Indigoferawenholdiae (Indigofereae, Fabaceae), a new species from the Western Cape Province, South Africa

Abstract In this study, Indigoferawenholdiae, a new species of Fabaceae from the Agulhas Plain Region of the Western Cape Province, South Africa, is described. A composite photographic plate is included along with a distribution map, description of habitat and ecology and proposed IUCN conservation status. Indigoferawenholdiae is unique in the I.brachystachya group by having digitately compound (vs. pinnately compound) leaves, white and unscented flowers (vs. pink and sweetly scented flowers) and grows on sandstone hillsides (vs. coastal limestone plains and outcrops).

(270+ species) in size (Dahlgren 1988;Schrire in Manning and Goldblatt 2012). Indigofera species in the CCR are largely part of a monophyletic clade referred to as the Cape Clade by Schrire et al. (2009). Unlike the three main tropical clades that have members dispersed across multiple continents, the Cape Clade is endemic to South Africa and especially within the winter-rainfall area (Schrire et al. 2009;Schrire in Manning and Goldblatt 2012). A large group within the Cape Clade, Section Brachypodae Schrire, is prolific in Fynbos vegetation and has many localised species, often associated with preferences for specific microhabitats. Diverse geological formations, as seen in the Agulhas Plain region (Thwaites and Cowling 1988), have resulted in localised radiations in many plant groups (Cowling and Holmes 1992;Manning and Goldblatt 2012). For example, over 20 new legume species have been recently described from various genera, including Aspalathus L., Otholobium C.H.Stirt., Polhillia C.H.Stirt., Psoralea L. and Rhynchosia Lour. (Curtis et al. 2013;Moteetee et al. 2014;Muasya 2016, 2017;Bello et al. 2017;Du Preez et al. 2021). Members of Indigofera Section Brachypodae, particularly the I. brachystachya group (I. brachystachya (DC.) E.Mey. and I. hamulosa Schltr.), are especially diverse in this region, with several putative undescribed taxa related to I. brachystachya, noted from recent field studies (Schrire and du Preez, unpublished data). While further, more detailed, analyses are required to resolve this species complex, we here describe a new, distinctive species from the I. brachystachya group first found in the Grootbos Nature Reserve in 2020.

Material and methods
The description of morphological characters is based on freshly collected material and herbarium voucher specimens. The conservation assessment 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). The distribution map was made using QGIS 3.18 software (www.qgis.org).
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 "wenholdiae" is assigned in honour of Mrs Hannerie Wenhold who has funded large-scale conservation efforts in this area, including Conservation status. Indigofera wenholdiae is a range-restricted species, with an EOO of 30 km 2 and AOO of 24 km 2 . 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 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.