Psoralea nubicola C. H. Stirt. & Muasya, 2024

Stirton, Charles H., Bello, Abubakar & Muasya, A. Muthama, 2024, Ten new species and notes on the genus Psoralea L. (Psoraleeae, Fabaceae) from South Africa, Plant Ecology and Evolution 157 (3), pp. 291-312 : 291-312

6. Psoralea nubicola C. H. Stirt. & Muasya sp. nov.

Figs 2 , 8

Psoralea sp. 17 (“ Psoralea nubicola C. H. Stirt. ms. ”, nom. nud.), Stirton and Schutte (2012: 574)

Type.

SOUTH AFRICA – Western Cape Province: 3320 (Montagu) • above Grootvadersbosch, highest point of Lemoenshoek Peak ; 33 ° 55 ’ 0.68 ” S, 20 ° 52 ’ 30.94 ” E; 6 Dec. 1981; 1366 m a. s. l.; Stirton, Rourke & Esterhuysen 10212; holotype: NU [ NU- 0015573-2 ]; isotypes: BOL, BR, J, K, MO, NBG, NH, NU [ NU 0015573 -1 , NU 0015573 -3 , NU 0086848 ], P, PRE, SCHG .

Diagnosis.

Species similar to Psoralea forbesiae C. H. Stirt., A. Bello & Muasya which occurs in the Swartberg Mountains but differs in its low sprawling habit ( P. forbesiae densely branched shrubs up to 2.5 m tall with most parts covered in small crater-like glands; mature plants can be hemi-spherical); leaves bluish-green, narrowly obovate, 7–8 × 2–3 mm, terminal leaflet longer and wider than the 5–7 × 2 mm, elliptic to narrowly elliptic laterals ( P. forbesiae leaves yellowish green, linear-oblong, 13–22 × 0.5–0.6 mm, terminal leaflets longer and wider than 12–20 mm long, 2–3 mm laterals); flowers exceed leaves ( P. forbesiae flowers about same length as leaves); flower buds held vertically to the sprawling shoots ( P. forbesiae flowers held laterally to vertical shoots); standard petal purple to violet-mauve with darker veins ( P. forbesiae standard petal white or mauve fading towards margins, with a purple vertical flash tapering to the apex and some basal veins purplish, apex greenish on front and back).

Description.

Low sprawling, resprouting shrub up to 80 cm tall and 300 cm wide, highly resinous, strong smelling. Stems profusely and densely branched, splayed, stacked in layers, intertwined, glabrous, densely warty. Leaves pinnately 3 - foliolate, rarely 4 - foliolate, petiolate, 9–10 mm long, stipulate, densely glandular. Leaflets elliptic to narrowly obovate (terminal only), subequal, somewhat conduplicate, fleshy, bluish-green, glabrous, densely glandular, glands fewer and larger below than above, drying black; terminal leaflet longest, 7–8 × 2–3 mm, laterals 5–7 × 2 mm, symmetrical; petiole 4–5 mm long, rachis 2 mm long. Stipules 2–3 mm long, paired, fused at base to petiole, triangular, glaucous, persistent, patent, margins dimpled, glabrous, glands prominent. Inflorescences 1 - flowered, borne sequentially (trap-line) in most nodes of short seasonal shoots; peduncle present, 15–26 mm long, twice longer than flower; pedicel 2 mm long. Flowers 10 mm long, purple to violet-mauve and white; buds purplish; cupulum 3–4 - fid, teeth situated near apex of the peduncle, 3–4 mm long, carinal tooth largest, glabrous, pubescent inside teeth, hairs black and white, few hairs along the teeth. Calyx 7 mm long, lobes equal, teeth triangular to lanceolate, vexillar pair somewhat falcate, and somewhat fused above tube; glabrous outside, finely black-haired on inside of teeth; tube 4 mm long, distinctly ribbed, glandular. Standard petals 8 × 9 mm long; claw 2 mm long; very broadly ovate, dark mauve to violet-mauve, veins darker, appendages present, parallel situated above the auricles, apex emarginate, reflexed 90 ° degrees; nectar patch present, comprised of a white M-shaped patch above the appendages and with a central vertical purple flash. Wing petals 7 × 3 mm; claw 3 mm long; white, free from and longer than keel petals, cultrate, strongly folded along top third, apex rounded; base of blade auriculate on upper basal margin, sculpturing present, upper basal comprising 2–3 transcostal lamellae in 3 rows; tips of blade flared outwards but almost cucullate. Keel petals 9 × 3 mm; claw 3 mm long; white with purple patch on inner faces near the tip, not fused to the wing petals. Androecium 9 mm long; tenth stamen free from the adaxially split sheath, fenestrate at base. Pistil 9 mm long, gynophore present, ovary 1 mm long, glabrous except for club-shaped glands towards apex of ovary; height of curvature 3.5 mm, thickened at point of flexure, stigma capitate. Fruits and seeds unknown.

Distribution and habitat.

Psoralea nubicola is a high montane endemic found in rich peaty soils within rocky outcrops in mountain fynbos between 1500 and 1800 m a. s. l. in the North Langeberg Sandstone Fynbos (FFs 15) vegetation type (Fig. 2 ) and occurs in a few massed colonies on the highest points of the uppermost peaks of the Langeberg mountains ( Mucina and Rutherford 2006). No other Psoralea in the Cape is situated as high as this species. These localities are regularly covered in mist or dense clouds.

Phenology and ecology.

Flowering takes place between August and November. Something very akin to this species occurs in the uppermost parts of the Swartberg Mountains and may belong to this species but only a few isolated plants have been found near the summit and although similar in many features the plants appear to be part of the hybrid swarm reported from the Swartberg Pass ( Bello et al. 2018) so are difficult to assess. Further field investigation is needed of the Swartberg plants.

Etymology.

The specific epithet nubicola (Latin ‘ nubis’ = cloud and ‘ cola’ = dweller) refers to its high mountain habitat.

Preliminary IUCN conservation assessment.

The known isolated distribution of this species lies within a protected area. It has no perceived threats. A drying climate may be a long-term threat as it probably relies on precipitation from mist for its moisture requirements. It dominates the local vegetation. It is currently assessed as of Least Concern: LC ( IUCN 2012).

Additional material examined.

SOUTH AFRICA – Western Cape Province: 3320 (Montagu) • above Grootvadersbosch, Lemoenshoek Peak (- DD); 2 Jul. 1981; Rourke 1760; NBG • Grootberg (- DD); 14 Dec. 2007; Knox 5205; BOL • ibid.; Nov. 1927; Thorne s. n.; NBG [ SAM 44530 ] .

Figures

Figure 2. Known distribution of the ten described Psoralea species. Map by Abubakar Bello.

Figure 8. Psoralea nubicola. A. Sprawling habit and rocky habitat with Charles Stirton (left) and John Rourke (right). B. Layered prostrate branching habit with older yellowish branches visible. C. Flower buds. D. Side view of a flower. E. Frontal view of flower. Photographs: A by Elsie Esterhuysen; B – E by Charles Stirton.