Indigofera wenholdiae du Preez & Schrire, 2021

Preez, Brian du, Dreyer, Leanne L., Stirton, Charles H., Muasya, A. Muthama & Schrire, Brian D., 2021, Indigofera wenholdiae (Indigofereae, Fabaceae), a new species from the Western Cape Province, South Africa, PhytoKeys 182, pp. 107-112 : 107

Indigofera wenholdiae du Preez & Schrire sp. nov.

Diagnosis.

Similar to I. brachystachya , but differs in its digitately compound, 5-7 foliolate leaves (versus pinnately compound, 7-9 foliolate leaves), leaflets 4-6 mm long (versus leaflets 9-15 mm long), racemes up to 7 mm long, flowers ± 4-5 per raceme (versus racemes> 10 mm long, flowers> 8 per raceme), flowers creamy white, unscented (versus flowers pale pink, scented), branching divaricate (versus branching random), populations restricted to sandstone fynbos (versus populations restricted to limestone fynbos).

Type.

South Africa, Western Cape Province, track to Beacon Peak in Grootbos Nature Reserve, Gansbaai District , elevation 257 m, 34°31'32.84"S, 19°30'19.08"E, 7 May 2020, flowering, B. du Preez 836 (Holotype: BOL!; Isotypes: K!, NBG!, PRE!) .

Description.

Erect perennial shrub 0.4-0.8 m tall, robust, sparsely branching, divaricate; obligate reseeder. Branches up to 10 mm thick, terete to ribbed on fresh growth, densely strigose with sessile whitish biramous hairs, glabrescent later, reddish-brown, woody. Stipules 0.8-1.2 mm long, ± 1 mm wide at base, broadly triangular, asymmetric, navicular-cucullate, attenuate, apex aristate, adpressed to branch, adnate to base of petiole, densely strigose, ± soft-textured and thickened, pale green, pearl bodies present along margin. Leaves alternate, digitately 5-7 foliolate, petiole ± 1 mm long, sub-terete, flattened adaxially; rachis ± 0.5 mm long, terete, stipels absent; petiolules ± 0.5 mm long; terminal leaflet 4-6 mm × 1.5-2.5 mm, narrowly oblanceolate, apex apiculate, hooked, base cuneate, upper surface sparsely strigose, bright green, paler below; lower surface densely strigose; mid-vein sunken adaxially, prominent abaxially; margins not thickened, strongly revolute; lateral leaflets similar, opposite. Racemes axillary, up to 7 mm long, erect, parallel with branch, roughly equalling the leaf length, including a peduncle 2-3 mm long, ribbed, soft-textured; ± 4-5 flowered; bracts ± 1.5 mm long, lanceolate, cucullate, apex apiculate, adpressed to petiole, persistent until after flowering, pearl bodies present along margin. Bracteoles absent. Pedicels 1-1.5 mm long. Flowers 8-9 mm long, unscented. Corolla creamy-white, petals persistent after anthesis. Calyx 3.5-4.2 mm long, pale green, lobes lanceolate, distinctly navicular-cucullate, 2.5-3 mm long, ± three times tube length, moderately strigose, pearl bodies present along margin. Standard petal 8.7-9.3 mm × 3.3-3.7 mm, broadly oblong, tapering gradually to a short claw at the base; blade concave, nectar guide plain white; apex acute-obtuse; back of standard strigose, no visible colouration patterns. Wing petals 7.5-8 × 1.5-2 mm, shortly clawed at base, unguiculate portion ± half total petal length, blade asymmetrically navicular, apex rounded; blade moderately strigose. Keel petals 7.5-8 × 1.8-2.3 mm, valvately connate distally, lateral spurs up to 1 mm long, blade asymmetrically lanceolate, dorsal margin curving slightly downwards to an acute-obtuse apex, densely strigose; claws 2.5-3 mm long. Stamens 5-5.5 mm long, exceeding calyx by 1.5-2 mm, staminal tube pale creamy-green; hair clusters present below anthers. Gynoecium 4-4.5 mm long, strigillose on distal half; style ± 2 mm long, erect to ± 1 mm high distally; stigma capitate. Fruit 13-16 × 2-2.2 mm, oblong, woody, reddish-brown, densely strigillose, 4-5 seeded, dehiscent, ripe fruit not seen. Seeds not seen.

Distribution, habitat and ecology.

Indigofera wenholdiae is restricted to a few sandstone hills from the Grootbos Nature Reserve to Pearly Beach on the Agulhas Plain of the Western Cape Province (Figure 2 ). The species is occasional in Overberg Sandstone Fynbos (FFs12, Mucina and Rutherford 2006), favouring south-facing slopes and hilltops.

Phenology.

Flowering takes place from April to July.

Etymology.

The specific epithet " Indigofera wenholdiae " is assigned in honour of Mrs Hannerie Wenhold who has funded large-scale conservation efforts in this area, including the funding of the botanist post at Grootbos Nature Reserve of Miss Rebecca Dames who brought this species to our attention in April 2020.

Conservation status.

Indigofera wenholdiae is a range-restricted species, with an EOO of 30 km2 and AOO of 24 km2. A total of six subpopulations across four locations have been discovered, with the number of mature individuals estimated to be less than 10 000. Most subpopulations occur within protected areas or on farms earmarked for conservation. Alien vegetation is prominent in the region, although only one location is currently threatened by invasive species, while alien eradication projects at other locations have largely controlled or eradicated invasive species. The Red List category VU D2 is thus recommended, based on the IUCN Categories and Criteria ( IUCN 2012).

Related species.

Indigofera wenholdiae is part of Section Indigofera Brachypodae , a large group ( ± 30 species) of Indigofera species almost exclusively found in Fynbos vegetation and characterised by having five or more foliolate leaves with short petioles. The I. brachystachya group resolves within this section and includes I. brachystachya , I. hamulosa and several putative undescribed taxa related to the former. All of these species are characterised by a corolla morphology unique in the genus, with elongate and concave standard petals and, in general, robust rather than delicate petals. All species in this group are coastally distributed and most often occur on limestone substrate. Apart from the distinguishing features noted above, I. wenholdiae is an erect to less than 1 m tall, divaricately branching shrub with deep green leaves and white flowers, in contrast with the bushier growth of I. brachystachya , with its typically dull grey leaves and pale pink flowers.

Additional specimens examined.

Grootbos Nature Reserve, (3419DA), 12 September 2020, B. du Preez 879 (BOL, NBG).

Figures

Figure 2. Distribution map of Indigofera wenholdiae.