Polhillia xairuensis B. du Preez 2021, sp. nov.
Creators: name: du Preez, B.
name: Dreyer, L. L.
name: Stirton, C. H.
name: Muasya, A. M.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Fabales
Fabaceae
Polhillia
Polhillia xairuensis

description: 8. Polhillia xairuensis B.du Preez, sp. nov. (Fig. 17)
Type: South Africa, Western Cape, 3420 (Bredasdorp): Suurbraak Region, Voorstekop farm (— BC), 11 Aug 2017, B. du Preez 315 (BOL, holo.!; K, NBG, PRU, iso.!)
Erect, rounded shrubs up to 1.0 — 1.5(— 1.8) m tall, often wider than tall, sprouting from a woody rootstock. Branches greyish-brown, glabrescent, terminal burst branching present, often forming a closed, dense, umbrella-like canopy; lenticels prominent on old stems. Stipules 1.5 — 2.5 mm long, silvery. Lea fl ets lanceolate to narrowly-oblong grey-green, villous, conduplicate, flattening partially during the wet season, apex acute-apiculate, base cuneate, terminal leaflet 3.0 — 5.5 X 1.0 — 2.0 mm, lateral leaflets 2.5 — 5.0 X 1.0 — 2.0 mm; leaves subsessile. In fl orescence 1 — 2 flowered terminal cluster, subsessile; pedicel up to 3.5 mm long; bract 1.0 — 1.5 mm long, linear. Flowers yellow, 10.0 — 11.5 mm long. Calyx 3.5 — 5.0 mm long, green, often flushed maroon, villous; tube 2.5 — 3.5 mm long; dorsal teeth broadly triangular, 1.0 — 1.5 mm long, fused for more than two-thirds their length, tips acute; ventral teeth narrowly-triangular, 1.0 — 1.5 mm long, fused for two-thirds their length to almost entirely fused, spreading, apex variable, acute-rounded. Standard 11.0 — 12.5 mm long; claw linear, 4.0 — 4.5 mm long; lamina broadly ovate, 7.0 — 8.5 X 9.5 — 11.0 mm, apex emarginate, base cordate; back sericeous except along margin. Wing petals 9.0 — 11.0 mm long, equal to or slightly longer than keel; claw 3.5 — 4 mm long; lamina obliquely oblong, 8.0 — 9.0 X 3.5 — 4.0 mm, glabrous to rarely sparsely pubescent along apical half of midline, apex rounded, base broadly auriculate, basal margin revolute, long elliptical depression and lamellate sculpturing. Keel petals 8.5 — 10.0 mm long; claw 4.0 — 4.5 mm long; lamina lunate, 7.5 — 8.0 X 3.0 — 4.0 mm, pilose along fore edge, apex acute, base auriculate. Stamens basifixed anthers 1.3 — 1.4 mm long, carinal anther 1.2 mm long, dorsifixed anthers 0.9 — 1.0 mm long; staminal tube 7.4 — 8.2 mm long, unfused portion spreading, loosely arranged around the style. Pistil 10.0 — 11.3 mm long; ovary 6.2 — 8.2 X 0.9 — 1.2 mm, ovules 9; style usually at about 45̊ angle, height of curvature 1.1 — 1.9 mm, glabrous except basally. Fruit indehiscent, non-plicate, straight to slightly falcate, fibrous, sericeous, olive-green at maturity, 21.0 — 28.0 X 3.0 — 3.5 mm. Seed ovate-reniform; testa dark black-brown, smooth, 2.2 — 3.0 X 1.9 — 2.4 mm, 1.4 — 1.7 mm thick.
Etymology
The specific epithet is derived from the Hessequa Khoi name for the Suurbraak area, namely “!Xairu” which means ‘Beauty’ or ‘A place called Paradise’, referring to the beautiful nature of the area (Fourie, 2013). Pronunciation of the epithet can be with or without a click. Although much of the area has now been transformed for agriculture, the Langeberg Mountains above the town of Suurbraak remain scenic and lowland vegetation fragments hold beautiful floral gems such as this Polhillia species.
Diagnostic characters
Polhillia xairuensis was previously thought to be a form of P. pallens, but is instead morphologically most similar to P. curtisiae, which occurs further west. It may be confused with P. pallens, as there are populations in close proximity on the eastern side of the Breede River. It can be distinguished from P. pallens by its villous, lanceolate to narrowly oblong leaflets (versus adpressed sericeous-canescent, elliptic to broadly-oblong leaflets); stamens loosely spreading around style, style at ± 45̊ angle (versus stamens tightly arranged around style, style at 70 — 90̊ angle); plants with terminal burst branching often forming dense closed canopies (versus plants with scattered branching and no closed canopy); wing petals completely glabrous or very sparsely pubescent (versus wings clearly pubescent along midline); keel petal apex acute (versus keel petal apex obtuse-rounded); lower three calyx teeth almost completely fused with rounded-obtuse tips (versus lower three calyx teeth fused for less than half their length with acute tips). Confusion between this species and P. curtisiae is unlikely, as they occur on opposite sides of the Breede River and can be distinguished by plants height up to 1.8 m tall (versus shrub less than 1.0 m tall); unfused part of stamens loosely spreading unevenly around style (versus unfused part of stamens spreading neatly arranged around style); wing petals strongly obliquely oblong (versus wing petals oblong-obovate); keel petal apex acute (versus keel petal apex rounded).
Distribution, ecology and conservation status
Polhillia xairuensis flowers from July to September. It is restricted to a few sites in Eastern Ruens ^Silcrete Renosterveld (FRc 2) in the Suurbraak area (Fig. 6B) between Swellendam and Heidelberg (Mucina and Rutherford, 2006). It grows in loamy soils, usually in gullies or on gentle slopes. Much of this species’ historical habitat has been transformed for agriculture, but roughly 1000 plants persist on small vegetation fragments that are unlikely to be ploughed in future. The Red Data List status of this species is proposed as Endangered (EN A2c; B 1ab(iii,v)+ B 2ab(iii,v)) following the latest IUCN categories and criteria (IUCN, 2012).
Additional specimens
South Africa. WESTERN CAPE: 3420 (Bredasdorp): Swellendam, 15 km SE of Buffeljagsrivier on Hartebeesterivier 278 (— BA), 27 Sept 2001, Helme 2282 (NBG); Niekerkshek, 20 km east of Swellendam (— BA), 19 Jul 2003, Kloppers s.n. sub 195427 (NBG); Voorstekop farm, between Heidelberg and Swellendam (— BA), 25 Nov 2011, Muasya, Stirton & Curtis 6265 (BOL); Voorstekop farm, near guest lodge (— BA), 10 Sept 2017, B. du Preez 335 (BOL); Suurbraak commonage, Alan Jafta’ s farm (— BA), 10 Sept 2017, B. du Preez 337 (BOL, MO, PRE); 25 Nov 2011; Stirton & Curtis 13531 (BOL); Zoutkloof farm, south of Voorstekop (— BA), 16 Oct 2017, B. du Preez 392 (BOL); Oudekraalskop (— BA); 19 Jun 2012; Curtis 111 (BOL); Suurbraak (— BA), 10 Sept 2011, Curtis 14 (BOL).
description: Published as part of du Preez, B., Dreyer, L. L., Stirton, C. H. & Muasya, A. M., 2021, A monograph of the genus Polhillia (Genisteae: Fabaceae), pp. 156-183 in South African Journal of Botany 138 on pages 176-177, DOI: 10.1016/j.sajb.2020.12.022, http://zenodo.org/record/10496862