Xylopia tanganyikensis D. M. Johnson, Kew Bull. 72:11: 9-11. 2017.

Johnson, David M. & Murray, Nancy A., 2018, A revision of Xylopia L. (Annonaceae): the species of Tropical Africa, PhytoKeys 97, pp. 1-252 : 167-168

42. Xylopia tanganyikensis D. M. Johnson, Kew Bull. 72:11: 9-11. 2017. Figs 4H , 28F-O

Type.

TANZANIA. Kigoma Region, T4, Kigoma District, Mahali Mts. , 800-1500 m, s. d., T. Nishida 57 (holotype: K!; isotype: EA!) .

Description.

Tree up to 25 m tall, d.b.h. up to 20 cm; bark light gray, finely fissured or scaly. Twigs reddish brown to blackish brown, sparsely and finely pubescent, the hairs 0.2-0.6 mm long, eventually gray to gray-brown, sparsely pubescent to glabrate; nodes occasionally with two axillary branches. Leaf with larger blades 6.4-9.0 cm long, 1.8-2.8 cm wide, chartaceous, usually discolorous, gray adaxially, yellow-olive to tan and paler abaxially, lanceolate to elliptic, apex acute, acuminate, obtuse, or retuse and more or less mucronate, the acumen, if present, 6-11 mm long, base cuneate to broadly cuneate, glabrous except for the pubescent midrib adaxially, finely appressed-pubescent abaxially; midrib plane to slightly impressed adaxially, raised abaxially, secondary veins brochidodromous, 10-17 per side, diverging at 60-70° from the midrib, these and higher-order veins indistinct to slightly raised on both surfaces; petiole 2-4 mm long, shallowly canaliculate, pubescent. Inflorescences axillary, 1(-2)-flowered, sparsely pubescent; peduncle 1 per axil, 1.3-2.2 mm long; pedicels 1 per peduncle, articulated with peduncle, 1-1.5 mm long; 1.5-1.6 mm thick; bracts 2-3, evenly spaced along pedicel, caducous, 1.7-3.5 mm long, broadly ovate to semicircular, apex acute to rounded; buds linear, falciform, apex acute. Sepals slightly spreading to spreading at anthesis, 1/4-connate, 2-3 mm long, 2.8-3.2 mm wide, coriaceous or sometimes slightly fleshy at base, ovate to broadly ovate, apex acute or apiculate, densely sericeous abaxially. Petals of unknown color in vivo; outer petals slightly spreading at anthesis, 28-38 mm long, 3.8-3.9 mm wide at base, 1.4-1.8 mm wide at midpoint, coriaceous, linear, apex acute, puberulent on distal half and downward along the margins but otherwise glabrous adaxially, appressed-pubescent abaxially; inner petals curved outward from the base but with the tips incurved at anthesis, 27-31 mm long, 2.7-3.0 mm wide at base, 0.9-1.0 mm wide at midpoint, coriaceous, linear, apex acute, base with undifferentiated margin, grayish silver-pubescent on both surfaces. Stamens 140-170; fertile stamens 1.3-2.7 mm long, narrowly oblong, apex of connective 0.1-0.2 mm long, shieldlike, overhanging the anther thecae, finely papillate, anthers 9-11-locellate, filament 0.4-0.6 mm long; outer staminodes ca. 1.7 mm long, oblong to broadly clavate, apex rounded; inner staminodes 1.0-1.2 mm long, oblong, apex obtuse to truncate; staminal cone ca. 2.1 mm in diameter, 0.8-1 mm high, concealing all but apices of the ovaries, rim laciniate. Carpels ca. 11; ovaries ca. 1.2 mm long, oblong, pubescent, stigmas more or less discrete, 2.5-3.3 mm long, linear, glabrous except for an apical tuft of hairs. Torus flat, 2.0-2.7 mm in diameter. Fruit of up to 9 glabrate monocarps borne on a pedicel 5-16 mm long, 1.3-6 mm thick, sparsely pubescent to glabrate; torus 9-14 mm in diameter, 8-9 mm high, globose to depressed-globose. Monocarps with a green exterior and red endocarp in vivo, 3.0-5.4 cm long, 1.6-2.0 cm wide, 0.8-1.6 cm thick, obovoid to oblong-obovoid, not or only weakly torulose, apex rounded, base sessile or contracted into a stipe 2-10 mm long, 3.5-6 mm thick, finely verrucose; pericarp 0.5-0.7 mm thick. Seeds 3-7 per monocarp, in a single or irregular double row, lying oblique to perpendicular to long axis, 9.4-14.0 mm long, 6.9-9.2 mm wide, 6.2-8.4 mm thick, ellipsoid to oblong, irregularly elliptic to wedge-shaped in cross section, truncate at micropylar end, rounded at chalazal end, brown, smooth, slightly shiny, raphe/antiraphe not evident, micropylar scar 5-5.5 mm long, 3-4 mm wide, ovoid; sarcotesta pale gray, fleshy in vivo; aril absent.

Phenology.

The single flowering collection lacks a date. Flowering phenology information in Johnson et al. (2017) indicating flowering in March and April is an error. Specimens with fruits have been collected in February, April, and July.

Distribution

(Fig. 38 ). Known only from western Tanzania along or near Lake Tanganyika, growing in evergreen forest at 800-1600 m.

Local names.

Kafwibili (Kitongwe, Nishida 57), kahwibili (Itoh & Sakamaki NI97-62, Uehara 580), tunda-yai (Kibembe, Abeid et al. 1028).

Additional specimens examined.

TANZANIA. Katavi: Mpanda District, SW of Mwese village, Lubalisi Village , Mtakala Forest , Kuleba Hill Peak , 06°13 00 S, 030°18 00 E, 1600 m, 20 Jul 2001 (fr), Abeid et al. 1028 (L, MO) .- Kigoma: Mahale Mts., 860-880 m, 23 Feb 1998 (fr), Itoh & Sakamaki NI 97-62 (K); Mahale National Park , Ken’ichi Masni [Masui?] 2-20 (EA); T4 , Kigoma District, Mahali Mts., 800-1500 m, s. d. (fr), Nishida 51 (EA, K). T4, Lake Tanganyika , Mahale Mts. , Kasiha , 850 m, 25 Apr 1978 (fr), Uehara 580 (EA, K) .

Xylopia tanganyikensis has narrow discolorous leaves with appressed abaxial pubescence, short-pedicellate flowers with petals up to 38 mm long, and sessile monocarps widest at or beyond the middle and rounded at the apex. It resembles Xylopia elliotii of the Sahel and Sudanian regions in its discolorous leaves and oblong to obovoid monocarps with rounded apices, but the latter species is a smaller tree of gallery forest with longer flower pedicels and smaller monocarps. Xylopia tanganyikensis also resembles X. cupularis , but lacks the golden-sericeous abaxial leaf surface, longer pedicels, and long-stipitate monocarps of that species. Xylopia shirensis , with which it possibly overlaps in distribution, is a smaller tree of miombo ( Brachystegia spp.) woodland with broader and more pubescent leaves.

This is the easternmost species of the Xylopia acutiflora group. It is probably allied to the other members of the group with large ovoid or oblong monocarps, such as X. hypolampra and X. phloiodora , which share a tendency for the monocarp to split into three segments upon dehiscence.

Xylopia tanganyikensis has a proposed IUCN Conservation Assessment of Endangered B1ab(iii) + B2ab(iii), recognizing threats from habitat alteration despite the fact that it occurs within the protected area of Mahale Mountains National Park ( Johnson et al. 2017). The specimen Léonard 4713 (BR), from the eastern Democratic Republic of the Congo, may also represent X. tanganyikensis .

Figures

Figure 4. Fruits and seeds of representative Xylopia species. A Xylopia staudtii from Democratic Republic of the Congo B Xylopia aethiopica from Republic of the Congo C Xylopia quintasii from Cameroon D Xylopia tenuipetala from Mozambique E Xylopia collina from Mozambique F Xylopia gracilipes from Mozambique G Xylopia hypolampra from Gabon H Xylopia tanganyikensis from Tanzania. A by Quentin Luke B by David Harris C, G by Thomas L. P. Couvreur D by Jonathan Timberlake E, F by Mervyn Loetter H by Noriko Itoh. C reproduced with permission of Thomas L. P. Couvreur and of the American Society of Plant Taxonomists D reproduced with the permission of Jonathan Timberlake and of the Board of Trustees, Royal Botanic Gardens Kew.

Figure 28. Xylopia keniensis and X. tanganyikensis, with leaves of X. holtzii and X. longipetala for comparison. A Leaf of X. holtzii from Tanzania B Leaf of X. longipetala from Ghana C-E X. keniensis C Habit D Fruit E Inflorescence F-O X. tanganyikensis F Pedicel, sepals, and staminal cone G Base of inner petal, adaxial view H Base of outer petal, adaxial view I Flower, lateral view J Carpel K, L Habit M Stamen, abaxial view N Staminode, abaxial view O Fruit. A from Semsei 1718 (K) B from Jongkind & Nieuwenhuis 2130 (WAG) C, D from Luke & Robertson 2723 (MO) F-J, L-N from Nishida 57 (K) K, O from Abeid et al. 1028 (L). Reproduced with the permission of the Board of Trustees, Royal Botanic Gardens Kew.

Figure 38. Distributions of Xylopia cupularis and X. tanganyikensis. Bolder lines represent country borders, fainter lines lakes and major rivers.