DOI: 10.5061/dryad.bg79cnpgx
title: A taxonomic revision of the Argyrolobium robustum and A. transvaalense groups (Fabaceae) in southern Africa

description: Previous studies on the genus Argyrolobium (Genisteae, Fabaceae) in
 southern Africa recognized a group of species defined by a suffrutescent
 habit, monomorphic flowers and leaves, and the plants not turning black
 when dried as ‘section A. transvaalense’. A formal rank was never
 published for this group. Here a taxonomic study of this group is
 conducted, including comprehensive descriptions of and a key to the
 species, nomenclature, typifications, diagnostic characters, and
 geographical distribution. Based on an assessment of morphological
 characters, two groups can be recognised; 1) the A. robustum group that
 comprises four species with a herbaceous habit with up to 55-flowered
 inflorescences, flowers drying black or turning black when damaged, keel
 petals lacking pockets, and staminal sheaths fully open above, and 2) the
 A. transvaalense group comprising five species with a suffruticose habit
 with up to 24-flowered inflorescences, flowers becoming discoloured
 (darker coloured or brown) when dried, keel petals with pockets except in
 A. megarhizum, and staminal sheaths variously fused into a closed tube.
description: Literature and herbarium
 material (including types) from JSTOR Global Plants (2022), AMD, B, BM,
 BOL, E, G, HBG, J, JE, K, L, M, MEL, MO, NBG (including SAM), NH, NU, PRE,
 REG, S, TCD, TUB, and UPS (herbarium acronyms according to Thiers 2023)
 were studied and used to delimit species following standard
 alpha-taxonomic methods. Specimens were arranged into morpho types based
 on overall morphological similarities and distributions. For each morpho
 type, three measurements of each vegetative and some reproductive
 (inflorescences, bracts, bracteoles, fruits and seeds) characters were
 taken from a minimum of five specimens, and where available,
 representative of the full range of variation. From these, one flower
 (where available) per specimen was rehydrated, dissected, and flower parts
 measured. Larger plant parts were measured with a ruler while
 micromorphological characters were photographed and measured using an
 Olympus DSX110 digital microscope with Olympus DSX software v. 3.1.9
 (Olympus Corporation 2011-2019). Diagnostic characters were identified and
 used to describe taxa. In addition, fieldwork was conducted in the
 Limpopo, Mpumalanga, and KwaZulu-Natal Provinces (South Africa) to observe
 plants in their natural habitat. Photos were taken using a Canon EOS 450D
 with a 100 mm Canon macro lens (Canon Inc.).
 Specimens with sufficient
 locality information were georeferenced following the Natural Science
 Collections Facility protocol (Englebrecht 2021) and distribution maps
 generated with QGIS v. 3.22.7-Bialozieza software (© 1989, 1991 Free
 Software Foundation, Inc.).
description: # A taxonomic revision of the *Argyrolobium robustum* and *A.
 transvaalense* groups (Fabaceae) in southern Africa
 [https://doi.org/10.5061/dryad.bg79cnpgx](https://doi.org/10.5061/dryad.bg79cnpgx) The dataset includes two tables and six figures, supporting and illustrating the findings of the taxonomic revision. The two tables summarises vegetative (table 1) and reproductive (table 2) diagnostic characters that were used to distinguish among the nine species. The six figures illustrate the vegetative and reproductive morphology of the *A. robustum* (figures 1, 2, 4) and *A. transvaalense* (figures 2, 3, 5) groups as well as the distribution of all nine species (figure 6). ## Description of the data and file structure Tables 1 and 2 should be used in combination with figures 1-6 and the revision to distinguish among the nine species recognised in the *A. robustum* and *A. transvaalense* species groups. Table 1 provides a summary of seven vegetative diagnostic characters and table 2 a summary of eleven reproductive diagnostic characters. In-text references to the tables and figures are provided in the revision. The figure legends and table headings are provided below. Table 1. Seven vegetative diagnostic characters to distinguish among the nine species of the *Argyrolobium robustum* and *A. transvaalense* groups. Table 2. Eleven reproductive diagnostic characters to distinguish among the nine species of the *Argyrolobium robustum* and *A. transvaalense* groups. Figure 1. Habit and diagnostic characters of species in the *Argyrolobium robustum* group. A. Habit of *A. baptisioides*, showing the branched stems and many-flowered inflorescences. Note the relatively short height of the plants in comparison with the surrounding vegetation. B. Closely arranged flowers of *A. baptisioides* with obovate-panduriform standard petals. The flower petals turn black when damaged or dried. C. Oblanceolate leaflets of *A. baptisioides* with a pilose indumentum abaxially. D. Upwardly directed fruits of *A. baptisioides*, typical of the tribe Genisateae. E. A herbarium specimen of *A. speciosum* showing the leaves arranged close to the base of the stem. F. An entire plant of *A. longifolium* showing the dimorphic leaves with obovate leaflets at the base and narrowly elliptic leaves at the top. The plants are relatively tall with stems branching only in the upper half. G. Laxly arranged inflorescences of *A. longifolium*. H. A flower of *A. longifolium* from the front, showing the obovate-panduriform standard petal. I. A flower of *A. longifolium* from the side, showing the bilabiate calyx (typical for the tribe Genisteae) and the obovate-panduriform standard petal. J. Narrowly elliptic upper leaflets of *A. longifolium* showing the sericeous abaxial surface. K. Obovate lower leaflets of *A. longifolium* showing its glabrous adaxial surface. L. Habit of *A. robustum* with leaves arranged all along the stems. Also note that the stems are unbranched and virgate when multiple stems are present. M. Many-flowered inflorescence of *A. robustum* displaying red-coloured veins on the adaxial side of the standard petal and tips of the wing petals. N. A fruit-bearing inflorescence of *A. robustum*. A–D, F–N taken by Marianne le Roux, E (NU0081700) provided by the Bews Herbarium (NU). Figure 2. Androecial morphology of the *Argyrolobium robustum* and *A. transvaalense* groups. A. A young staminal sheath closed above, forming a tube. This configuration is present in all species of the *A. robustum* group. B. A staminal sheath open above. This configuration is present in all species of the *A. transvaalense* group. A. *Argyrolobium longifolium*, *Thode 3032* (PRE). B. *A. transvaalense*, *Van der Sijff 6623* (PRE). Scale bar: 2 mm. Figure 3. Habit and diagnostic characters of species in the *Argyrolobium transvaalense* group. A. Habit of *A. megarhizum*. B. Flowers of *A. megarhizum*. Note the glabrous standard and wing petals with sculpturing. C. Pilose abaxial leaflets of *A. megarhizum*. D. Habit of *A. muddii*. E. Flowers of *A. wilmsii* with densely sericeous-tomentose calyces and sericeous-tomentose standard petals. F. Sparsely pilose adaxial and pilose abaxial leaflets of *A. muddii*. G. Densely sericeous adaxial and abaxial leaflets of *A. wilmsii*. H. Habit of *A. frutescens* displaying terminal and axillary inflorescences. I. Habit of *A. wilmsii* showing the typical silver appearance due to its dense indumentum often observed in this species. J. Inflorescence of *A. transvaalense* showing the sericeous calyces. K. Glabrous adaxial and sericeous abaxial leaflets of *A. transvaalense*. L. Habit of *A. transvaalense*. A–G, I–L taken by Marianne le Roux, H taken by Delia Oosthuizen. Figure 4. Floral parts showing differences in size, shape, and vestiture, used in combination to distinguish among the species of the *Argyrolobium robustum* group. A1–D1. Calyces (upper lobes to the left). A2–D2. Standard petals. A3–D3. Wing petals. A4–D4. Keel petals. A. *Argyrolobium baptisioides*. B. *A. longifolium*. C. *A. robustum*. D. *A. speciosum*. A1. *Haygarth s.n.* (*TRV 22780*) (PRE). A2–4. *Flanagan 2141* (PRE). B1. *Germishuizen 1805* (PRE). B2–4. *Strey 8384* (PRE). C1. *Dlamini A2698* (PRE). C2–4. *Stirton 5081* (PRE). D1–4. *Sim 20165* (PRE). Scale bar: 2 mm. Figure 5. Flower parts showing differences in size, shape, and vestiture, used in combination to distinguish among the species of the *Argyrolobium transvaalense* group. A1–D1. Calyces (upper lobes to the left). A2–D2. Standard petals. A3–D3. Wing petals. A4–D4. Keel petals. A. *Argyrolobium frutescens*. B. *A. megarhizum*. C. *A. muddii*. D. *A. transvaalense*. E. *A. wilmsii.* A1–4. *Meyer 1874* (PRE). B1–4. *Grobbelaar 606* (PRE). C1–4. *Edwards 654* (PRE). D1. *Galpin 11372* (PRE). D2–4. *Van der Schijff 6623* (PRE). E1. *Meyer 6872* (PRE). E2. *Prosser 1488* (PRE). Scale bar: 2 mm. Figure 6. Distribution maps of the species in the *Argyrolobium robustum* and *A. transvaalense* groups in southern Africa. A. *A. baptisioides.* B. *A. longifolium*. C. *A. robustum* (black circles) and *A. speciosum* (white circles). D. *A. frutescens*. E. *A. megarhizum*. F. *A. muddii*. G. *A. transvaalense*. H. *A. wilmsii*. ## Sharing/Access information Information provided in the tables and figures derived from fieldwork conducted in the Gauteng, Limpopo, KwaZulu-Natal and Mpumalanga Provinces in South Africa, literature studies, herbarium studies of specimens in AMD, B, BM, BOL, E, G, HBG, J, JE, K, L, M, MEL, MO, NBG (including SAM), NH, NU, PRE, REG, S, TCD, TUB, and UPS (herbarium acronyms according to Thiers 2023), and image studies in JSTOR Global Plants (https://plants.jstor.org/). All representative specimens studied are listed in the revision with each species treatment. ## Code/Software Distribution maps were generated in QGIS v. 3.22.7-Bialozieza software (© 1989, 1991 Free Software Foundation, Inc.) using latitude and longitude values obtained from georeferencing of herbarium specimens following the Natural Science Collections Facility protocol (Englebrecht 2021).