanzania are described and illustrated. Xylopia mwasumbii D. M. Johnson has distinctive flattened monocarps, unique among its African congeners. Uvaria puguensis D. M. Johnson is a small-flowered species belonging to a complex including, in East Africa, U. angolensis, U. lucida, and U. tanzaniae. A key to the taxa of the U. angolensis group in East Africa is provided. Annonaceae are especially diverse in the lowland coastal forests of Tanzania and Kenya, with six genera and 35 species endemic to these forests (Verdcourt, 1971, 1986; Verdcourt & Mwasumbi, 1988; Vollesen, 1980). At the same time that the biological diversity of these coastal forests is being recognized, this rare forest formation is disappearing due to pressure from land development and charcoal production (Burgess et al., 1992; Mwasumbi et al., 1994). Pugu Forest Reserve near Dar es Salaam, Tanzania, is the best-studied coastal forest in Tanzania (Burgess et al., 1992), yet we have just recently gathered sufficient material to describe two new species of Annonaceae, one in Xylopia and one in Uvaria, from this small reserve and nearby areas. Both species occur in forested uplands with a distinctive suite of associated species, including Baphia puguensis Brummitt, Hugonia castaneifolia Engler, Hymenaea verrucosa Gaertner, Hymenocardia ulmoides Oliver, Landolphia kirkii Dyer, Lasiodiscus holtzii Engler, Manilkara sulcata (Engler) Dubard, Monanthotaxis fornicata (Baillon) Verdcourt, Nesogordonia holtzii (Engler) Capuron, Scorodophloeus fischeri (Taubert) J. Leon, Suregada zanzibariensis Baillon, and Uvaria pandensis Verdcourt, as well as species of Croton, Haplocoelopsis, Ochna, Megalochlamys, Rinorea, and Tessmannia. Verdcourt (1971), in his treatment of Xylopia for the Flora of Tropical East Africa, first drew attention to the specimen Semsei 3704 from the Pugu Forest Reserve, identifying it as Xylopia Species B and commenting, material is scarcely adequate for description and only one of the two specimens seen bears flowers; both bear globose artichoke-like galls covered with conical tubercles which appear to be derived from the flowers. The name Xylopia Species B has, in the meantime, crept into East African floristic literature (e.g., Hawthorne, 1993), but it is now possible to name and describe this species in detail. Xylopia mwasumbii D. M. Johnson, sp. nov. TYPE: Tanzania. Coast Region: Kisarawe District, Pugu Forest Reserve, along N road 0.5 km E of brick factory, 6?52'S, 39006'E, 200 m, 16 Feb. 1996, Johnson & Ndangalasi 1884 (holotype, OWU; isotypes, DSM, K, MO). Figure 1A-H. Inter africanas Xylopiae species petalis lanceolatis olivaceis, staminibus non-capitatis, staminodiis nullis, carpellis duobus vel tribus, stigmatibus glabris oblongo-falcatis, toro leviter tantum concavo, et monocarpiis foliiformibus falcatis venosis compressis distincta. Tree 4-9 m tall, DBH up to 8 cm, often with multiple trunks, the principal trunk often arching rather than erect; bark white with gray and orange mottling, exfoliating in places; slash brown on yellow (ex Hawthorne). Nodes occasionally with two or more axillary branches. Twigs 0.7-2.1 mm diam., gray, longitudinally wrinkled, with epidermis soon exfoliating, sparsely lenticellate, sparsely appressed-pubescent to glabrate, the simple hairs 0.2-0.4 mm long. Lamina of larger leaves 4.6-7.7 cm long, 2.4--4.3 cm wide, paler abaxially, subcoriaceous, broadly elliptic to elliptic, occasionally ovate, elliptic-ovate, or obovate-elliptic; base cuneate, decurrent on petiole; apex 4-8 mm long, blunt-acuminate, or occasionally obtuse and emarginate; lamina with adaxial surface glabrous, abaxial surface sparsely sericeous; midrib impressed to plane adaxially, abaxially raised and keeled; secondary veins 9-11 per side, departing at 50-600 from the midrib, weakly brochidodromous, anastomosing 1-2 mm from margin; secondary and highNovoN 9: 55-60. 1999. This content downloaded from 157.55.39.138 on Tue, 19 Apr 2016 04:43:31 UTC All use subject to http://about.jstor.org/terms