Polhillia groenewaldii B.du Preez, 2021

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 : 172

5. Polhillia groenewaldii B.du Preez , sp. nov. ( Fig. 14 )

Type: South Africa, Western Cape, 3320 (Montagu): Bonnievale Region , Bokdam farm, NE of Stormsvlei Pass (— CC), 8 Aug 2018, B. du Preez 522 ( BOL, holo.!; K, MO, NBG, PRU, iso.!)

Erect, rounded shrubs up to 1.2 m tall, sprouting from woody rootstock. Branches grey-brown, rough, densely fissured; lenticels prominent; with terminal burst branching. Stipules 1.5 — 3.0 mm long, green. Lea fl ets narrowly oblanceolate, blue-green, sericeous, partially conduplicate, apex acute, base cuneate, terminal leaflet 4.0 — 8.0 X 1.0 — 2.5 mm, lateral leaflets 4.0 — 7.5 X 1.0 — 2.5 mm; leaves subsessile. In fl orescence 1 — 2 flowered terminal cluster, pseudo-pedunculate, pseudo-peduncles up to 10.0 mm long; pedicel up to 3.0 mm long; bract ± 1.0 mm long, linear-subulate. Flowers yellow, 9.5 — 11.0 mm long. Calyx 3.7 — 4.5 mm long, lime-green, shortly villous; tube 2.5 — 3.5 mm long; dorsal teeth broadly triangular, 1.0 — 1.5 mm long, fused for less than a third of their length, tips acute; ventral teeth triangular, 0.9 — 1.3 mm long, fused for ± two thirds of their length, spreading, tips acute. Standard 9.5 — 11.5 mm long; claw linear, 2.8 — 3.8 mm long; lamina broadly ovate, 7.2 — 8.1 X 8.5 — 10.3 mm, apex emarginate, base cordate; back shortly sericeous only on and around apical half of midline. Wing petals 8.6 — 11.0 mm long, equal to or slightly longer than keel; claw 3.3 — 4.5 mm long; lamina narrowly oblong-lunate, 7.0 — 8.0 X 2.5 — 3.2 mm, glabrous, apex acute-obtuse, base auriculate, triangular and lanceolate depression with lamellate sculpturing. Keel petals 8.8 — 10.0 mm long; claw 3.0 — 4.3 mm long; lamina obliquely-lunate, 6.5 — 7.5 X 3.2 — 3.8 mm, pilose along fore edge, apex obtuse, base auriculate. Stamens basifixed anthers 1.2 — 1.4 mm long, carinal anther 1.0 — 1.1 mm long, dorsifixed anthers 0.55 — 0.65 mm long; staminal tube, 7.0 — 8.6 mm long, unfused portion spreading somewhat, sub-erect, loosely arranged around style. Pistil 8.9 — 10.2 mm long; ovary 6.0 — 7.0 X 0.8 — 1.0 mm, ovules usually 10, sometimes 8 or 11; style usually at about 45 — 60̊(— 80̊) angle, often kinked forward toward apex, height of curvature 1.1 — 2.4 mm, glabrous except basally. Fruit indehiscent, partially plicate, straight or falcate toward apex, sparsely sericeous, dirty-brown drying to cream-brown, 21.0 — 27.0 X 3.0 — 3.2 mm. Seed ovate-reniform; testa olive-green to dark toffee-brown, smooth, 1.9 — 2.4 X 1.7 — 2.2 mm, 1.5 — 1.9 mm thick.

Etymology

The specific epithet “groenewaldii ” honours Mr Jannie Groenewald who first discovered this species and brought it to our attention. This honours the incredible work he has done in increasing our knowledge of new species and also new populations of threatened species in the Overberg region. This is also in recognition of the tremendous help he provided during fieldwork conducted for this study.

Diagnostic characters

Polhillia groenewaldii is morphologically similar to P. obsoleta , but also displays morphological traits typical of Overberg Polhillia species. The presence of pseudo-peduncles with 1 — 2 flowers, leaves that are blue-green in colour and partially conduplicate are similar to P. obsoleta . The strongest difference is that the fruits are elongate and partially plicate, 21.0 — 27.0 X 2.8 — 3.2 mm (versus short and strongly plicate, 16.0 — 23.0 X 3.0 — 4.0 mm); fruit dirty-brown to cream-brown and fibrous (versus fruit russet-brown and woody). Other differences include ovaries with 10, sometimes 8 or 11 ovules (versus ovaries with 12 ovules); style usually at about 45 — 60̊(— 80̊) angles, often kinked forward toward apex, height of curvature 1.1 — 2.4 mm (versus style usually at about a 80̊ angle, height of curvature 2.6 — 2.8 mm); wing petal lamina narrowly oblong-lunate, apex acute-obtuse (versus wing petal lamina obliquely oblong, apex rounded-truncate); bark pale grey-brown, densely fissured and lenticels prominent (versus bark pale green-brown to golden, often relatively smooth and lenticels prominent only on older stems).

Distribution, ecology and conservation status

Polhillia groenewaldii flowers from July to August. It grows on south facing slopes in Breede Shale Renosterveld (FRs 8), which is fairly arid and dominated by Karroid shrubs and succulents such as Tulista pumila (Lam.) G.D. Rowley ( Mucina and Rutherford, 2006) . This species is presently known from a single locality on a road verge between Stormsvlei and Bonnievale ( Fig. 6B ). Only four plants were found at this location and although much of the area is still in a natural state, it is uncertain how much of this may be suitable habitat for this species. This area is generally poorly explored and other sub-populations may still be found. A wide scale search of this area is essential as a population total of four plants renders the long-term survival of this species impossible without ex situ conservation efforts. The population does not appear to be facing any direct threats at present, but the four plants are growing in an old canal up on a road verge. These plants may only be persisting here due to the collection of rainwater in the canal and the remaining area may have become too arid for the species to survive. Climate change may place further strain on the future survival of this species. The Red Data List status of this species is proposed as Critically Endangered (CR B 1ab(i, ii,iii,iv,v)+ B 2ab(i,ii,iii,iv,v); C1+C2a(i,ii); D) following the latest IUCN categories and criteria ( IUCN, 2012).

Figures

Fig. 14. Composite plate of Polhillia groenewaldii. 1 — Flower front view; 2 — Flower side view; 3 — Flower bottom view; 4 — Wing petals; 5 — Keel petals; 6 — Androecium; 7 — Gynoecium; 8 — Fruit; 9 — Close-up of leaves and stipules; 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.