Xylopia mwasumbii D. M. Johnson, Novon 9: 55-58. 1999.

Johnson, David M. & Murray, Nancy A., 2018, A revision of Xylopia L. (Annonaceae): the species of Tropical Africa, PhytoKeys 97, pp. 1-252 : 75-79

10. Xylopia mwasumbii D. M. Johnson, Novon 9: 55-58. 1999. Figs 18G, I-P

Type.

TANZANIA. Dar-es-Salaam Region, Kisarawe District, Pugu Forest Reserve , along N road 0.5 km E of brick factory, 6°52'S, 39°06'E, 200 m, 16 Feb 1996, D. M. Johnson & H. J. Ndangalasi 1884 (holotype: OWU!; isotypes: DSM! K! MO! [217000]) .

Description.

Tree up to 9 m tall, d.b.h. up to 10 cm, often with multiple trunks, the principal trunk often arching rather than erect; bark white with gray and orange mottling, mostly smooth but exfoliating in patches. Twigs gray, sparsely appressed-pubescent, the hairs 0.2-0.4 mm long, eventually light gray to gray-brown, glabrate; nodes frequently with two or more axillary branches. Leaf with larger blades 4.6-8.7 cm long, 2.4-4.3 cm wide, subcoriaceous, concolorous but paler abaxially, broadly elliptic to elliptic, occasionally ovate, elliptic-ovate, or obovate-elliptic, apex blunt-acuminate with an acumen 4-8 mm long, occasionally obtuse and emarginate, base broadly cuneate and decurrent on petiole, glabrous adaxially, sparsely sericeous abaxially; midrib plane adaxially, raised and somewhat keeled abaxially, secondary veins weakly brochidodromous, 9-11 per side, diverging at 55-70° from the midrib, these and higher-order veins indistinct but raised adaxially, slightly raised abaxially; petiole 4.5-8 mm long, flattened to canaliculate adaxially, glabrous to sparsely appressed-pubescent. Inflorescences axillary or from the axils of fallen leaves, 1-3-flowered, sparsely pubescent to glabrate; peduncle 1 per axil or absent, 1.9-4 mm long; pedicels 1-2 per peduncle, 2.4-3.5 mm long, 0.8-1.6 mm thick; bracts 2-3, evenly spaced along pedicel, caducous to persistent, 0.8-1.6 mm long, ovate, quadrate, semicircular, or deltate, occasionally tearing down the center as the inflorescence enlarges, apex obtuse; buds ovate-lanceolate to lanceolate, apex obtuse. Sepals slightly spreading at anthesis, 1/4-1/2-connate, 1.4-2.2 mm long, 1.5-2.2 mm wide, coriaceous, elliptic, apex obtuse to acute, sparsely sericeous abaxially. Petals olive-yellow to white in vivo; outer petals spreading at anthesis, 8-10 mm long, 2-3 mm wide at base, 2.3-2.6 mm wide at midpoint, coriaceous to slightly fleshy, linear-lanceolate to narrowly triangular, apex acute, appressed-pubescent adaxially, sericeous abaxially; inner petals erect at anthesis, 5.7-7.5 mm long, 1.8-2.2 mm wide at base, ca. 2.0 mm wide at midpoint, coriaceous to slightly fleshy, lanceolate, apex acute, base with undifferentiated margin, glabrous or with a few hairs. Stamens 40-45; fertile stamens 1.5-1.8 mm long, narrowly oblong, apex of connective obtuse to truncate, not exceeding anther thecae, anthers 6-13-locellate, filament ca. 0.7 mm long; outer staminodes absent; inner staminodes absent, but sometimes innermost stamens only 3-4-locellate; staminal cone 0.8-0.9 mm in diameter, 0.4-0.5 mm high, concealing only the bases of the ovaries, rim laciniate. Carpels 2-4; ovaries 1.5-1.7 mm long, narrowly oblong, sericeous, stigmas slightly separated, 0.7-1.1 mm long, lanceolate-falcate, flattened and longitudinally grooved on inner surface, glabrous. Torus flat, 1.5-1.6 mm in diameter. Fruit of up to 3 sparsely pubescent to glabrate monocarps borne on a pedicel 4.5-6 mm long, 1.1-1.4 mm thick, sparsely pubescent to glabrate, with sepals and sometimes persistent; torus not expanded in fruit, obscured by sepals. Monocarps with yellow-green exterior marked with contrasting green raised venation in vivo, 2-2.7 cm long, ca. 1.1 cm wide, 0.4-0.5 cm thick, oblong, not or only weakly torulose, apex truncate, obliquely mucronate, the beak 1-2 mm long, base contracted into a stipe 5-8.5 mm long, 1.1-1.6 mm thick, with raised veins forming oblique ridges and otherwise slightly wrinkled and finely verrucose; pericarp 0.5-0.6 mm thick. Seeds 2-4 per monocarp, in a single row, lying oblique or perpendicular to long axis, 8.5-9 mm long, 5.5-6 mm wide, ca. 5.4 mm thick, ellipsoid, broadly elliptic in cross section, truncate at micropylar end, rounded at chalazal end, light brown, smooth, shiny, raphe/antiraphe plane, visible as a band encircling the seed, micropylar scar 2.2-2.5 mm long, 2.0-2.5 mm wide, elliptic to circular; sarcotesta absent; aril white in vivo, light brown when dried, cupular, 4-5 mm in diameter, 1.7-2.2 mm high, fleshy, smooth.

Phenology.

Specimens with flowers were collected from February to May, and with fruits from February to June. We observed no definable peak of flowering in the field but only a few flowers at anthesis were present at any time on a given tree during the flowering period. Similarly, very few fruits could be found on an individual tree at any one time. Vegetative growth seemed to have been stimulated by the short rains of November and December, with production of flower buds following shortly thereafter.

Distribution

(Fig. 19 ). Occurs in east-central Tanzania, in dry evergreen forest on small ridgetops and plateaus near the coast, with Scorodophloeus fischeri and Manilkara sulcata being frequent canopy associates; 0-300 m. Understory associates in the Pugu Forest Reserve include Lasiodiscus holtzii , Uvaria pandensis , Uvaria puguensis , and species of Hugonia , Hymenocardia , Landolphia , Ochna , and Suregada .

Local names.

Mgwaza, mgwaza dume (Kizaramo), mlambambulu (Kiswahili), nnoga (Kiswahili).

Additional specimens examined.

TANZANIA. Pwani: Ruvu South Forest, Kisarawe District , 6°58'S, 38°54'E, 260 m, 30 mi SW of Dar es Salaam, 12 Feb-14 Mar 1991 (fr), Frontier Tanzania 2128 (K); Pande, 20 Jul 1982 (st), Hawthorne 1360 (K), Hawthorne 1714 (K); Pande, W. edge, 19 Aug 1982 (buds), Hawthorne 1469 (K); Kisiju, by the sea, Hawthorne 1790 (DSM); Kisarawe District, Pugu Forest Reserve, ridges along north road between Pugu railway station and brick works, 6°52'30"S, 39°06'E, 29 Feb 1996 (fl, fr), Johnson & Mwasumbi 1899 (DSM, OWU); Kisarawe District , Pugu Forest Reserve , along N road 0.5 km E of brick factory, 6°52'S, 39°06'E, 2 Apr 1996 (fl, fr), Johnson 1920 (DSM, OWU), 24 Apr 1996 (fl), Johnson 1928A (OWU, spirit collection only); Kisarawe District , Pugu Forest Reserve , ridgetop over road tunnel, 6°52'30"S, 39°05'30"E, 6 May 1996 (fl), Johnson & Mwasumbi 1936 (DSM, OWU); Kisarawe District , Pugu Forest Reserve , S of Dar-Kisarawe road, ridgetop near Mwakanga railway station, 6°55'S, 39°06'E, 22 Jun 1996 (fl, fr), Johnson & Ndangalasi 1948 (DSM, OWU); Bagamoyo District , Zaraninge Forest Reserve , 54 km E of Hwy, 6°04-13'S, 38°35-42'E, 28 Jun 1996 (buds), Johnson & Mbago 1963 (DSM, OWU); Kisarawe District , Pugu Forest Reserve , bus roundabout area ca. 4 km E of Kisarawe, 06°53'30"S, 39°06'E, 29 Jun 1996 (fr), Johnson 1964B (DSM, OWU); Kisarawe District , Kazimzumbwi Ruvu South [sic], Magogo 618 (NHT, TFD); T6, Ruvu South Forest Reserve , Ufang'ombe area , 06°56'S, 38°49'E, 180 m, 30 Apr 2001 (st), Mwangoka & Saidi 2099 (MO); Kisarawe District : Banda Forest Reserve near Mfyoza village , 12 Nov 1969 (buds), Ruffo 301 (EA, K, NHT, TFD); Pande, Rulangaranga et al. 53 (K, MO); Kisarawe District , Pugu Forest Reserve , 10 Mar 1964 (buds), Semsei 3704 (EA, K, TFD); Kisarawe District , Banda Forest Reserve , 12 Nov 1969 (buds), Shabani 471 (EA, K, TFD); Pande Forest Reserve , 25 km WNW of Dar [es Salaam], 8 Feb 1975 (fl), Wingfield 3311 (DSM, EA, K) .

An inconspicuous plant, Xylopia mwasumbii , was first recognized as Xylopia "species B" by Verdcourt (1971b). It is most similar to X. tenuipetala from northeastern Mozambique, but the leaf blades are usually elliptic to broadly elliptic, with cuneate bases and blunt-acuminate to obtuse apices, the pedicels and petals are shorter, and the ovaries are pubescent. These two species have some of the lowest stamen numbers, 50 or fewer, of any African species.

For X. mwasumbii , we calculated an EOO of 3,702 km 2 and an AOO of 60 km 2; there are only four other African species with a smaller global distribution. It was categorized as Endangered in the IUCN Red List, version 3.1 ( IUCN Species Survival Commission 2012), with a conservation assessment of B1ab(iii), Decreasing. The dry evergreen coastal forests where Xylopia mwasumbii grows are still poorly known and very limited in extent. Within this rare forest formation, however, the species may be more common than is currently recognized: its green-tinted flowers and fruits are inconspicuous, and its principal flowering and fruiting occur largely during the long wet season. Xylopia mwasumbii also has a strong resemblance to species of Diospyros and, in herbarium material, to other genera of Annonaceae such as Sphaerocoryne and Toussaintia and may thus be misidentified in collections. The flower-galls, described by Verdcourt (1971b), seem to be a frequent feature of the species, and may be useful for field identification.

Figures

Figure 18. Xylopia lukei and X. mwasumbii. A-F, H X. lukei A Habit B, C Stamens, abaxial view D Outer petal, adaxial view E Inner petal, adaxial view F Flower, side view H Flower with petals removed, showing carpels G, I-P X. mwasumbii G Fruit I Leaves J Flower, side view K, M Stamens, abaxial view L Gynoecium and surrounding staminal cone N Flower gall O Seed with aril removed, side view P Seed with aril removed, view of micropylar end. A-F, H from Luke et al. 10166 (MO) G from Johnson & Ndangalasi 1899 (OWU) I, J from Johnson 1920 (OWU) K-M from Johnson 1928 A (OWU) N from Johnson & Ndangalasi 1948 (OWU) O, P from Johnson & Ndangalasi 1884 (OWU) K-M, O, P were drawn from ethanol-preserved material and so have dimensions slightly greater than those in the description, which is based on dried specimens. Reproduced with the permission of the Board of Trustees, Royal Botanic Gardens Kew.

Figure 19. Distributions of Xylopia lukei, X. mwasumbii, and X. tenuipetala in eastern Africa. Bold lines represent country borders.