Xylopia lukei D. M. Johnson & Goyder, Kew Bull. 72:11: 3-7. 2017.

Johnson, David M. & Murray, Nancy A., 2018, A revision of Xylopia L. (Annonaceae): the species of Tropical Africa, PhytoKeys 97, pp. 1-252 : 74-75

9. Xylopia lukei D. M. Johnson & Goyder, Kew Bull. 72:11: 3-7. 2017. Fig. 18A-F, H

Type.

MOZAMBIQUE. Cabo Delgado Province, Nangade-Palma, 180 m, Lat 10°54'S, Long 39°54'E, 15 Dec 2003, Q. Luke et al. 10166 (holotype: EA!; isotypes: K! MO! [5795498]) .

Description.

Tree or shrub up to 9 m tall. Twigs light gray to light brown, sparsely appressed pubescent, the hairs 0.2-0.3 mm long, eventually reddish brown, glabrate, with bark exfoliating; nodes occasionally with two axillary branches. Leaf with larger blades 8.2-11.9 cm long, 4.1-5.8 cm wide, subcoriaceous, slightly discolorous, broadly elliptic to ovate, occasionally oblong-elliptic, apex acuminate with an acumen 7-14 mm long, base broadly cuneate to rounded and slightly decurrent on petiole, glabrous adaxially, sparsely appressed-pubescent to glabrous abaxially; midrib plane adaxially, raised abaxially, secondary veins irregularly brochidodromous, 8-15 per side, diverging at 45-80° from the midrib, these and higher-order veins slightly raised on both surfaces; petiole 3.5-10 mm long, flattened to shallowly canaliculate, glabrous to sparsely pubescent. Inflorescences axillary or rarely slightly supra-axillary, 1-5-flowered, appressed-pubescent; peduncles 1-2 per axil, 1.3-2.6 mm long; pedicels 1-3 per peduncle, 4.5-6 mm long, 1.0-1.2 mm thick; bracts 1-3, usually 2, evenly spaced on pedicel, persistent or with lowest caducous, 1.6-2.9 mm long, ovate to semicircular, apex acute to rounded; buds oblong-lanceolate to oblong, apex obtuse. Sepals slightly spreading at anthesis, 1/4-1/2-connate, 2.6-4.7 mm long, 2.6-4.2 mm wide, coriaceous, oblong, the free portion somewhat pentagonal, apex short-acuminate to acute, appressed-pubescent abaxially. Petals apricot-colored to brownish yellow in vivo; outer petals wide-spreading at anthesis, 8.8-15.5 mm long, 2.8-4.2 mm wide at base, 2.5-3.3 mm wide at midpoint, coriaceous or slightly fleshy, lanceolate, apex acute to obtuse, densely pubescent along margins and at the apex but glabrous and verrucose toward the base adaxially, densely appressed-pubescent abaxially; inner petals erect at anthesis, 9.8-12.5 mm long, 2-2.7 mm wide at base, 1.3-2.1 mm wide at midpoint, coriaceous or slightly fleshy, lanceolate, apex acute, base with undifferentiated margin, wrinkled, verrucose, glabrous. Stamens ca. 65; fertile stamens 1.6-2.3 mm long, narrowly oblong, apex of connective ca. 0.1 mm long, truncate, not overhanging anther thecae, glabrous, anthers 6-12-locellate, filament 0.7-1.0 mm long; outer staminodes ca. 1.5 mm long, oblong, apex rounded to truncate; inner staminodes 1.0-1.2 mm long, oblong, apex truncate; staminal cone 1.0-1.2 mm in diameter, ca. 0.8 mm high, concealing only the bases of the ovaries, rim laciniate. Carpels 3-4; ovaries 1.8-2.0 mm long, narrowly oblong, pubescent, stigmas loosely appressed, 1.5-2.0 mm long, lanceolate, apex acute, sparsely pubescent to glabrous. Torus flat or a little bumpy, 1.3-1.7 mm in diameter. Fruit and seeds unknown.

Phenology.

Specimens bearing mature flowers have been gathered in November and December; specimens with flower buds only have been collected in May and September.

Distribution

(Fig. 19 ). Restricted to southeastern Tanzania and northeastern Mozambique, where it occurs in coastal dry forest on reddish orange sands below 200 m.

Additional specimens examined.

TANZANIA. Lindi: Sudi [ca. 10°09'S, 39°58'E], 25 May 1943 (fl buds), Gillman 1465 (EA, K) . MOZAMBIQUE. Cabo Delgado: between Pundanhar and turnoff to Hunters Mozambique hunting camp, towards Nangade , 10° 54' 7"S, 39° 56' 44"E, 169 m, 7 Sept 2009 (fl buds), Burrows et al. 11390 (BNRH, K); Palma District , patch of forest on the coastal plain between the Cabo Delgado peninsula and Quionga, 10°39'03"S, 40°32'59"E, 16 m, 6 Nov 2009 (fl buds), Clarke 97 (K, LMA); N of Palma, on cut line 11 off main road from Palma to Namoto, Way Point: 082 10˚37'27.3"S, 40˚25'05.7"E, ca. 90 m, 6 Dec 2008 (fl buds), Crawford et al. FC323 (K, LMA, P); Nangade to Pundanhar pt427 10.9091°S, 39.9170°E, 168 m, 12 Nov 2009 (fl), Luke & Luke 13760 (EA, K, LMA, MO, P); Quionga to Nachindundo pt437 10.6010°S, 40.6160°E, 60m, 14 Nov 2009 (fl), Luke & Luke 13794 (EA, K, LMA, P); Palma District , Pundanhar to Nangade road. 10°54'29"S, 39°55'12"E., alt. 177 m, 6 Nov 2009 (fl buds), Müller & Clarke 4159 (K, LMA) .

Xylopia lukei is distinctive within section Verdcourtia by virtue of its larger leaf blades, 8.2-11.9 cm long and 4.1-5.8 cm wide, usually distinctly brown-discolored on the abaxial surface, a complex inflorescence consisting of up to five flowers with some pedicels branching from a common peduncle, the pedicels with bracts 2.5-2.9 mm long, and pubescent sepals 3.7-4.7 mm with the free portion of the sepal somewhat pentagonal in shape. In other species of the section, the leaf blades do not exceed 8.7 cm in length and are concolorous, the inflorescences comprise one to two (rarely three) flowers, the bracts of the pedicel only reach 1.4 mm in length and are glabrous, and the sepals do not exceed 2.6 mm in length, are at most sparsely sericeous, and have the free portion broadly triangular in shape.

The coastal dry forests where X. lukei occurs were the subject of a recent floristic analysis by Timberlake et al. (2011), who identified at least 23 other plant species with a similar pattern of endemism. Species mentioned on herbarium labels as associates of X. lukei include Chassalia sp., Erythrococca atrovirens , Pancovia holtzii subsp. holtzii , Pyrostria sp. cf. bibracteata , Rinorea angustifolia subsp. ardisiiflora , Uvaria acuminata , and Warneckea sousae . The forests where the plants occur are currently under threat from road expansion and other land development, and a conservation assessment of Endangered was recently proposed for it ( Johnson et al. 2017; Table 1 ).

Xylopia lukei was informally designated as Xylopia "species A" by Verdcourt (1971b), who did not have adequate material to formally describe it. Additional material now supports Verdcourt’s taxonomy.

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.