Ypsilopus zimbabweensis Farminhao & P.J.Cribb, 2023

Farminhao, Joao & Cribb, Phillip J., 2023, A new Ypsilopus (Orchidaceae, Angraecinae) from Zimbabwe and notes on the parallel evolution of extreme column exsertion in African angraecoids, Plant Ecology and Evolution 156 (3), pp. 374-382 : 374

Ypsilopus zimbabweensis Farminhao & P.J.Cribb sp. nov.

Figs 1 , 2 , 3 , 4

Type.

ZIMBABWE • Masvingo [Victoria District], ± 3 km from Zimbabwe turn-off on Morgenster road; 12 Jan. 1976; J.S. Ball 1394; holotype: K; isotype: SRGH .

Diagnosis.

Closely allied to Ypsilopus amaniensis (Kraenzl.) D’haijère & Stévart from eastern Africa but differs in having longer leaves (80-130 mm vs 35-115 mm in Y. amaniensis ), inflorescences that greatly exceed the leaves, bearing 10-13 flowers (vs 5-8 in Y. amaniensis ), and having a longer peduncle (45-70 mm vs 10-15 mm) and rachis (120-170 mm vs 50-80 mm).

Description.

Robust, erect or rarely pendent, lithophytic or epiphytic herb, often forming clumps. Roots emerging through the leaf bases opposite the leaves, stout, 8-9 mm in diameter, branching distally, silvery grey. Stems 20-30 or more cm long, 7-9 mm in diameter, covered with sheathing leaf bases. Leaves rigidly coriaceous, 12-16, distichous, twisted just above the basal articulation to lie in one plane, linear-oblong, unequally roundly lobed at the apex, conduplicate at base just above the leaf sheath, 80-130 × 12-19 mm, deep olive-green, articulated to 10-17 mm long leaf sheath. Inflorescences longer than the leaves, arching to pendent, secund in two ranks, 1-several, from leaf sheaths 30-50 mm below the stem apex, 17-23 cm long, 10-13-flowered; peduncle cylindrical, 45-70 mm long, bearing 2-4 sheathing sterile bracts, 5-8 mm long; rachis slenderly cylindrical, slightly zigzag, 12-17 cm long; floral bracts cucullate, ovate, subacute, 6-8 × 4-8 mm. Flowers 22 × 28 mm, showy, white with a buff-tinged spur, the basal flower opening last, diurnally and nocturnally scented of vanilla; pedicel and ovary 22-25 mm long, the ovary scabrid. Sepals and petals reflexed at anthesis. Dorsal sepal linear-elliptic, acuminate, 15-20 × 1.5-2 mm. Lateral sepals similar. Petals narrowly linear-tapering, acuminate, 14-15 × 1-1.5 mm. Lip 3-lobed in the middle, 15-16 × 5-6 mm; side lobes obliquely oblong, truncate, 8-9 × 2-3 mm; midlobe linear-tapering, acuminate, 7-8 mm long; spur pendent, narrowly cylindrical from a narrow mouth, 110-140 mm long. Column 5 mm long, glandular; anther cap giving the tip of the column a hooked appearance; pollinia 2, stipes bifid with linear lobes; viscidium oblong.

Distribution.

Endemic to the Central Watershed of Zimbabwe, in the inselbergs of the southern middleveld margin of the Zimbabwe Craton, west of the Save River, in Masvingo Province (Fig. 1 ).

Habitat.

Epiphyte or lithophyte on inselberg partly-shaded bare rock surfaces; 1000-1300 m.

Phenology.

Flowers in the rainy season, from December to February.

Etymology.

The species is only recorded from Zimbabwe, namely from the area around the Great Zimbabwe National Monument, which gives the country its name.

Additional material (paratypes).

ZIMBABWE • Masvingo [Victoria District], Mt Morgenster; 1000 m (3500 ft); fl. in cult. Harare [Salisbury]; 24 Jan. 1956; R.W. Jackson 56814; K!, SRGH • Masvingo, 16 km NW of Ndanga; 29 Dec. 1976; L.J. Mullin in GHS 25198; SRGH!.

Preliminary IUCN conservation assessment.

The species is given a Red List status of Endangered: EN B1ab(v)+B2ab(v). Ypsilopus zimbabweensis is known from three collections and one observation (https://www.inaturalist.org/observations/143791156) made between 1956 and 2012, representing four occurrences and three locations, including one within the Great Zimbabwe National Monument, a Cultural World Heritage Site. The extent of occurrence (EOO) is 132.1 km2 and the area of occupancy (AOO) is 16 km2. The EOO and AOO fall within the limits of the Endangered (CR) category under subcriteria B1 and B2. Since this species occurs only in three locations and a decline of mature individuals is projected because of illegal collection for the orchid trade, it meets condition b(v) for the EN category.

Notes.

Ypsilopus amaniensis is to be excluded from Flora Zambesiaca, since all regional occurrences correspond to Y. zimbabweensis , namely the recent records illustrated on the Flora of Zimbabwe website ( Hyde et al. 2023). Specimens identified as Angraecum sp. in the inselbergs of Zimbabwe ( Seine et al. 1998) are also possibly ascribable to Y. zimbabweensis . Patricia van de Ruit’s fine watercolour illustration of this species (as Rangaeris amaniensis ) is reproduced here (Fig. 3 ). Iconography produced by the same artist, for the same book, was instrumental to the description of another new orchid from Zimbabwe ( Farminhão and Cribb 2020). The new species is also illustrated here with a line drawing by Andrew Brown (Fig. 2 ) and a photograph in la Croix and la Croix (1997), reproduced here (Fig. 3 ). The novelty has been widely cultivated and misidentified as Rangaeris amaniensis by hobbyists in Zimbabwe, South Africa, Australia, and Europe.

Figures

Figure 1. Possible evidence for reinforcement in the geographical distribution and hypothetical pollinaria attachment sites (on a large sphingid hawkmoth) of two angraecoid clades with divergent column exsertion lengths in tropical Africa. Aerangis gracillima (yellow triangles) is closely allied to A. stelligera (blue triangles), while Ypsilopus amaniensis (blue diamonds) is closely related to Y. schliebenii (yellow diamonds). An extremely elongated Barombia - type column is present in A. gracillima and Y. schliebenii. The three isolated collections of Y. amaniensis in Zimbabwe are here assigned to Ypsilopus zimbabweensis (white diamonds). Photos by Murielle Simo-Droissart (A. gracillima), Bart Wursten (A. stelligera), Guido van Asten (Y. amaniensis), and Russell Hutton (Y. schliebenii).

Figure 2. Ypsilopus zimbabweensis. A. Habit. B. Flower, side view. C, D. Flower, front view. E. Lip margin variability. F. Column, ventral view, with glandular trichomes visible. G. Anther cap, side, dorsal, and ventral views. H. Viscidium and stipes. I. Pollinium (one of two). A (in part), E (in part), F-I drawn from the type collection; A, E (both in part) and I from Jackson 56814; B, C after watercolour by Patricia van de Ruit. All drawn by Andrew Brown.

Figure 3. Watercolour of Ypsilopus zimbabweensis, originally identified as Rangaeris amaniensis, by Patricia van de Ruit, published in Ball (1978: 1394). Reproduced with permission.

Figure 4. Ypsilopus zimbabweensis. A. Plants growing as lithophytes in situ. B. Inflorescence, side view, of plant cultivated in Harare. Photos by Bart Wursten (A) and Isobyl la Croix (B).