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| Phyllogeiton trachybasis R.G.C.Boon & A.E.van Wyk, in Boon et van Wyk, 2023. |
Abstract
Recently the genus Phyllogeiton was reinstated to accommodate the two currently recognized species of Berchemia, namely P. discolor and P. zeyheri, which are confined to Africa and Madagascar. In the present contribution a new species, Phyllogeiton trachybasis, is described, illustrated, mapped, and compared with the other members of the genus, especially with P. discolor with which it has hitherto been confused. An identification key and illustrations are provided for the three species of Phyllogeiton. The new species has a restricted range and is presently only known for certain from the KwaZulu-Natal part of the Maputaland Centre of Endemism in South Africa. Known trees of P. trachybasis are mostly old and there are no signs of recruitment in nature. Outside conservation areas, the bark of P. trachybasis is heavily utilised for biocultural purposes, most probably a main reason for the apparent demise of the species. A preliminary conservation assessment suggests that P. trachybasis should be classified as Endangered.
Keywords: bark, Berchemia, Berchemia discolor, Maputaland Centre of Endemism, medicine, Rhamnoideae, taxonomy, traditional medicine, muti, muthi, umuthi
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| Phyllogeiton trachybasis (A–E), with fruit of P. discolor (F) and P. zeyheri (G). A. Fruiting branchlet (fruit almost mature). B. Flower. C. Petal. D. Stamen. E–G. Comparison of the fruit (bottom) of the three species of Phyllogeiton, with corresponding enlarged persistent receptacle and fruit stalk (top). Scale bar = 10 mm (A), 1 mm (B–D), or 4 mm (E–G). Drawings based on photographs and liquid-preserved fresh material deposited in Herb. PRU. Artist: Daleen Roodt. |
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| Phyllogeiton trachybasis, bark morphology illustrating variation (A–D) and colour of the wood (E). A. Bark on trunk of old, mature tree. B. Bark on trunk of relatively young tree (sunny habitat). C. Bark on trunk of relatively young tree (shady habitat). D. Exceedingly rough and flaking bark on trunk of mature tree. E. Finely sanded, untreated wood in transverse section; from dead branch ± 130 mm in diameter. Photographs: R.G.C. Boon (A, D), F. du Randt (B, C), & D. Bishop (E). |
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| Phyllogeiton trachybasis, leaf, flower and fruit morphology. A. Branchlet with leaves, the latter fresh green, without a bloom and ca. concolorous. B. Flowers, open and in bud. C. Almost ripe fruit. D. Mainly ripe fallen fruits underneath a tree, some with stone removed or otherwise damaged by wildlife. E. Cleaned stones. Photographs: R.G.C. Boon (A, C, D), G. Nichols (B), & E. Douwes (E). |
Phyllogeiton trachybasis R.G.C.Boon & A.E.van Wyk, sp. nov.
Diagnosis:—Morphologically most similar to Phyllogeiton discolor from which it differs particularly by the following characters: bark on the bole of mature trees almost black, very rough, exfoliating in large pieces; leaves fresh green and without a bloom, ± concolorous, apex acuminate; petals spreading to somewhat ascending at anthesis; fruit oblong-ellipsoid, up to 25 × 19 mm, exocarp often indistinctly longitudinally ribbed, bright orange-yellow; disc-shaped receptacle at point of fruit stalk’s attachment to base of fruit plane.
Etymology:—The specific epithet “trachybasis” is derived from the Greek τραχυς, trachys, rough or shaggy, and βασις, basis, base or pedestal, referring to the bark towards the base of the trunk in old trees that becomes very thick, rough and flaking in large pieces (Figs 1 & 2A–D). The epithet is used here as a noun in apposition: “the shaggy base” and therefore does not necessarily agree in gender with the genus name.
Richard G.C. Boon and Abraham E. van Wyk. 2023. A New Species of Phyllogeiton (Rhamnaceae: Rhamneae) from Maputaland, South Africa. Phytotaxa. 585(3); 193–209. DOI: 10.11646/phytotaxa.585.3.2
