Xylopia africana (Bentham) Oliver, Fl. trop. Afr. 1: 30. 1868.

Johnson, David M. & Murray, Nancy A., 2018, A revision of Xylopia L. (Annonaceae): the species of Tropical Africa, PhytoKeys 97, pp. 1-252 : 33-36

1. Xylopia africana (Bentham) Oliver, Fl. trop. Afr. 1: 30. 1868. Fig. 9B-F, J, K

Melodorum africanum Bentham, Trans. Linn. Soc. 23: 477. 1862.

Xylopicrum africanum (Bentham) Kuntze, Revis. gen. pl. 1: 8. 1891.

Fissistigma africanum (Bentham) Merrill, Philipp. J. Sci. 15: 130. 1919. Type. CAMEROON. Southwest Region, Camer[oon] Mount., Feb 1862, G. Mann 1193 (lectotype, here designated: K! [000105591]; isolectotypes: GH-2 sheets! K! [000105592], P! [00169119], U! [0095511]).

Description.

Tree up to 20 m tall, d.b.h. ca. 30 cm, stilt roots emerging from the trunk up to 2 m above base. Twigs brown, fine appressed-pubescent, the hairs 0.2-0.3 mm long; nodes occasionally with two axillary branches. Leaf with larger blades 6.3-15.4 cm long, 2.9-7.9 cm wide, subcoriaceous to coriaceous, discolorous, much paler abaxially in vivo, obovate, occasionally oblong or elliptic, apex short-acuminate to cuspidate, the acumen 2-10 mm long, base cuneate and decurrent on petiole, glabrous adaxially, fine appressed-pubescent abaxially; midrib plane to slightly impressed adaxially, raised abaxially, secondary veins weakly brochidodromous, 10-13 per side, diverging at 60-65° from the midrib, raised on both surfaces, higher-order veins forming a conspicuous reticulum that is slightly raised adaxially and strongly raised abaxially; petiole 6.4-9 mm long, semi-terete or canaliculate, appressed-pubescent to glabrate. Inflorescences axillary, 1-2-flowered, when 2-flowered the pedicels arising side by side from the axil, appressed-pubescent; pedicels 6.4-10.5 mm long, 0.7-1.6 mm thick; bracts 2, one to either side of midpoint, persistent, 1.2-3 mm long, broadly ovate to semicircular, apex obtuse to rounded, lower bract usually bifid from tearing down the center as the inflorescence enlarges; buds broadly ovoid, apex obtuse. Sepals erect or slightly spreading at anthesis, 1/10-1/5-connate, 4.5-7 mm long, 4.6-5.5 mm wide, coriaceous, ovate to triangular, apex acute, appressed-pubescent abaxially. Petals yellow to yellow-orange in vivo; outer petals more or less erect at anthesis, 8.2-9.5 mm long, 3.0-4.5 mm wide at base, 6.2-7.1 mm wide at midpoint, fleshy, ovate, apex acute to nearly rounded, concave in basal half adaxially, appressed-pubescent except for glabrous adaxial concavity; inner petals more or less erect at anthesis, 5.9-8.3 mm long, 1-2.6 mm wide at base, 3-3.9 mm wide at midpoint, chartaceous, narrowly rhombic to elliptic, apex acuminate or acute, base with undifferentiated margin, pubescent at apex, with finer pubescence extending into upper portion of concavity and base of concavity glabrous adaxially, pubescent at apex but otherwise glabrous abaxially. Stamens 100-120; fertile stamens 1.6-2.9 mm long, oblong to clavate, apex of connective 0.4-0.6 mm long, shieldlike, overhanging anther thecae, erect-pubescent, anthers 5-9-locellate, filament 0.5-1 mm long; outer staminodes 1.3-1.8 mm long, wedge-shaped to quadrate, apex obtuse to truncate; inner staminodes 2.8-3.4 mm long, clavate, apex rounded; staminal cone 1.8-2.7 mm in diameter, 0.6-0.8 mm high, concealing only the bases of the ovaries, rim laciniate. Carpels 9-15; ovaries 1.6-2.1 mm long, linear-oblong, pubescent, stigmas connivent, 3.2-4.6 mm long, linear, verrucose toward base, glabrous. Torus flat, 3.4-4 mm in diameter. Fruit of up to 10 glabrate monocarps borne on a pedicel 10-18 mm long, 4-5 mm thick, glabrate; torus 8-16 mm in diameter, 5-8 mm high, depressed-globose. Monocarps reddish to purplish green with red endocarp in vivo, 6.6-10.5 cm long, 1.0-1.4 cm wide, ca. 1.1 cm thick, linear-oblong to cylindrical, occasionally slightly falciform, torulose, apex mucronate, the beak 1-1.5 mm long, base contracted into a stipe 10-18 mm long, 2.5-5 mm thick, verrucose and longitudinally wrinkled; pericarp ca. 0.8 mm thick. Seeds in a single row, lying parallel to long axis of monocarp, up to 5 per monocarp, 13-15 mm long, 9-10.5 mm wide, 8.5-9 mm thick, ellipsoid, broadly elliptic in cross-section, truncate at micropylar end, rounded at chalazal end, black, smooth, shiny, raphe/antiraphe plane, micropylar scar ca. 1.5 mm in diameter, circular; sarcotesta absent; aril blood-red in vivo, dull orange-brown when dried, brushlike, 8-10 mm in diameter, ca. 4 mm high, fleshy, granular.

Phenology.

Specimens with flowers have been collected October-March and in May, with buds in August and November, and with fruits in September-January, March, and May.

Distribution

(Fig. 10 ). Occurs in montane and submontane mossy forests at elevations of 900-2000 m in southeastern Nigeria, southwestern Cameroon, and on the islands of Bioko (Equatorial Guinea) and São Tomé ( São Tomé & Principe).

Local names.

No local names were reported for this species on specimen labels, but Focho et al. (2010) listed the name "Hweneta (Ghana)" as applied to this species in the Mt. Cameroon area of Cameroon; the name “hwentea” is used widely in Ghana for Xylopia aethiopica .

Additional specimens examined.

NIGERIA. Cross River: Obudu District, Obudu Plateau, 18 Mar 1964 (fl), Hopkins FHI 54307 (WAG); Ogoja Province, Sonkwala area of Obudu Division, grass plateau above Ikwette, 5200 ft, 28 Dec 1948 (fl, fr), Savory & Keay FHI 25179 (K); Northern Ranges, Obudu Ranch, SE State, ca. 5200', 4 Jan 1973 (fl), Lock GC43569 (K); Boshi Extension Forest Reserve, 6°20'N, 9°20'E, alt. ca. 1600 m, 23 May 1971 (fl, fr), van Meer 1768 (WAG-2 sheets). CAMEROON. North: Chaîne de Nkohom à 42 km SSW de Ndiki, 14 Nov 1983 (buds, fr), Nkongmeneck 580 (P).-Northwest: Gazette Bali Ngemba F. R., 5°48.02'N, 10°05.78'E, 1700 m, 14 Nov 2000 (buds, fr), Cheek 10527 (K, MO); West Division, Gazette Bali Ngemba F. R., 5°49'N, 10°05'E, 1600 m, Mantum, 5 Oct 2001 (fr), Onana 1825 (K), Onana 1835 (K); Bali Ngemba F. R., 5°49.59'N, 10°05.57'E, 1700 m, 9 Nov 2000 (bud), Tadjouteu 410 (K).-Southwest: Buea, 1906 (fl, fr), Deistel 154 (A, BM, P); without definite locality, s. d. (fr), Deistel 454 (GH); Buea, 1000 m, Lehmbach 41 (B); Buea, Lehmbach 137a (B, M); Monts Rumpi-Rata Mount, 1788 m, 2 km au SW de Dikome Balua, 35 km NNW Kumba, 24 Mar 1976 (fl, fr), Letouzey 14551 (K-2 sheets, MO, P, WAG); Buea, 3000 ft., Maitland 233 (K, PRC); Cameroon Mountain, Buea area, 3-4000', 1930 (fl, fr), Maitland s. n. (K); Mt. Cameroun, NW de Buèa, 13 Mar 1981 (st), Meijer 15378 (DSM, K, MO); southern slope of Mount Cameroon above Batoke, 4°08'N, 9°05'E, 900-2000 m, 9-20 Jan 1984 (fl), Thomas 2981 (K, MO); forest in the Rumpi Hills, near Dikome Balue, 4°53'N, 9°53'E, Mar 1984 (fl), Thomas 3305 (K, MO, P, WAG); savanna with forest galleries near Aguosho, 10 km SSW of Akwaya, 6°18'N, 9°28'E, 1200 m, 19-20 Mar 1985 (fl), Thomas 4554 (MO, P); Limbe District, Fako Division, Mt. Etinde, N face of N ridge, ca. 1220 m, 24 Oct 1992 (fl, fr), Wheatley 605 (P).-West: Route Batcha-Batschingou (22 km ESE Bafang), 23 Nov 1974 (fl, fr), Letouzey 13300 (K, MO-2 sheets, P, WAG); Region M’Bamileke [ “M’Bamileleke”], 19 Dec 1957 (fr), de Wit 7947 (WAG-3 sheets). EQUATORIAL GUINEA. Bioko: entre Moca y el cruce Luba-Riaba, 1400 m, (st), Fernández Casas 11693 (K); entre Moca y Riaba por el camino viejo, 1280 m, 20 Feb 1989 (fl, fr), Fernández Casas 11823 (K); entre Moca y el lago Loreto, 1510 m, 21 Feb 1989 (fl, fr), Fernández Casas 11884 (K); Finca Puente, carretera de Usola a Moná, km 17, 20 Jan 1947 (fr), Guinea 1658 (MO); Biao Peak Trail, Pt 128-Pt 130, 3.36272°S, 8.65264°E, 1500 m, 13 Mar 2007 (fl, fr), Luke et al. 11858 (K); Bioko Sul, Balacha North Trail, 3.3797°N, 8.6669°E, 1300 m, 28 Sep 2009 (fr), Luke 13606 (MO). SAO TOME & PRINCIPE. Vila José, NW of Ribeira Peixe, track between Vila José and Cão Grande, 150-250 m, 21 Jan 1980 (fl, fr), de Wilde et al. 220 (P, WAG-2 sheets); Island of St. Thomas, rec. Nov 1861 (fr), Mann s. n. (K-000199061, K-000199062, K-000199063, P-00169118 as Mann 1193); Ins. S. Thome in sinu Biafra, ad Fazenda do Monte Coffé, 1860 (fl, yg fr in drawing), Welwitsch 764 (BM).

Xylopia africana is most similar to Xylopia staudtii . It is a smaller tree that can be distinguished by its larger sepals, obtuse outer petal apices, and red arils on the seeds. Keay (1954-1958, 1989) indicated that the leaf veins of X. africana are dark crimson on the underside of the leaves, but this has not been reported by other collectors and we did not observe this characteristic in dried specimens. The label of Cheek 10527 described the fresh leaves as "nearly white below" and the leaves of dried specimens usually have a uniform tan color abaxially. Xylopia africana also resembles X. globosa , but has smaller obovate leaves, obtuse ovate outer petals, and lacks a keel on the abaxial surface of the inner petals.

Xylopia africana occupies a unique habitat among African Xylopia species, occurring in mossy submontane to lower montane forest, reaching elevations of 2000 m. Bryophytes attached to the branches of several collections of X. africana (particularly conspicuous on the specimen Nkongmeneck 580) suggest the high humidity of the forests in which it grows. Associated species at one site in Cameroon included Carapa grandiflora , Garcinia spp., Psychotria spp., and Syzygium staudtii (Letouzey 14551). Soils in the forests in which the plants grow are acidic and sandy, with variable mineral nutrient composition ( Fonge et al. 2013). Xylopia africana is a canopy tree confined to these forests and is one of many endemic plant species threatened by continued clearing of the forests for agriculture ( Onana and Cheek 2011, Fonge et al. 2013). It is one of the few Xylopia species with a distribution extending to islands in the Gulf of Guinea, where it occurs on Bioko and São Tomé. On the former, it is found at elevations above 1200 m, while the collection de Wilde et al. 220 from São Tomé gives an elevation of only 150-250 m and a habitat of "old secondary forest with remnants of primary forest."

The collection de Wit 7947 appears to be a mixed collection. Leaves in packets and some of the monocarps are X. africana , but some detached monocarps in packets have much smaller seeds oriented obliquely to the long axis of the monocarp and may be those of X. thomsonii , which was collected by de Wit as de Wit Herb. 7952 (WAG).

Bentham gave the type information as from "Island of S. Thomas off the West Coast , and Cameroon Mountain, at 4000 feet (G. Mann)." The specimen Mann 1193 at K (ex Herb. Hook., K-000105591) from the " Cameroon Mountain 4000 ft " locality, collected in Feb. 1862, has a flower and relatively small leaves, as well as sketches, presumably by Bentham, of stamens, carpels, and petals mounted on the sheet. This specimen is chosen as the lectotype. A second sheet at K (K-000105592), stamped Herb. Hook., is also numbered Mann 1193 from the same location and date, has flowers and relatively small leaves and is considered an isolectotype. The other sheets at Kew collected by Mann (K-000199061, K-000199062, and K-000199063) all labeled as having come from "St. Thomas," have no collection number, have leaves that are larger than those of the lectotype specimens, and have fruits .

There are two sheets at P. A sheet numbered 1193 and labeled Cameroon Mt, Mann, 1862, has fruits and larger leaves. A second sheet has a specimen with flowers and smaller leaves and a printed ticket giving the S. Thomas locality but no collection number. The two labels seem to have become reversed in the distribution of the duplicates. We consider the lectotype material to be the specimens with smaller leaves and flowers whatever collection number or locality may be indicated on the sheet, as they all seem to represent the same gathering .

Figures

Figure 9. Xylopia globosa and X. africana. A, G-I X. globosa A Leaf G Inner petal, abaxial view, showing keel H Inflorescence, showing four buds and one flower with petals fallen I Outer petal, adaxial view B-F, J, K X. africana B Seed, lateral view with most of aril appendages fallen C Four inflorescences D Seed, micropylar end view E Inner petal, abaxial view F Outer petal, adaxial view J Leaf K Fruit. A, G-I from Normand s. n. (P), B, D, E, F, J, K from Letouzey 14551 (WAG) C from Thomas 4554 (MO).

Figure 10. Distributions of Xylopia africana, X. globosa, and X. staudtii. Bolder lines represent country borders, fainter lines lakes and major rivers.