Xylopia tanganyikensis D.M.Johnson

First published in Kew Bull. 72(1)-11: 9 (2017)
This species is accepted
The native range of this species is W. Tanzania. It is a tree and grows primarily in the wet tropical biome.

Descriptions

Johnson DM et al. 2017. New species of Xylopia (Annonaceae) from East Africa. Kew Bulletin 72:11. DOI 10.1007/S12225-017-9681-X

Type
Type: Tanzania, Kigoma Region: T4, Kigoma Distr., Mahali Mts, 800 – 1500 m, Nishida 57 (holotype K!; isotype EA!).
Morphology General Habit
Tree at least 7 m tall or perhaps taller [“high tree” fide Uehara 580]
Morphology Twigs
Twigs reddish brown to blackish brown, sparsely and finely pubescent, lenticellate, at length grey to grey-brown and sparsely pubescent to glabrate; nodes occasionally with two axillary branches
Morphology Leaves Leaf lamina
Lamina of larger leaves 6.4 – 9.0 cm long, 1.8 – 2.6 cm wide, chartaceous, usually discolourous (grey above, yellow-olive to tan and paler below), lanceolate to elliptic, apex acute, acuminate, obtuse, or retuse, and sometimes 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 10 – 17 per side, diverging at c. 60° from the midrib, brochidodromous, these and higher-order veins indistinct to slightly raised on both surfaces; petiole 2 – 3.5 mm long, shallowly canaliculate, pubescent
Morphology Reproductive morphology Inflorescences
Inflorescences axillary, 1-flowered, sparsely pubescent; pedicels 2.8 – 3 mm long, bracts 2 – 3, caducous, uppermost bract c. 1.7 mm long, semicircular, apex rounded; buds linear, falcate, apex acute
Morphology Reproductive morphology Flowers Calyx
Sepals ¼-connate, 2 – 3 mm long, 2.8 – 3.2 mm wide, coriaceous, ovate to broadly ovate, apex acute or apiculate, densely sericeous abaxially
Morphology Reproductive morphology Flowers Corolla
Outer petals 28 – 38 mm long, 3.8 – 3.9 mm wide at base, 1.5 mm wide at midpoint, coriaceous, linear, longitudinally concave adaxially, longitudinally ridged abaxially, acute at the apex, brown-pubescent on both surfaces; inner petals 27 – 31 mm long, 2.9 mm wide at base, 0.9 – 1.0 mm wide at midpoint, coriaceous, linear, longitudinally ridged on both surfaces, concave at the base adaxially, acute at the apex, greyish silver-pubescent on both surfaces
Morphology Reproductive morphology Flowers Androecium Stamens
Stamens c. 170, 1.3 – 2.7 mm long, narrowly oblong; apex of anther connective 0.1 – 0.2 mm long, forming a flat cap over the tops of the anther thecae, finely papillate; filament 0.4 – 0.6 mm long, forming ¼ – 1=3 of stamen length; both outer and inner staminodes present, the inner ones shorter; staminal cone c. 1 mm high, 2.1 mm in diam., irregularly laciniate around the rim
Morphology Reproductive morphology Flowers Gynoecium Carpels
Carpels c. 11; ovaries c. 1.2 mm long, oblong, pubescent; stigmas c. 2.5 mm long, linear with a tuft of hairs at the apex; ovules 6 – 9, interdigitated to form a single row
Morphology Reproductive morphology Flowers
Torus c. 2.7 mm in diam., flat
Morphology Reproductive morphology Flowers Pedicel
Pedicel of fruit 5 – 16 mm long, 1.3 – 6 mm thick, sparsely pubescent to glabrate; torus of fruit 9 – 14 mm in diam., 8 mm high, fist-shaped
Morphology Reproductive morphology Fruits
Monocarps with endocarp becoming red when ripe in vivo, up to 9 per fruit, 3.0 – 5.4 cm long, 1.6 – 2.0 cm wide, 0.8 – 1.6 cm thick, obovoid to oblong-obovoid, apex rounded, base sessile or contracted into a stipe 2 – 10 mm long and 3.5 – 6 mm thick; pericarp 0.5 – 0.7 mm thick, finely warty, glabrous
Morphology Reproductive morphology Seeds
Seeds arranged in a single or irregular double row, oriented obliquely to long axis of monocarp, 3 – 7 per monocarp, 9.4 – 14.0 mm long, 6.9 – 9.2 mm wide, 6.2 – 8.4 mm thick, ellipsoid to oblong, irregularly elliptic to cuneiform in cross section, smooth, rounded at chalazal end, truncate at micropylar end, raphe/antiraphe not evident on surface; micropylar scar 5 – 5.5 mm long, 3 – 4 mm wide, ovoid, flat; aril absent
Distribution
Africa: western Tanzania, on E side of Lake Tanganyika.
Ecology
Evergreen forest with Congolian affinities, at elevations of 800 – 1600 m.
Conservation
Apart from Abeid et al. 1028, all the known specimens are from the Mahali Mountains and can be assumed to fall within the National Park boundaries. If the cell size is taken as 3.17 km2 the AOO is 40 km2 assuming that the two Nishida collections are taken as being from the same locality. The polygon formed between the NP boundary and the Abeid specimen gives an EOO of approximately 2500 km2. If all specimens were from within the Park there would be no threat to the species as it is understood that the area is well managed (LC (CD)), however the one known population outside the Park is at risk. The area is settled by refugees and under increasing pressure for conversion to farms and for timber harvesting for firewood and construction material (David Moyer, pers. comm.). The IUCN conservation status thus is assessed as EN B1ab(iii) + B2ab(iii).
Phenology
Flowering specimens have been collected in March and April, specimens with fruit collected in April and July.
Note
This species is named after Lake Tanganyika, given the proximity of all its localities to the lake. This species most closely resembles Xylopia elliotii Engl. & Diels of western Africa in its discolourous leaves and oblong to obovoid monocarps with rounded apices, but the latter species is a smaller tree (up to 10, rarely 18 m in height) of gallery forest with longer flower pedicels (3 – 6 mm long) and monocarps only reaching 3.8 cm in length, with two distinct rows of seeds. X. tanganyikensis also superficially resembles X. cupularis Mildbr. of central Africa, but lacks the golden-sericeous abaxial leaf surface, the longer pedicels (4 – 12 mm long) and the many (up to 18) long-stipitate monocarps of that species. Xylopia tanganyikensis may be most readily distinguished from X. parviflora sensu Verdcourt by the discolorous leaves, the more variable shape of the leaf apex (acuminate to retuse), the longer petals and the larger monocarps and seeds. X. odoratissima, with which it possibly overlaps in distribution, is a smaller tree of miombo woodland with broader and more pubescent leaves. X. arenaria Engl., which also has leaves that are appressed-pubescent on the abaxial surface, is a shrubby plant of coastal forests with much smaller flowers and fruits. According to a note by J. B. Gillett attached to the type sheet, “The fruits previously picked up from the ground were with no. 51, otherwise identical with 57 and same inadequate data. Coll. T. Nishida 57 (+51).” We thus understand that the flower shoots mounted on the sheet and the dehisced monocarps in the packet represent two different gatherings and two different collection numbers. The sheet at EA has this same mixture. To avoid future confusion, the type is explicitly designated to be the flowering shoots, and the collection number is understood to be Nishida 57; the collection number Nishida 51 is understood to apply to the fallen fruits only. This species is unique in the combination of narrow discolourous leaves that are appressed pubescent abaxially, short-pedicellate flowers with narrow petals up to 38 mm long, and sessile monocarps that are widest at or beyond the middle and rounded at the apex.
[KBu]

IUCN Red List of Threatened Species https://www.iucnredlist.org/species/137024987/137048397

Conservation
EN - endangered
[IUCN]

Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592

Conservation
Predicted extinction risk: threatened. Confidence: confident
[AERP]

Sources

  • Angiosperm Extinction Risk Predictions v1

    • Angiosperm Threat Predictions
    • http://creativecommons.org/licenses/by/4.0
  • Herbarium Catalogue Specimens

    • 'The Herbarium Catalogue, Royal Botanic Gardens, Kew. Published on the Internet http://www.kew.org/herbcat [accessed on Day Month Year]'. Please enter the date on which you consulted the system.
    • Digital Image © Board of Trustees, RBG Kew http://creativecommons.org/licenses/by/3.0/
  • IUCN Categories

    • IUCN Red List of Threatened Species
    • http://creativecommons.org/licenses/by-nc-sa/3.0
  • Kew Backbone Distributions

    • The International Plant Names Index and World Checklist of Vascular Plants 2025. Published on the Internet at http://www.ipni.org and https://powo.science.kew.org/
    • © Copyright 2023 World Checklist of Vascular Plants. http://creativecommons.org/licenses/by/3.0
  • Kew Bulletin

    • Kew Bulletin
    • http://creativecommons.org/licenses/by-nc-sa/3.0
  • Kew Names and Taxonomic Backbone

    • The International Plant Names Index and World Checklist of Vascular Plants 2025. Published on the Internet at http://www.ipni.org and https://powo.science.kew.org/
    • © Copyright 2023 International Plant Names Index and World Checklist of Vascular Plants. http://creativecommons.org/licenses/by/3.0