Aspalathus praetermissa C.H.Stirt., Du Preez & Helme, 2024

Stirton, Charles H., Preez, Brian Du, Helme, Nick & Muasya, A. Muthama, 2024, A new species of Aspalathus (Fabaceae, Crotalarieae) from the Cape Floristic Region, South Africa, Phytotaxa 665 (1), pp. 69-74 : 70-72

Aspalathus praetermissa C.H.Stirt., Du Preez & Helme , sp. nov. ( Fig. 1 )

Diagnosis: —Morphologically similar to Aspalathus quinquefolia subsp. virgata ( Thunberg 1800: 126) Dahlgren (1960: 240) . Both taxa belong to Dahlgren’s (1988) Group 1: Sericeae, sharing features of general habit being erect, single-stemmed shrubs up to 2 m with terminal spicate inflorescences, hairy petals; bi-ovulate ovaries, 1-seeded and obliquely ovate fruits. Aspalathus praetermissa differs in having mature branchlets characterised by prominent persistent swollen leaf bases becoming woody with age (vs scarcely so); leaves borne in tightly packed fascicles of up to 9 leaflets, obovate to ovate, silvery sericeous or almost woolly densely pubescent on seasonal shoots (vs leaves trifoliolate, oblong or narrowly elliptic, grey or silvery green, pubescent on young leaves becoming glabrescent), flowers pale yellow and 5.5–6.0 mm long (vs flowers bright yellow and 7–10 mm long), flowers opening gradually along inflorescence (vs flowering synchronously), wing petals hairy along entire ventral half and not flared towards apex (vs hairy only basally on ventral half to entirely glabrous and flared away towards the apex).

Type: — SOUTH AFRICA. Western Cape: Vensterklip farm, north of Verlorenvlei, Sandveld District , 21 November 2018, B. du Preez 609 (holotype BOL!; isotypes K!, NBG!, PRE!) .

Plant a tall compact shrub to 2 m tall, single-stemmed but branching from near base, reseeder. Older stems with greybrown, rough and longitudinally fissured bark. Mature branchlets characterised by prominent persistent swollen hairy leaf bases. Seasonal shoots silvery, densely woolly. Leaves tightly packed and overlapping in fascicles of up to 9 leaflets, but trifoliolate on young flowering branches. Leaflets 2.0–3.5 × 1–2 mm, flat, obovate-ovate, apex acute to obtuse, weak, spreading; leaf bases long sericeous to woolly, persistent, becoming raised and woody with age. Inflorescences a dense, imbricate terminal spike borne on seasonal branches whereas short side shoots are usually subtended by single leaf. Flowers 5.5–6.0 mm long, pale-yellow; subsessile; bract 4 × 2 mm long, spathulate, apex attenuate, densely sericeous; bracteoles 3.5–4.0 × 0.5–1.0 mm, narrowly lanceolate. Calyx 3.5–4.0 mm long, campanulate, sericeous externally, silvery green; tube 2.0– 2.5 mm long; lobes narrowly triangular, tips acute, dorsal and lateral lobes 1.5 mm long. Standard blade 4.5–5.0 × 3.0– 3.5 mm, pale yellow with golden nectar guide that turns dark brown after anthesis, exceeding leaves, sides curved backwards, ovate, apex rounded to emarginate, back of standard entirely densely sericeous, midrib on reverse not visible; claw 1.5–2.0 mm long, linear. Wing petals 4.0– 4.5 mm long, blades 2.7–2.9 × 1.5–1.7 mm, elliptical-rectangular, not flared away from keel, apex obtuse, base truncate, slightly longer than keel, concave above midline, clasping keel, hairy on lower half of blade; petal sculpturing lamellate, 15–20 rows along basal to mid dorsal portion of blade; claw 1.7–2.0 mm long. Keel petals 3.6–3.9 mm long, well-exposed and almost woolly, blades 2.5–2.6 × 1.3–1.5 mm, obovate, fused, long sericeous, apex rounded, base auriculate, pocketed basally, claw 1.5–1.8 mm long. Androecium 3.4–3.6 mm long, filaments fused into a staminal tube, slit dorsally, free at tips, erect; anthers 10, 6 shorter basifixed, 0.3 mm long, and 4 longer dorsifixed (arranged: LSLSSSLSLS), 0.4 mm long; versatile. Pistil 5.4–5.7 mm long, subsessile; ovary 2 mm long, 0.9 mm high, lanceolate, sericeous, ovules 2; style straight to upcurved, robust, sericeous only along lower third; stigma regular, capitate. Fruits obliquely-ovate, 3.4 × 1.9 mm long, colour pale green when young, mature fruits not seen, sericeous. Seed not seen.

Etymology:— The specific epithet praetermissa is derived from the Latin word praetermissus, meaning overlooked and alludes to how this distinctive species was only discovered fairly recently on private farmland during ecological surveys.

Phenology:— Flowering has been recorded over an extended period, from February to May and from August to February, and plants are most likely to be in flower from September to May.

Diagnostic characters:— Aspalathus praetermissa is a distinctive species of Dahlgren’s (1988) Group 1: Sericeae. Species in this group are characterised as shrubs or shrublets of variable size bearing flat weak leaves clothed in sericeous to puberulous pubescence, rarely glabrous or glabrescent. The mostly yellow flowers are borne singularly or in few to many-flowered racemose to spicate and capitate inflorescences, nectar guides in older flowers mostly turning orange. Bracts and bracteoles are always present, well-developed, simple, and flat. Pedicels are short to obsolete. All petals are hairy to some extent ( Dahlgren 1988). Aspalathus praetermissa is most similar to Aspalathus quinquefolia subsp. virgata , and although these taxa occur sympatrically, the latter has a much wider distribution. Aspalathus praetermissa differs in having short shoots bearing silvery almost woolly densely-packed flat leaves (vs leaves singular on short shoots, pubescent to glabrescent). Flowers of the new species are 5.5–6.0 mm long and pale yellow (vs 7–10 mm long and bright yellow). The wing petals are pubescent on the entire ventral half and not flared towards the apex (vs pubescent only basally on ventral half to completely glabrous and flared towards the apex).

Distribution and habitat:— Aspalathus praetermissa is a restricted local endemic occurring on the coastal plain east of Elandsbaai in the Western Cape Province of South Africa ( Fig. 2).

The known distribution lies between Elandsbaai in the west, Paleisheuwel in the east, Leipoldtville in the north, and Redelinghuys in the south, an area of about 150 km 2. It was collected for the first time in 2009 by Nick Helme, photographed by Benjamin Walton in 2017, and collected and photographed again at various localities in 2018 by Nick Helme. It grows in deep, acid, low nutrient sands, entirely within the vegetation type described by Rebelo et al. (2006) as Leipoldtville Sand Fynbos (FFd2). It occurs at an elevation of 50–200 m above sea level, and does not occur on steep or rocky slopes. This species is a fire weed (flowering best after fire, and being significantly more abundant in younger veld), and unusually for an Aspalathus is quite persistent (in low numbers) in veld not burnt for up to 30 years.

Conservation status:— Aspalathus praetermissa faces a noticeably clear threat to its survival from rapid conversion of the natural veld into cropland. The scale of the threat is easily visible from satellite photography taken in 2019 ( Fig. 3 ). About 70% of the suitable habitat within its known range has been lost to potato and rooibos tea cultivation, mostly within the last 30 years, and the loss is ongoing.

The new species does not occur within any nationally protected areas but does occur in a few existing and proposed Contract Nature Reserves, which are privately owned. The population is already heavily fragmented by cultivation, and population size is difficult to estimate, partly because it is significantly less common in veld that has not burned for more than 15 years. As high value crops fragment the landscape, landowners are reluctant to burn the veld and this could result in a failure to recruit in these areas, and some individuals dying from senescence. Based on available data, an Extent of Occurrence (EOO) of 49 km 2 and Area of Occupancy (AOO) of 16 km 2 are inferred for this species. These values meet the criteria necessary to be listed as a threatened species based on the IUCN Criteria and Categories ( IUCN 2012). This area is fairly poorly explored by botanists, and more sub-populations may exist in small vegetation fragments, but it is likely that most of the historical distribution range of the species has been lost to crop cultivation. Due to a lack of historical data for this species, population size reduction under criterion A cannot be accurately inferred, but it is likely to be in the range of 70–80 percent. Based on the severely fragmented nature of the area between known sub-populations, lack of fire preventing seedling recruitment, and ongoing habitat loss, we determine that it be Red listed as Critically Endangered (CR: B1ab(i,ii,iii,iv,v)).

Additional specimens examined:— SOUTH AFRICA. Western Cape: Sandberg farm, Donkieskraal Game Lodge , 250 m elev, 07 October 2023, L.K. Madika, S. Kritzinger-Klopper & A. Ndaba LK93 ( BOL) ; Bonteheuwel Farm , farm, 173 m elev, 28 May 2016, B. Walton s.n. ( BOL) ; Droogerivier farm, 21km NE Redelinghuys, 171m elev, 11 September 2018, N. Helme 9315 ( NBG, BOL) ; Sebulon , 15km E Elandsbaai, first posted on iSpot by B. Walton, 19 February 2018, N. Helme 9310 ( NBG), https://www.inaturalist.org/observations/9931220 .

iNaturalist and iSpot observations:— SOUTH AFRICA. Western Cape: NW of Verlorenvlei, 21 November 2018, Riaan van der Walt, observation only, https://www.inaturalist.org/observations/10008666; Vensterklip farm, 21 November 2018, Petra Broddle, observation only, https://www.inaturalist.org/observations/18774026; Vensterklip farm, 21 November 2018, Gigi Laidler, observation only, https://www.inaturalist.org/observations/18557636, Farm Bonteheuwel No. 1, 268 m elev, 7 February 2017, Benjamin Walton, observation only, Aspalathus sp. | Observation | Southern Africa | iSpot (ispotnature.org); Kruisfontein, Redelinghuys, 9 September 2009, Nick Helme, observation only, https://www.inaturalist.org/observations/13075649.

Figures

FIGURE 1. Aspalathus praetermissa. A. Flower front view. B. Flower side view. C. Flower basal view. D. Wing petals, upper one outer surface, lower one inner surface. E. Keel petals, upper one outer surface, lower one inner surface. F. Androecium. G. Pistil. H. Unripe pod. I. Leaf fascicles. J. Inflorescences on seasonal shoots. K. Habit of old plant and habitat. Scale bars: 2 mm. Photos by Brian du Preez.

FIGURE 3. Known distribution of Aspalathus praetermissa (green circles) showing the encroaching impact of crop farming. [Source: “West Coast”, -32.5222888 18.610697.Afr.GIS Ltd. 2018. Google Digital Globe 2019. 26.04.2019.]