Four new Indigofera (Fabaceae: Indigofereae) species from the Greater Cape Floristic Region

Abstract

Four new Indigofera species are described from the Greater Cape Floristic Region (GCFR). Indigofera barkeri is a new annual from the Richtersveld, with small flowers, 3.5À4.0 mm long, pinnately trifoliolate leaves and laterally flattened seeds. Indigofera dodii is endemic to the area around Cape Town, growing on granite and shaly slopes. It has apically congested racemes, flowers 6.0À6.5 mm long, digitately trifoliolate leaves, fruit with a hispid indumentum and tuberculate seed testas. Indigofera gariepensis, endemic to dry riverbeds in the eastern Richtersveld, is recognized by its alternate, silky-velutinous leaflets and calyx lobes § equal in length to its 5.5À6.5 mm long magenta flowers. Indigofera tanquana is known from only two collections and is endemic to the western Tanqua Karoo. It is easily recognized by its broad old grey stems, spinescent branches, simple grey-canescent leaves that aggregate on woody brachyblasts and reddish-magenta flowers. Detailed morphological descriptions are presented with composite photographic plates for each species. Notes on ecology, detailed diagnoses comparing with closely related species, a distribution map and an IUCN red list conservation assessment for each species is also provided.

Full text

Four new Indigofera (Fabaceae: Indigofereae) species from the Greater
Cape Floristic Region
B. du Preez
a,b,
*, B.D. Schrire
c
, L.L. Dreyer
b
, C.H. Stirton
a
, S.B.M. Chimphango
a
, A.M. Muasya
a
a
Bolus Herbarium, Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
b
Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
c
Honorary Research Associate, Accelerated Taxonomy Department,Royal Botanic Gardens, Kew, Richmond TW9 3AB, Surrey, UK
ARTICLE INFO
Article History:
Received 17 August 2023
Revised 19 September 2023
Accepted 3 October 2023
Available online xxx
Edited by Dr J. Manning
ABSTRACT
Four new Indigofera species are described from the Greater Cape Floristic Region (GCFR). Indigofera barkeri is
a new annual from the Richtersveld, with small flowers, 3.54.0 mm long, pinnately trifoliolate leaves and
laterally flattened seeds. Indigofera dodii is endemic to the area around Cape Town, growing on granite and
shaly slopes. It has apically congested racemes, flowers 6.06.5 mm long, digitately trifoliolate leaves, fruit
with a hispid indumentum and tuberculate seed testas. Indigofera gariepensis, endemic to dry riverbeds in
the eastern Richtersveld, is recognized by its alternate, silky-velutinous leaflets and calyx lobes §equal in
length to its 5.56.5 mm long magenta flowers. Indigofera tanquana is known from only two collections and
is endemic to the western Tanqua Karoo. It is easily recognized by its broad old grey stems, spinescent
branches, simple grey-canescent leaves that aggregate on woody brachyblasts and reddish-magenta flowers.
Detailed morphological descriptions are presented with composite photographic plates for each species.
Notes on ecology, detailed diagnoses comparing with closely related species, a distribution map and an IUCN
red list conservation assessment for each species is also provided.
© 2023 The Author(s). Published by Elsevier B.V. on behalf of SAAB. This is an open access article under the CC
BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Keywords:
Conservation
Desert
Fynbos
GCFR
Leguminosae
Namibia
Richtersveld
South Africa
Taxonomy
1. Introduction
Indigofera L. is a diverse genus comprising an estimated 100 spe-
cies (Schrire et al., 2009; Du Preez et al., in prep.) in the Greater Cape
Floristic Region (GCFR; Born et al., 2006). In a phylogenetic context,
most of this diversity resolves in the Cape Clade, while 14 of these
species resolve in the Tethyan Clade. In contrast, the Pantropical and
Paleotropical Clades are poorly represented in the GCFR (Schrire et
al., 2009; Du Preez et al., in prep.). Despite the diversity of Indigofera
globally, taxonomic work on the GCFR species has been sparse, with
the last published revision by Harvey (1862). Du Preez and Schrire
(unpublished data) have, through extensive field and herbarium stud-
ies, identified numerous undescribed Indigofera species from the GCFR,
with the first of a series of taxonomic revisions being published
recently (Du Preez et al., 2023). A new infrageneric classification of the
Cape Clade has been proposed (Du Preez et al., in prep.), paving the
way for further taxonomic revisions of different sections in this clade.
Two of the new subsections proposed in section Digitatae DC.
within the Cape Clade (Du Preez et al., in prep.), each contain a new
species, I. barkeri Du Preez & Schrire and I. dodii Du Preez & Schrire.
Indigofera barkeri is morphologically distinct and cannot be confused
with any other Indigofera species in the region, being the only annual
herbaceous Indigofera species with trifoliolate leaves that have oppo-
site-arranged lateral leaflets. It also occurs in an area with predomi-
nantly Tethyan Clade Indigofera species. Indigofera dodii is similar to I.
gracilis Spreng. and grows in the area around Cape Town on granite
outcrops.
Two new distinct species from the Tethyan Clade from within the
GCFR are also described. Indigofera gariepensis Du Preez & Schrire is
endemic to the eastern Richtersveld and is part of a group of five spe-
cies (I. alternans DC., I. auricoma E.Mey., I. exigua Eckl. & Zeyh., I. garie-
pensis and I. hololeuca Benth. ex Harv.) with alternate leaflets along
the rachis, which occur in the Greater Richtersveld area, belonging to
section Sessiliflorae (Baker) Schrire et al. (2009),Schrire (2012), (Du
Preez et al. in prep.). Indigofera tanquana Du Preez & Schrire is
endemic to the Tanqua Karoo, maturing into old, thick-stemmed
shrubs with spinescent branches. It forms part of section Amecarpus
(Harv.) Baker (Schrire, 1995), based on molecular phylogenies and
morphological data (Schrire et al., 2009; Du Preez et al., in prep.).
Three of the new species are endemic to the Extra Cape Region (ECR;
Snijman, 2013), while I. dodii is endemic to the Core Cape Region
(CCR; Manning and Goldblatt, 2012). This study describes these four
* Corresponding author at: Bolus Herbarium, Department of Biological Sciences,
University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa.
E-mail address: bdp@sun.ac.za (B. du Preez).
https://doi.org/10.1016/j.sajb.2023.10.003
0254-6299/© 2023 The Author(s). Published by Elsevier B.V. on behalf of SAAB. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/)
South African Journal of Botany 162 (2023) 680687
Contents lists available at ScienceDirect
South African Journal of Botany
journal homepage: www.elsevier.com/locate/sajb

new species, while also providing notes on their distribution, ecology,
and an IUCN red list conservation assessment for each species.
2. Materials and methods
Morphological species descriptions are based on freshly collected
material and herbarium specimens. Voucher specimens were studied at
BOL, GRA, K, NBG, PRE and WIND herbaria (acronyms according to Thiers,
2023). Finer details were observed using a Leica ES2 Stereo microscope,
and measurements were made using callipers. The conservation assess-
ment for each species was done using the categories and criteria of the
IUCN (2012). The Extent of Occurrence (EOO) and Area of Occurrence
(AOO) were calculated using GeoCAT (www.geocat.kew.org). Distribu-
tion maps were made using QGIS 3.18 software (www.qgis.org).
3. Taxonomy
3.1. Indigofera barkeri Du Preez & Schrire sp. nov.
Type: South Africa, Northern Cape, 2817 (Vioolsdrif): Richtersveld
National Park, in dry riverbed on way from De Koei camp site eastwards
into park (BC), 12 Sep 2000, Barker 1709 (GRA, holo.!; K, iso.!).
Indigofera sp. D, Schrire in Strelitzia 30: 388 (2013).
3.1.1. Description
Dwarf annual herb 50200 mm tall, laxly spreading. Branches terete,
ribbed, densely strigose, pale green, pearl bodies sparse. Stipules 12mm
long,upto0.5mmwideatbase,lanceolate-awl shaped, attenuate, fal-
cate, strigose, §membranaceous, glands present, reddish green. Leaves
pinnately trifoliolate; petiole 618 mm long, sub-terete, channelled;
rachis 13 mm long, extending beyond lateral leaflets, sub-terete, chan-
nelled, pearl bodies present; petiolules §0.70.9 mm long. Leaflets
516 £410 mm, obovate to ovate, apex emarginate, base cuneate;
adaxial surface strigose, pale green; abaxial surface densely strigose; mid-
vein dark green, not raised; margins somewhat thickened; slightly con-
duplicate; lateral leaflets opposite. Racemes up to 45 mm long, including
a peduncle of up to 10 mm, shorter than the subtending leaf, terete,
woody when dry; up to §18-flowered; bracts 1.01.5 mm long, subu-
late, caducous before anthesis; pedicels §0.5 mm long. Flowers
3.54.0 mm long, unscented; corolla magenta, caducous after pollina-
tion. Calyx 2.23.0 mm long, brownish; lobes lanceolate-subulate,
1.01.5 mm, §equalling the tube, clasping, sparsely strigose. Standard
34£2.93.9 mm, broadly obovate-reniform, tapering to a short claw
at the base, nectar flash violet with white rays emerging from central
white areola; blade sharply reflexed upwards for distal half of length;
apex emarginate; dorsal surface glabrous, pale. Wing petals
3.23.8 £1.11.5 mm, short-clawed at base, unguiculate portion §half
total petal length, asymmetrically oblanceolate, glabrous, apex obtuse.
Keel petals 3.03.3 £1.01.2 mm, lamina navicular, glabrous, apex
acute-attenuate, lateral spurs §0.5 mm long; claws 1.01.2 mm long,
broadening from the base. Stamens §2.02.5 mm long, slightly shorter
than calyx; anthers uniform, hairs absent. Pistil §2 mm long; ovary
§1.5 mm long, sessile, green, strigillose; style §1 mm long, erect to
§0.5 mm high distally; stigma capitate. Fruit 1321 £2.53.5 mm,
cylindrical, somewhat flattened, straight, brown-beige, densely strigil-
lose. Seeds 46perfruit,2.1£2.1 mm, square, laterally flattened, with
some latitudinal ridges, olive green (Fig. 1).
Flowering time: June to September (Rainfall dependent).
3.1.2. Etymology
The specific epithet “barkeri”is hereby assigned in honour of Prof.
Nigel P. Barker for his contribution to Indigofera research in South
Africa, including the collection of the type material of this species.
Fig. 1. Indigofera barkeri.1Flower front view; 2 Flower side view; 3 Flower ventral view; 4 Leaflets adaxial view; 5 Leaflets abaxial view; 6 Stipules; 7 Fruit; 8 
Whole plant in habitat. Scale bars: 2 mm. Photographs by B. du Preez.
B. du Preez, B.D. Schrire, L.L. Dreyer et al. South African Journal of Botany 162 (2023) 680687
681

3.1.3. Diagnostic characters and relationships
Similar to Indigofera gracilis and Indigofera dodii in being a reseed-
ing, herbaceous shrublet, but differs by being an annual (versus
perennial); leaves pinnately trifoliolate (versus digitately trifoliolate);
flower scattered along racemes (versus terminally clustered on race-
mes); distributed in the Greater Richtersveld region (versus distrib-
uted in the area around Cape Town). It belongs to a new proposed
monotypic subsect. Barkerae Du Preez & Schrire, as it has been shown
to be an early branching lineage in sect. Digitatae and morphologi-
cally distinct from the species in subsect. Gracilae Du Preez & Schrire
(Du Preez et al., in prep.).
3.1.4. Distribution and ecology
Indigofera barkeri has a scattered distribution from Namibia in the
L€
uderitz and Aus district, south through the Richtersveld to the
Eksteenfontein area (Fig. 2). Few records exist for this species, but
this could be ascribed both to how easily this species can be over-
looked, and the general lack of botanical exploration in the area. Indi-
gofera barkeri grows predominantly in open gravelly habitats, most
often in valleys and dry riverbeds. Vegetation types as described by
Mucina and Rutherford (2006) include Central Richtersveld Mountain
Shrubland (SKr1), Northern Richtersveld Scorpionstailveld (SKr7),
Noms Mountain Desert (Dg1), Richtersberg Mountain Desert (Dg2)
and Richtersveld Sheet Wash Desert (Dg3). It is an annual that only
appears after good rains and the small magenta flowers are likely pol-
linated by small bees.
3.1.5. Conservation status
The EOO and AOO calculated based on available data are 5000 km
2
and 44 km
2
, respectively. It is expected that this species is more com-
mon and widespread, as much of the region is poorly explored. Some
mining activity takes places within the distribution of I. barkeri, but
most known locations of the species occur within the protected area
of the Richtersveld Transfrontier National Park and Richtersveld
Community Conservancy, where no threats are evident. A red list
conservation assessment of Least Concern (LC) is suggested based on
the criteria of the IUCN (2012).
3.1.6. Additional notes
This species is superficially morphologically similar to Indigastrum
argyroides (E.Mey.) Schrire that occurs in similar habitats in the
region, but differs in having sparsely flowered inflorescences with a
maximum of 18 flowers (versus dense inflorescence with 2030
flowers); leaves trifoliolate, leaflets obovate to ovate, lateral leaflets
opposite (versus leaves 13 foliolate, leaflets ovate-orbicular, lateral
leaflets alternate or subopposite on trifoliolate leaves).
3.1.7. Further collections and localities
Namibia. KARAS: 2616 (L€
uderitz): L€
uderitz District, Klein Aus Lu 8
Farm, Glatter Raucken (CA), 26 Jun 1949, Kinges 2263 (PRE);
L€
uderitz, 15 Oct 1950, Kinges 2703 (PRE). South Africa. NORTHERN
CAPE: 2816 (Oranjemund): Western slope below Ploegberg, just off
road to Richtersveld (DB), 3 Sept 2019, Du Preez 720 (NBG). 2817
(Vioolsdrif): Richtersveld Nasionale Park, Onder Paradyskloof (AC),
18 Aug 1993, Zietsman & Links 2332 (PRE); Richtersveld; Zebra Kloof;
in kloof just north east of Rosyntjieberg (AC), 9 Oct 1991, Germishui-
zen 5583, 5584 (PRE); Richtersveld, Ploegwater, at southern end of
Ploegberg (CA), 7 Oct 1991, Germishuizen 5490 (BOL, PRE); Richters-
veld, c. 26 km from Eksteenfontein to Stewart’s Mine on road, camp-
ing spot (CB), 30 Aug 1987, Pienaar 1014 (PRE); Richtersveld, c.
10 km from Eksteenfontein - Cornells-Berg road, on way to Mount
Stewart (CD), 30 Aug 1987, Nicholas 2551 (PRE, 2 sheets).
3.2. Indigofera dodii Du Preez & Schrire sp. nov.
Type: South Africa, Western Cape, 3319 (Cape Town): Contour
path low on eastern side of Lions Head (CD), 26 Aug 2020, Du Preez
868 (BOL, holo.!; K!, NBG!, PRE!, iso.).
Indigofera sp. 6, Schrire in Strelitzia 9: 487 (2000); Schrire in Stre-
litzia 29: 553 (2012).
Indigofera setacea sensu Salter in Adamson & Salter, Fl. Cape Penin-
sula: 501 (1950), non E. Mey.
Indigofera pseudogracilis Schrire nom. nud.
3.2.1. Description
Prostrate to decumbent, laxly spreading, reseeding herb of up to
100 mm tall. Branches terete, ribbed, moderately strigose, olive green,
Fig. 2. Distributions of Indigofera barkeri (Red Circles), Indigofera gariepensis (Blue Rhomboids), Indigofera dodii (Yellow Squares) and Indigofera tanquana (Green Triangles).
B. du Preez, B.D. Schrire, L.L. Dreyer et al. South African Journal of Botany 162 (2023) 680687
682

pearl bodies sparse. Stipules 1.83.0 mm long, lanceolate-filiform,
spreading to recurved, sparsely strigose, §membranaceous, pearl
bodies present, reddish green. Leaves digitately trifoliolate; petiole
2.54.5 mm long, sub-terete, channelled, pearl bodies present, petio-
lules §0.71.0 mm long. Leaflets 49£3.05.8 mm, ovate to
broadly obovate, flat, apex apiculate, base cuneate; adaxial surface
glabrous, green, margin fringed with whitish hairs; abaxial surface
sparse to moderately strigose, concolorous, Racemes up to 50 mm
long, including a peduncle of up to 48 mm, many times longer than
the subtending leaf, terete, woody when dry; 36(8)-flowered, the
flowers terminally clustered, sub-umbellate; bracts 1.11.3 mm
long, lanceolate-subulate, caducous before anthesis; pedicels §
0.5 mm long. Flowers 6.06.5 mm long, unscented; corolla pink and
reddish, caducous after pollination. Calyx 3.54.0 mm long, reddish-
brown in bud becoming red; lobes lanceolate-awl shaped,
2.53.0 mm long, longer than the tube, spreading, sparsely strigose.
Standard 56£3.84.8 mm, broadly obovate, tapering to a short
claw at the base, nectar flash dark pink with radiating streaks; blade
sharply reflexed upwards for distal half of length; apex rounded,
shortly apiculate; dorsal surface largely glabrous with a few hairs
near apex. Wing petals 6.06.5 £2.02.5 mm, short-clawed at base,
unguiculate portion §half total petal length, asymmetrically spathulate,
strigillose only near base, apex acute to obtuse. Keel petals
4.75.2 £1.31.5 mm, lamina elliptic-navicular, hairy along dorsal
margin, apex acute, arcuate, lateral spurs §0.5 mm long; claws
2.02.3 mm long, broadening from the base. Stamens 3.74.0 mm
long, equal to calyx; anthers uniform, hairs present basally. Pistil
3.34.2 mm long; ovary 2.02.5 mm long, sessile, green, strigillose;
style 1.31.7 mm long, erect to §0.5 mm high distally; stigma capitate.
Fruit 914 £2.02.2 mm, cylindrical, slightly curved downwards, dark
brown, moderately hirsute. Seeds 57perfruit,1.6£1.3 mm, spheri-
cal-cylindrical, densely tuberculate, olive-green (Fig. 3).
Flowering time: July to October.
3.2.2. Etymology
The specific epithet “dodii”honours Mr Anthony H. Wolley-Dod, a
British soldier and botanist, for his contribution to botanical research
in South Africa, including one of the first collections of this species.
3.2.3. Diagnostic characters and relationships
Indigofera dodii is most similar to Indigofera gracilis, but differs in
being a prostrate to decumbent herb, 100 mm tall (versus herb sub-
erect, straggling through vegetation, 300500 mm tall); leaves ovate
to broadly obovate, petioles 2.54.5 mm long (versus leaves elliptic
to oblong, petioles 5.59.0 mm long); flowers 6.06.5 mm long, sta-
mens 3.74.0 mm long (versus flowers 4.25.0 mm long, stamens
2.83.0 mm long); fruit 914 mm long, 57-seeded (versus fruit
46 mm long, 23-seeded). These two species belong to a new pro-
posed subsect. Gracilae Du Preez & Schrire, as it has been shown to be
an early branching lineage in sect. Digitatae and morphologically dis-
tinct from the other proposed subsections (Du Preez et al., in prep.).
3.2.4. Distribution and ecology
Indigofera dodii is restricted to Cape Town, with a single collection
from the Worcester Division, although this locality is questionable
(Fig. 2). It grows prolifically post-fire in soils derived from granite
and sometimes shale, especially on the slopes around the Rhodes
Memorial and Lion’s Head. This species grows in vegetation types
described by Mucina and Rutherford (2006) as Peninsula Granite Fyn-
bos (FFg3) and Peninsula Shale Fynbos (FFh11).
3.2.5. Conservation status
The EOO and AOO calculated based on available data are 33 km
2
and 16 km
2
, respectively. This species is likely to have lost several
sub-populations with the expansion of Cape Town, especially in the
Camps Bay area. Most extant sites are within the Table Mountain
National Park. The remaining three known locations are threatened
Fig. 3. Indigofera dodii.1Flower front view; 2 Flower side view; 3 Flower ventral view; 4 Developing buds on inflorescence; 5 Leaf adaxial view; 6 Leaf abaxial view; 7
Stipules; 8 Inflorescence; 9 Whole plant in habitat. Scale bars: 2 mm (images 27), 5 mm (image 8). Photographs by B. du Preez.
B. du Preez, B.D. Schrire, L.L. Dreyer et al. South African Journal of Botany 162 (2023) 680687
683

by invasions of alien species, although the current number of mature
individuals is unknown and difficult to determine as the plants are
small and easily overlooked. A red list conservation assessment of
Endangered A2ac; B1ab(i,iii,iv,v) & B2ab(ii,iii,iv,v) is suggested based
on the criteria of the IUCN (2012).
3.2.6. Further collections and localities
South Africa. WESTERN CAPE: 3318 (Cape Town): Beyond Miller’s
Point (CD), 5 Jul 1896, Wolley-Dod 1252 (K); Kloof western slopes of
Lions Head (CD), 29 Aug 1897, Wolley-Dod 2785 (BOL, K); Ravine
above Camps Bay (CD), 1 Oct 1915, Pillans 3430 (BOL); Cape Penin-
sula, Camps Bay, Red Bank area (CD), Aug 1938, Penfold 57 (NBG);
Cape Peninsula, Table Mountain, slope beyond Slangolie Ravine
(CD), Aug 1939, Esterhuysen 1287 (BOL); Lions Mountain, above
Tamboors Kloof (CD), 14 Sep 1939, Salter 7636 (BOL); Cape Penin-
sula, Table Mountain, stony west slopes at foot of southern Twelve
Apostles (CD), 9 Aug 1953, Esterhuysen 21,705 (BOL). 3319 (Worces-
ter): La Motte State Forest, vicinity of Bakenkop, rocky SE facing slope
(CC), 18 Aug 1983, Forsyth 283 (PRE).
3.3. Indigofera gariepensis Du Preez & Schrire sp. nov.
Type: South Africa, Western Cape, 2817 (Vioolsdrif): Vioolsdrif.
Arid gravel plains 1215 km north of Noordoewer (DA), 18 Jul
1984, Goldblatt 7141 (K, holo.!; PRE!, WIND, iso.).
Indigofera sp. A, Schrire in Strelitzia 30: 387 (2013).
Indigofera maritima sensu Raimondo et al. (2009),non Baker, pro
parte.
3.3.1. Description
Prostrate or procumbent annual, sometimes a short-lived peren-
nial herb, 1030 mm tall, spreading. Branches up to 5 mm wide,
terete, ribbed, hirsute, brownish-green to green; pearl bodies absent.
Stipules 3.55.0 mm long, lanceolate-subulate, attenuate, spreading,
strigose-silky abaxially, §membranaceous, pearl bodies sparse on
margin. Leaves pinnately 57 foliolate, petiole 610 mm long, sub-
terete, ribbed; rachis 723 mm long, sub-terete, ribbed, stipels
absent; petiolules §1 mm long. Leaflets 717 £511 mm, obovate
to ovate, apex apiculate, base cuneate; adaxial surface densely silky-
velutinous, dark green; abaxial surface densely silky-strigose; mid-
vein sunken above, prominent abaxially; margins flat to slightly con-
duplicate; lateral leaflets similar, alternate. Racemes up to 30 mm
long, including a peduncle of up to 13 mm, shorter than the subtend-
ing leaf, terete, flexible; up to §2030-flowered; bracts 2.73.7 mm
long, linear-ensiform, caducous before anthesis; pedicels §0.5 mm
long. Flowers 5.56.5 mm long, unscented; corolla magenta, cadu-
cous after pollination. Calyx 4.56.5 mm long, dark burgundy; lobes
linear-ensiform, 35 mm, §two to more than three times longer
than tube, plumose setaceous. Standard 5.87.2 £5.07.2 mm,
ovate, tapering to a short claw at the base, nectar flash maroon rays
emerging from central burgundy areola; blade erect from base, sides
somewhat reflexed; apex emarginate; dorsal surface strigose along
and around midline and upper half of blade, pale. Wing petals
5.06.2 £2.12.8 mm, short-clawed at base, unguiculate portion §
half total petal length, asymmetrically obovate, glabrous, apex acute.
Keel petals 5.16.1 £1.82.3 mm, lamina ovate-navicular, strigose
along margin, apex apiculate, lateral spurs §1 mm long; claws
1.82.2 mm long, broadening from the base. Stamens 4.55.0 mm
long, equal to or shorter than calyx; anthers uniform, hairs basal on
carinal anther. Pistil 4.04.6 mm long; ovary 1.72.0 mm long, green,
strigillose; style 3.53.8 mm long, erect to §1.5 mm high distally;
stigma capitate. Fruit 5.510.0 £1.52.2 mm, cylindrical, laterally
compressed between seeds, densely strigillose-hispid, 24-seeded.
Seeds 1.21.4 £1.11.3 mm, spherical, toffee brown (Fig. 4).
Flowering time: June to January (Rainfall dependent).
3.3.2. Etymology
The specific epithet “gariepensis”refers to the Lower Gariep
region where this species is found. The word “Gariep”is derived from
the Khoekhoe dialect meaning “River”, which refers to the Orange
River, the primary water source in the area.
3.3.3. Diagnostic characters and relationships
It is most similar to Indigofera maritima Baker with which it has
been often confused or considered conspecific with. Indigofera mari-
tima is, however, geographically very distinct (Coastal southern
Angola) and differs morphologically by having a 4.56.5 mm long
calyx, with linear-ensiform lobes (versus calyx 3.04.5 mm long,
lobes lanceolate-subulate); leaves with a densely silky-velutinous
indumentum (versus leaves with an adpressed strigose indumentum
adaxially); style 3.53.8 mm long (versus 2.02.5 mm long). In the
Richtersveld region it is most similar in appearance to I. auricoma E.
Mey and I. hololeuca Benth. ex Harv. but differs in having densely
silky-velutinous hairy leaves and hirsute stems (versus adpressed
canescent-strigose leaves and stems); calyx lobes that are two to
three times longer than the tube (versus calyx lobes that are equal to
or up to two times longer than the tube). The racemes of I. auricoma
are also substantially longer at over 100 mm long (versus up to
30 mm long in I. gariepensis), and I. hololeuca has smaller flowers at
45 mm long (versus 5.56.5 mm in I. gariepensis). These species all
belong to section Sessiliflorae in the Tethyan Clade based on molecu-
lar data and a shared character of having alternately arranged lateral
leaflets along the rachis (Schrire et al., 2009; Du Preez et al., in prep.).
3.3.4. Distribution and ecology
Indigofera gariepensis has a distribution from southern Namibia in
the Warmbad area, south to the Vioolsdrif area in the south-eastern
Richtersveld (Fig. 2). Few records exist for this species, but this can be
ascribed to the general lack of botanical exploration in the area, and
the scarcity of sufficient rainfall required for this species to emerge
and flower. Indigofera gariepensis grows predominantly in open grav-
elly habitats across its distribution, favouring dry riverbeds and open
gravel plains. It grows in Kahams Mountain Desert (Dg5), Northern
Nababiepsberge Mountain Desert (Dg7), Southern Nababiepsberge
Mountain Desert (Dg8) and Eastern Gariep Rocky Desert (Dg10) vege-
tation types (Mucina and Rutherford, 2006). It is an annual that only
appears after good rains.
3.3.5. Conservation status
The EOO and AOO calculated based on available data are 624 km
2
and 28 km
2
, respectively. It is likely that this species is more common
and widespread than the current data suggests as this area is under-
explored, and plants only appear after sufficient rains, which are a
rare event. One of the two known locations in South Africa are threat-
ened by illegal vehicle (4 £4) activity in the riverbed where this pop-
ulation grows. Populations on the Namibian side are largely not
threatened. A red list conservation assessment of Least Concern (LC)
is suggested based on the criteria of the IUCN (2012).
3.3.6. Further collections and localities
Namibia. KARAS: 2817 (Vioolsdrif): Hunsberge, Assenkehr (CB),
21 Sep 1989, Jurgens 28,897 (WIND); Vioolsdrif, 8 km North of Noor-
doewer, Stony flat between table mountains, shallow rivulet (DA),
18 Jul 1984, Giess 14,539 (PRE, WIND); Shale hills north of Rooival,
near the Orange River, Namibia (DA), Sep 1931, Pillans 6423 (BOL,
K); Vioolsdrift District, Noordoewer, 1215 km north of Noordoewer
(DA), 18 Jul 1984, Goldblatt 7141 (K, PRE, WIND); Warmbad district,
13 miles SW of farmhouse Witputs, river entrance (Haib River) to
Orange River, in riverbed (DD), 11 Sep 1963, Merxm€
ueller & Giess
3636 (PRE, WIND). South Africa. NORTHERN CAPE: 2817 (Vioolsdrif):
Geelfontein (CD), 22 Sep 1981, Van Jaarsveld & Kritzinger 6333
(NBG); Vioolsdrif District., roadside pass through mountains near
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Orange River at Vioolsdrift (DA), 27 Jan 1974, Clark 643 (K, PRE,
PRU); Vioolsdrif, just outside Vioolsdrif (DA), 15 Aug 1967, Van der
Schijff 8214 (PRE, PRU); Aug 1967, Van der Schijff 8257 (PRE, PRU);
Dry sandy bed of Khusies River near Vioolsdrift, low hills about 1
mile SE of Vioolsdrift (DA), Sep 1931, Pillans 6381 (BOL, K); Dry riv-
erbed about 1 km SE of Viooldrif (DA), 12 Aug 2020, Du Preez 862
(BOL, NBG).
3.4. Indigofera tanquana Du Preez & Schrire sp. nov.
Type: South Africa, Western Cape, 3219 (Wupperthal): Just west
of De Hoop campsite on rocky outcrops above Doring River (DA), 13
Aug 2022, Du Preez 981 (BOL, holo.!; K!, NBG!, PRE!, iso.).
3.4.1. Description
Erect to spreading, woody, reseeding shrub 0.31.0 m tall.
Branches terete, ribbed, becoming spinescent, canescent, then glab-
rescent, greygreen becoming beige, silvery grey on old stems; pearl
bodies absent. Stipules §1 mm long, triangular, canescent, §mem-
branaceous, pearl bodies present. Leaves simple, 49£12 mm, lin-
ear-oblanceolate, sharply arcuate towards apex, conduplicate, sessile,
canescent, apex apiculate, base cuneate, sub-fasciculate on woody
brachyblasts. Racemes up to 34 mm long, including a peduncle of up
to 6 mm, longer than the subtending leaf, terete, woody when dry;
39-flowered; bracts §1 mm long, lanceolate-subulate, persistent
after anthesis; pedicels §1.5 mm long. Flowers 67 mm long,
unscented; corolla reddish-magenta, caducous after pollination. Calyx
2.22.8 mm long, green flushed blackish; lobes lanceolate-subulate,
1.01.7 mm, §equalling to longer than tube, spreading, densely stri-
gose. Standard 6.57.5 £56 mm, ovate, tapering to a short claw at
the base, nectar flash dark maroon with radiating streaks; erect from
base; apex apiculate; dorsal surface densely strigose, pale. Wing pet-
als 67£2.23.0 mm, short-clawed at base, unguiculate portion §a
third of total petal length, obovate, glabrous, apex obtuse-rounded.
Keel petals 67£2.22.5 mm, lamina obovate-navicular, hairy along
margin, apex acute, lateral spurs 0.50.8 mm long; claws
2.22.8 mm long, broadening from the base. Stamens 5.56.0 mm
long, far exceeding calyx; anthers uniform, hairs present. Pistil
5.56.0 mm long; ovary 2.32.5 mm long, 24-ovulate, sessile,
green, strigillose; style 3.23.5 mm long, erect to 1.21.5 mm high
distally; stigma capitate. Fruit 1320 £2.73.5 mm, tetragonous,
straight, greenish brown, moderately strigillose. Seeds not seen.
(Fig. 5).
Flowering time: June to August.
3.4.2. Etymology
The specific epithet “tanquana”denotes the endemic status of the
species in the Tanqua Karoo.
3.4.3. Diagnostic characters and relationships
Morphologically resembling Indigofera obcordata Eckl. & Zeyh., but
differs in having exclusively simple leaves, sub-fasciculate on woody
brachyblasts, linear-oblanceolate, 49£12 mm (versus leaves 13
foliolate, not sub-fasciculate, oblanceolate-obovate-cuneate,
510 £2.55.0 mm); racemes to 34 mm long (versus racemes to
6 mm long); stamens and pistil 5.56.0 mm long (versus stamens
and pistil 4.04.5 mm long); distribution in western Tanqua Karoo
(versus distribution in Little Karoo to Steytlerville Karoo). It is a mem-
ber of section Amecarpus in the Tethyan Clade based on molecular
data and morphological characters (Schrire et al., 2009; Du Preez et
al., in prep.).
Fig. 4. Indigofera gariepensis.1Flower front view; 2 Flower side view; 3 Flower ventral view; 4 Single leaf and developing inflorescence; 5 Leaflets adaxial view; 6 Leaf-
lets abaxial view; 7 Stipules; 8 Mature inflorescence; 9 Whole plant in habitat. Scale bars: 2 mm (images 23 and 7); 5 mm (images 46 and 8). Photographs by B. du Preez.
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3.4.4. Distribution and ecology
Indigofera tanquana is only known from the De Hoop Camp Site
farm and Kleine Zadelmakers Bank in the western Tanqua Karoo
(Fig. 2). The area is expansive, arid, inaccessible, and better known for
its succulent diversity. This species was found growing on sandstone
outcrops adjacent to the Doring River in vegetation described as
Swartruggens Quartzite Karoo (SKv2) by Mucina and Rutherford
(2006). It may be more widespread as this vegetation type is exten-
sive in the western Tanqua Karoo and warrants further exploration.
3.4.5. Conservation status
The EOO and AOO calculated based on available data are 19 km
2
and 12 km
2
, respectively. This species does not appear to face any
immediate threats and is not adversely affected by livestock brows-
ing. Climate change and increased aridification may, in future, pose a
threat, but no other anthropogenic threats are present or predicted.
It may also be found to be more widespread and numerous once fur-
ther exploration of the area takes place. A red list conservation
assessment of VU D2 is suggested based on the criteria of the IUCN
(2012) due to the highly localized distribution and potential future
threats posed by climate change.
3.4.6. Further collections and localities
South Africa. WESTERN CAPE: 3219 (Wupperthal): Kleine Zadel-
makers Bank between De Bos and Uitspankraal (AC), 2 Jun 1989,
Snijman 1219 (PRE).
Declaration of Competing Interest
The authors hereby confirm that there is no conflict of interest
with regard to this manuscript.
Acknowledgments
Permits for the collection of herbarium specimens were obtained
from SANParks (DUPR-B/2019-025), Northern Cape Department of
Environment and Nature Conservation (FLORA 0133/2020), Western
Cape Nature Conservation Board (Permit: AAA 008-00222-0028) and
Eastern Cape Parks and Tourism Agency (RA 0310). The first author
was financially support by the Science Faculty PhD Fellowship, Uni-
versity of Cape Town (UCT), and NRF FBIP bursary (FBIP 128327).
Running costs for research, including fieldwork, were covered
by an NRF FBIP grant awarded to Prof. A.M. Muasya
(FBIP180529337017). Financial support for a research visit to RBG,
Kew Herbarium were obtained from the IAPT and NRF. The curators,
staff and volunteers of K (Dr Gwilym Lewis and Dr Xander van der
Burgt), BOL (Dr Cornelia Klak and Charlene Christian), NBG (Dr
Anthony Magee), PRE (Erich van Wyk), and SCHG (Jennifer Potgieter)
herbaria are thanked for allowing access to their facilities and kind
hospitality during research visits.
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