Polhillia curtisiae C.H.Stirt. & Muasya

du Preez, B., Dreyer, L. L., Stirton, C. H. & Muasya, A. M., 2021, A monograph of the genus Polhillia (Genisteae: Fabaceae), South African Journal of Botany 138, pp. 156-183 : 175-176

7. Polhillia curtisiae C.H.Stirt. & Muasya ( Fig. 16 ), S Afr. J. Bot. 87: 106 (2013).

Type: South Africa, Western Cape, 3420 (Bredasdorp): Bredasdorp Dist ., Haarwegskloof farm, 12 Oct 2011, Stirton , Muasya & Curtis 13361 ( BOL, holo.!; NBG, iso.!)

Erect, sometimes spreading, sparsely branching shrubs up to 1.0 m tall, sprouting from a woody rootstock. Branches greyish-brown, young branches densely sericeous, becoming glabrescent with age, lenticels prominent. Stipules 2.0 — 4.0 mm long, silvery. Leaflets elliptic-oblanceolate, pale green-grey, villous, conduplicate, flattening partially during wet season, apex acute, base cuneate, terminal leaflet 3.5 — 7.0 X 1.0 — 2.0 mm, lateral leaflets 3.0 — 7.0 X 1.0 — 2.0 mm; leaves subsessile. In fl orescence 1 — 2 flowered terminal cluster, subsessile; pedicel up to 3.0 mm long; bract 1.0 — 1.5 mm long, linear. Flowers yellow, 10.0 — 12.0 mm long. Calyx 4.0 — 5.0 mm long, yellow-green sometimes flushed maroon, villous; tube 3.0 — 3.5 mm long; dorsal teeth broadly triangular, ± 1.5 mm long, fused to ± half of lobe length; ventral teeth narrowly triangular, ± 1.5 mm long, fused for less than two thirds their length, spreading, apex acute-apiculate. Standard (9.0 —) 11.0 — 13.5 mm long; claw linear, 3.0 — 4.5 mm long; lamina broadly ovate, 8.0 — 11.0 X 9.0 — 14.0 mm, apex emarginate, base cordate, back sericeous over entire surface, except along the margin. Wing petals 9.0 — 11.0 mm long, longer than keel; claw 3.0 — 4.0 mm long; lamina oblong-obovate, 7.0 — 9.0 X 3.5 — 5.0 mm, pilose along apical half of midline, apex obtuse, base auriculate; rectangular and lunulate depression with lamellate sculpturing. Keel petals 8.0 — 10.5 mm long; claw 3.0 — 4.0(— 4.8) mm long; lamina obtuse-lunate, 6.0 — 8.0 X 3.5 — 4.0 mm, pilose along fore edge, apex obtuse, base triangular-auriculate. Stamens basifixed anthers 1.1 — 1.2 mm long, carinal anther 0.9 — 1.0 mm long, dorsifixed anthers 0.7 — 0.8 mm long; staminal tube 5.9 — 7.3 mm long, unfused portion remaining equidistant, neatly arranged around style. Pistil 9.0 — 11.0 mm long; ovary 4.8 — 6.8 X 0.9 — 1.0 mm, ovules 9; style usually at about 45 — 60̊ angle, height of curvature 1.2 — 2.9 mm, glabrous except basally. Fruit indehiscent, non-plicate, woody, villous-velutinous, grey-brown, 17.0 — 27.0 X 3.0 — 4.0 mm. Seed ovate-reniform, testa olive-green to black-brown, smooth, 2.0 — 2.5 X 1.8 — 2.3 mm, 1.6 — 2.0 mm thick.

Etymology

The specific epithet “curtisiae ” honours Dr Odette Curtis (CEO, Overberg Renosterveld Conservation Trust) who has studied plants in the Overberg Renosterveld for over a decade, finding numerous new species and playing an integral role in the conservation of Renosterveld vegetation fragments in this region.

Diagnostic characters

Polhillia curtisiae is unlikely to be confused with any other species in its immediate surrounding area in the Overberg. It is morphologically most similar to P. xairuensis , as both species have villous leaflets (versus adpressed sericeous-canescent leaves in other Overberg species); unfused parts of stamens spreading, loosely arranged around style (versus unfused parts of stamens tightly arranged around style in other Overberg species); and style sub-erect, usually angled at between 45 — 60̊ (versus style erect, usually angled at between 70 — 90̊ in other Overberg species). Confusion between this species and P. xairuensis is unlikely as they occur on opposite side of the Breede River. Furthermore, P. curtisiae is an erect shrub of 0.5 — 1.0 m tall (versus taller erect shrub up to 1.8 m tall); wing petals are oblong-obovate (versus strongly obliquely oblong); keel petal apices are obtuse and rounded (versus keel petal apices are acute; and unfused part of the stamens remains neatly arranged around the style (versus unfused parts of stamens loosely spreading and unevenly arranged around the style.

Distribution, ecology and conservation status

Polhillia curtisiae flowers from April to August, with an outlier record from February. It is endemic to the Haarwegskloof and Spitskop area of the southern Overberg district between Swellendam and Bredasdorp ( Fig. 6B ). This species was known only from the type locality in early 2017 but is now known from four scattered locations in this area. The known meta-population of this species has thus now increased from roughly 60 plants to about 500. Populations of this species are fragmented and much of its historical habitat has been lost to agriculture. Remaining sub-populations are in most cases small but are not threatened by further agricultural expansion as they are located on rocky outcrops. Sub-population sizes are, however, of great concern as most of the sites contain less than 50 mature individuals, one of which is limited to a single plant. The type locality of this species is on grey kaolinite clay in the Haarwegskloof Renosterveld Reserve which is part of the Eastern Ruens ^Shale Renosterveld (FRs 13), while the other locations comprised ferricrete and silcrete outcrops where plants grow in Ruens ^Silcrete Renosterveld (FRc 2) Mucina and Rutherford (2006). This species grows either on hill tops or gentle to moderate northerly slopes. The Red Data List status of this species is proposed as Endangered (EN A2c; B 1ab(i,ii,iii,iv,v) + B 2ab(i,ii,iii,iv,v)) following the latest IUCN categories and criteria ( IUCN, 2012).

Additional specimens examined

South Africa. WESTERN CAPE: 3420 (Bredasdorp): About 35 km NE of Bredasdorp, Haarwegskloof 52 (— AD), 16 Aug 2008, Helme & Curtis 5562 (BOL, NBG); Spitskop (East) farm on hill above Eucalypts (— AD), 20 May 2017, B. du Preez 282 (BOL); Spitskop North, koppie east of road (— AD), 9 Jul 2018, B. du Preez 510 (BOL, MO, PRU); Koppie North of Haarwegskloof research centre (— AD), 20 May 2017 B. du Preez 286 (BOL); 6 Aug 2017, B. du Preez 307 (BOL, PRE); 9 Jul 2018, B. du Preez 511 (BOL, NBG); Haarwegskloof farm (— AD), 2 Dec 2011, Stirton & Curtis 13461 (BOL); 12 Oct 2011, Stirton & Curtis 13363 (BOL); 12 Oct 2011, Stirton 13361 (BOL); Muurkraal farm on small koppie (— AD), 9 Sept 2017, B. du Preez 334 (BOL).

Figures

Fig. 16. Composite plate of Polhillia curtisiae. 1 — Flower front view; 2 — Flower side view; 3 — Flower bottom view; 4 — Close-up of leaves and stipules; 5 — Wing petal; 6 — Keel petal; 7 — Androecium;8 — Gynoecium; 9 — Fruit; 10 — Habit.Scale bars:4 mm.Photographs by B.du Preez

Fig. 6. Map showing distribution of Polhillia in the Western Cape Province, South Africa.A — Distribution of extra Overberg species; B — Species within and just outside of the Overberg region. Note expansion of square in A to map in B.