Xylopia nilotica D. M. Johnson & N. A. Murray, 2018

Johnson, David M. & Murray, Nancy A., 2018, A revision of Xylopia L. (Annonaceae): the species of Tropical Africa, PhytoKeys 97, pp. 1-252 : 103-104

19. Xylopia nilotica D. M. Johnson & N. A. Murray sp. nov. Fig. 29

Diagnosis.

Species resembling Xylopia holtzii in its branched inflorescences and leaf blades adaxially hairy, but differing in the higher-order veins of the leaf equal in prominence to the secondary veins and forming a conspicuous raised reticulum on the adaxial surface, and the monocarps conspicuously verrucose but not much wrinkled, with stipes 3.5-5 mm thick.

Type: UGANDA. Northern Region, Leya and Aiyu river junction, W. Madi, 25 Mar 1945, P. J. Greenway & W. J. Eggeling 7251 (holotype: EA!; isotypes: K! PRE!).

Description.

Tree up to 25 m tall with a narrow crown, bole straight, fluted with small sharp buttresses at the base; bark light gray to grayish brown, sometimes exfoliating in irregular patches. Twigs brown to reddish brown, brownish gray, or blackish brown, sparsely pubescent, the hairs 0.2-0.5 mm long, eventually brownish black to dark gray, glabrate; nodes occasionally with two axillary branches. Leaf with larger blades (4.1-) 6.1-9.4 cm long, 2.2-3.2 cm wide, chartaceous, concolorous, oblong to lanceolate-oblong, apex obtuse to rounded, occasionally retuse or emarginate, base obliquely cuneate to rounded, sparsely pubescent (densest on the midrib) to glabrous adaxially, sparsely appressed-pubescent abaxially; midrib slightly raised to plane adaxially, raised abaxially, secondary veins weakly brochidodromous, 8-13 per side, diverging at 40-70° from the midrib, these and higher-order veins raised on both surfaces; petiole 3.5-8 mm long, semi-terete to shallowly canaliculate, pubescent. Inflorescences axillary, 1-3-flowered, pubescent; peduncle 1 per axil, 2.0-5.5 mm long; pedicels 2-3 per peduncle, (1.0-) 2.5-7.5 mm long, 0.5-0.9 mm thick; bracts 2, at or just distal to the pedicel midpoint, caducous or the uppermost persistent, ca. 1.6 mm long, broadly ovate, apex obtuse; buds linear-lanceolate, slightly falciform, apex acute, base globose. Sepals slightly spreading at anthesis, 1/3-1/2-connate, 1.5-2.5 mm long, 2.2-3.3 mm wide, coriaceous, semicircular to broadly triangular, apex acute, pubescent abaxially. Petals pale green to yellow-green in vivo; outer petals erect to somewhat spreading at anthesis, 11.7-27 mm long, 2.3-2.9 mm wide at base, 1.0-1.2 mm wide at midpoint, coriaceous, linear, apex acute, longitudinally ridged on abaxial surface, gray-puberulent except for glabrous base adaxially, golden-pubescent abaxially; inner petals curved outward or weakly geniculate at anthesis, 11.5-16.8 mm long, ca. 2.4 mm wide at base, ca. 0.7 mm wide at midpoint, coriaceous, linear-subulate, apex acute, base with undifferentiated margin, longitudinally ridged on both surfaces, densely puberulent on both surfaces except for the glabrous base. Stamens ca. 70-80; fertile stamens 1.0-1.3 mm long, narrowly oblong, apex of connective 0.1-0.2 mm long, depressed-globose to shieldlike, overhanging the anther thecae, glabrous, anthers 8-11-locellate, filament 0.3-0.5 mm long; outer staminodes 1-1.3 mm long, broadly clavate, apex rounded to truncate; inner staminodes 0.8-1 mm long, clavate, apex truncate; staminal cone 0.8-1.9 mm in diameter, 0.7-1.1 mm high, concealing only the bases of the ovaries, rim even to laciniate. Carpels ca. 7; ovaries 0.8-0.9 mm long, narrowly oblong, pubescent, stigmas loosely connivent, 2-2.5 mm long, linear, apices pubescent. Torus flat, 1.6-2.7 mm in diameter. Fruit of up to 12 sparsely pubescent monocarps borne on a pedicel 7-8.5 mm long, 2.5 mm thick, glabrate; torus 5-7.5 mm in diameter, 5.5-7 mm high, globose to depressed-globose. Monocarps 2.3-4.2 cm long, 0.9-1.3 cm wide, ca. 1.2 cm thick, oblong, weakly torulose, apex obtuse to rounded and somewhat flattened, base contracted into a stipe 6-9 mm long, 3.5-5 mm thick, obliquely wrinkled, strongly verrucose; pericarp 1 mm thick. Seeds up to 3 per monocarp, in a single row, lying oblique to long axis, 11.8-12.5 mm long, ca. 6.7 mm wide, ca. 5.8 mm thick, oblong-ellipsoid, semicircular in cross-section, narrowed and truncate at micropylar end, rounded at chalazal end, brown, smooth, shiny or dull, raphe/antiraphe not evident, micropylar scar ca. 2 mm long, ca. 1.5 mm wide, elliptic; sarcotesta red to orange in vivo; aril absent.

Phenology.

Specimens with flowers have been collected from February to May and in July, and with fruits from March to May.

Distribution

(Fig. 26 ). Occurs in upland and lower montane semideciduous forests, one specimen from along a river, in central Sudan, South Sudan, and northern Uganda, all from the upper Nile River watershed, at elevations between 760 and 1220 m.

Local names.

Kharûm (Eliri Arab, Simpson 7778), munnu (Anuak, Simpson 7778).

Additional specimens examined.

SUDAN. Gebel Amira, Nuba Mts., 16 Apr 1930 (buds), Simpson 7778 (K-2 sheets); Eastern KMagnolialesfan Province , Jebel Dair , 4000 ft, 17 Jul 1937 (fl), Turner 241 (K) . SOUTH SUDAN. West Equatoria: "Large tree of Azza," [ Azza forest is probably SE of Maridi, I. Darbyshire, personal communication, 2016], 28 Apr 1933 (fr), Smith 39 (K) . UGANDA. West Nile, Koich River, Rumogi , Mar 1935 (fl), Eggeling 1650 (K); Madi , 830 m, Feb 1961 (fl), Philip 931 (EA, K); Murchison Falls National Park , Rabongo Forest , 02°06'N, 31°52'E, 1020 m, 1 May 1993 (fl, fr), Sheil 1443 (K); Busoga District , Igwe mutalla, 10 mi S of Bugiri, 1260 m, 20 May 1951 (fl), Wood 610 (EA, K-2 sheets) .

Xylopia nilotica is most similar to X. holtzii of coastal Kenya and Tanzania, but is distinguished by the more prominent and raised reticulum of the adaxial leaf surface, with the higher-order veins equal in prominence to the secondary veins, and the strongly verrucose monocarps with thicker stipes. While Xylopia nilotica is more similar to X. holtzii than to X. longipetala , it is nearer to the latter geographically, differing in being a large forest tree of upland or even submontane forest rather than a riparian shrub or small tree, and in having much shorter petals and distinctly stipitate monocarps.

Xylopia nilotica occupies the northernmost distribution of any Xylopia species in Africa. Associates occurring at more than one locality include Holoptelea grandis , Milicia excelsa , and species of Khaya . Several sterile specimens probably represent this species: SUDAN: Broun & Broun 1373 (K), Longe 40, local name dooru (K), Myers 10102 (K); ETHIOPIA: Chaffey & Thomerson 658, local name orowyee (Anuak) (EA, K), Friis et al. 2485 (K).

Figures

Figure 26. Distributions of Xylopia shirensis, X. odoratissima, X. holtzii, X. gracilipes, X. nilotica, and X. torrei. Bolder lines represent country borders, fainter lines lakes and major rivers.

Figure 29. Xylopia nilotica. A Close-up of inflorescence, showing two pedicels branching from the same peduncle B Flower bud, lateral view C Receptacle with petals, stigmas, and most of the stamens fallen, showing staminal cone D Base of outer petal, adaxial view E Base of inner petal, adaxial view F Fertile stamen, abaxial view G Outer staminode, abaxial view H Leaf I Habit, including leaves and fruit J Seed, view of micropylar end and side view. A, H from Greenway & Eggeling 7251 (K) B from Wood 610 (K) C-G from Philip 931 (K) I from Greenway & Eggeling 7251 (PRE) J from Smith 39 (K).