Xylopia keniensis D. M. Johnson, Kew Bull. 72:11: 10-12. 2017.

Johnson, David M. & Murray, Nancy A., 2018, A revision of Xylopia L. (Annonaceae): the species of Tropical Africa, PhytoKeys 97, pp. 1-252 : 100-102

18. Xylopia keniensis D. M. Johnson, Kew Bull. 72:11: 10-12. 2017. Fig. 28C-E

Type.

KENYA. Kwale District, Shimba Hills , 4.2407°S, 39.4218°E, 390 m, 30 Dec 2009, Q. Luke & P. Luke 13949 (holotype EA!; isotypes BR, K! MO! [6467367, 6569824], NHT, PRE, US).

Description.

Tree 15-25 m tall with long straight bole and rounded crown. Twigs greenish brown to blackish, glabrous or initially short-pubescent, the hairs 0.1-0.3 mm long, but soon light gray, glabrate; nodes occasionally with two axillary branches. Leaf with larger blades 6.7-10.5 cm long, 2.6-3.7 cm wide, chartaceous, shiny adaxially, dull and paler abaxially, lanceolate to elliptic, occasionally oblong or elliptic-oblanceolate, apex sharply acuminate, the acumen 6-18 mm long, occasionally obtuse, base cuneate to rounded, glabrous or with a few hairs at the base of the midrib adaxially, sparsely appressed-pubescent to glabrate abaxially; midrib slightly raised to plane adaxially, raised abaxially, secondary veins weakly brochidodromous, 12-15 per side, diverging at 60-75° from the midrib, these and higher order veins slightly raised on both surfaces; petiole 2-5.5 mm long, shallowly canaliculate, pubescent to glabrous. Inflorescences axillary, usually from the axils of fallen leaves, 1- or rarely 2-flowered, sparsely pubescent; pedicels 2.8-3.9 mm long, 0.6-0.7 mm thick; bracts 2, attached to the distal half of the pedicel, persistent or not, 1.2-1.6 mm long, broadly ovate to crescent-shaped, apex acute; buds lanceolate, apex acute. Sepals erect to slightly spreading at anthesis, 1/3-connate, 2.2-2.7 mm long, 2.3-2.4 mm wide, subcoriaceous, broadly ovate to triangular, apex obtuse to acute, sparsely pubescent abaxially. Petals cream-colored with reddish pink bases at anthesis in vivo; outer petals erect or slightly spreading at anthesis, 13.7-19.3 mm long, 2.2-2.6 mm wide at base, 0.9-1.0 mm wide at midpoint, coriaceous, linear, flat on both surfaces, apex obtuse, densely puberulent except for the glabrous warty base adaxially, golden-sericeous abaxially; inner petals geniculate at anthesis, with the apices bent sharply outward between the outer petals, 11.0-16.3 mm long, 1.8-2.2 mm wide at base, ca. 0.5 mm wide at midpoint, coriaceous, linear-subulate, longitudinally ridged on both surfaces, transversely thickened at widest point adaxially, apex acute, base with undifferentiated margin, densely puberulent on both surfaces except for the glabrous base. Stamens ca. 85; fertile stamens 1.0-1.3 mm long, narrowly oblong, apex of connective reddish pink at anthesis in vivo, 0.2-0.25 mm long, shieldlike, overhanging the anther thecae, smooth or finely papillate, anthers 7-10-locellate, fila ment 0.3-0.5 mm long; outer staminodes 1.2-1.5 mm long, oblong, apex rounded to truncate, sometimes emarginate; inner staminodes 1.0-1.1 mm long, oblong, apex truncate; staminal cone ca. 1.3 mm in diameter, 0.7 mm high, concealing only the bases of the ovaries, rim laciniate. Carpels ca. 6; ovaries ca. 0.3 mm long, oblong, pubescent; stigmas connivent, free at the apices, 1.8-2 mm long, filiform, apex acute, with a few hairs at the apices. Torus flat, ca. 1.8 mm in diameter Fruit of up to 4 glabrate monocarps borne on a pedicel ca. 5 mm long, ca. 2.6 mm thick, glabrate; torus ca. 4 mm in diameter, ca. 4.5 mm high, globose. Monocarps with a green exterior and red endocarp in vivo, 2.8-3.5 cm long, 1.0-1.6 cm wide, 1.1-1.4 cm thick, clavate-pyriform to ovoid, usually with a longitudinal ridge running down one side, apex obtuse, base tapered but not stipitate, verrucose; pericarp 0.4-1.0 mm thick. Seeds 4-6 per monocarp, in two rows, lying perpendicular to long axis, 11.0-11.2 mm long, 7.2-7.3 mm wide, ca. 5.1 mm thick, oblong to ellipsoid, obovate to elliptic in cross-section, obliquely truncate at micropylar end, rounded at chalazal end, dark brown, slightly wrinkled/roughened, dull, raphe/antiraphe not evident, micropylar scar ca. 3 mm long, 1.5 mm wide, elliptic; sarcotesta orange-red in vivo; aril absent.

Phenology.

Specimens with flowers or flower buds have been collected in November and December, and with fruits in March and September.

Distribution

(Fig. 22 ). Endemic to the Shimba Hills region of southern Kenya, where it grows in lowland forest at elevations of 350-430 m ( Luke 2005). Associates at one site (from Luke & Robertson 2723) included species of Antiaris , Milicia , Lovoa , Celtis , Quassia , Hymenaea , Julbernardia , and Manilkara in the canopy, and Leptonychia , Diospyros , Warneckea [ Memecylon ], and many Rubiaceae shrubs in the understory.

Additional specimens examined.

KENYA. Kwale: Shimba Hills, Makadara , 4.2394 S 39.3937 E, 430 m, [typed label gives locality as Taita Hills, which is a transcription error (R. Faden, personal communication)], 9 Nov 1970 (buds), Faden et al. 70/847 (K); Shimba Hills, Longomwagandi , 4.2407 S 39.42181 E, 390 m, 30 Dec 2009 (st seedling), Luke & Luke 13950 (EA); Shimba Hills, Longomwagandi, 4.2351 S 39.4181 E, 390 m, 17 March 1991 (fr), Luke & Robertson 2723 (EA, K, MO); Shimba Hills, 1 Jul 2006, Project Mbegu 353 (EA); Shimba Hills, 20 Jul 1967 (st), Mulwa 015 (EA) ; Kwale District, Shimba Hills, Lango ya Mwagandi or Longo Mwagandi Forest , 4.2333 S, 39.4167 E, 350 m, 18 Sep 1982 (fr), Polhill & Robertson 4800 (K) .

Xylopia keniensis overlaps in distribution with X. holtzii , but it differs from that species in the sharply acuminate and nearly glabrous leaf blades, the pedicels short and usually with only one flower per axil, the inner petals strongly geniculate at anthesis, and the sessile monocarps with the seeds arranged in two rows. In seedlings grown side by side, the more pronounced sheen of the X. keniensis leaves is evident (Q. Luke, personal communication).

The species is likely to occur in the Usambara Mountains region of Tanzania, where it may be confused with X. holtzii . As currently known, X. keniensis is very rare, and was given a conservation assessment of Endangered B1ab(iii)+B2ad(iii) by Johnson et al. (2017). We determined it to have the smallest AOO of any African species, 10 km 2.

Figures

Figure 22. Distributions of Xylopia arenaria, X. collina, X. tomentosa, and X. keniensis in southern and eastern Africa. Bolder lines represent country borders, fainter lines lakes and major rivers.

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.