Two new species of Indigofera L. (Leguminosae) from the Sneeuberg Centre of Floristic Endemism, Great Escarpment (Eastern and Western Cape, South Africa)

Abstract Two new species of Indigofera L. (Leguminosae) are described from the Sneeuberg Centre of Floristic Endemism on the southern Great Escarpment, Eastern and Western Cape Provinces, South Africa. Both species are localised high-altitude endemics. Indigofera magnifica Schrire & V.R. Clark is confined to the summit plateau of the Toorberg–Koudeveldberg–Meelberg west of Graaff-Reinet, and complements other western Sneeuberg endemics such as Erica passerinoides (Bolus) E.G.H. Oliv. and Faurea recondita Rourke & V.R. Clark. Indigofera asantasanensis Schrire & V.R. Clark is confined to a small area east of Graaff-Reinet, and complements several other eastern Sneeuberg endemics such as Euryops exsudans B. Nord & V.R. Clark and Euryops proteoides B. Nord. & V.R. Clark. Based on morphology, both new species belong to the Cape Clade of Indigofera, supporting a biogeographical link between the Cape Floristic Region and the Sneeuberg, as well as with the rest of the eastern Great Escarpment.


Introduction
Th e genus Indigofera L. (Leguminosae) is a large genus comprising some 750 taxa worldwide, with the majority (ca. 550) occurring in Africa and Madagascar (Schrire et al. 2009). In South Africa, Indigofera is represented in all biomes, but is particularly well represented in the Cape Floristic Region and the eastern Great Escarpment. Th e discovery of two new Indigofera species from the Sneeuberg Centre of Floristic Endemism ) supports the view that continued fi eld exploration is essential for biodiversity and biogeographical research in South Africa (Robertson and Barker 2006). Th is paper describes these two Indigofera species, complementing the descriptions of several other Sneeuberg discoveries since 2005 (Goldblatt and Manning 2007, Nordenstam et al. 2009, Stirton et al. 2011, Rourke et al. 2013.

Materials and methods
Th e species were originally discovered in 2006 during intense plant collecting on the Sneeuberg as part of a plant diversity and biogeographical study of the southern Great Escarpment (Clark 2010). Extensive sampling from 2006-2012 in areas adjacent to the known populations of each species has not revealed other populations. Several return trips to the respective populations since their discoveries were necessary before suitable fruiting material could be obtained.

Species treatments
Indigofera magnifi ca Schrire & V.R. Clark, sp. nov. urn:lsid:ipni.org:names:77146131-1 Figs 1, 2; Plate 1 Diagnostic characters. Indigofera magnifi ca is morphologically similar and most closely related to I. meyeriana Eckl. & Zeyh., but diff ers in its prostrate, compact, densely matted habit (vs. laxly spreading, less dense and diff use habit), sparsely to moderately strigose becoming reddish-maroon and glabrescent stems (vs. green-grey to canescent), fewer fl owers (±3-8) per raceme (vs. >8), brighter, more vivid pink fl owers (vs. paler pink), and sparsely, appressed hairy pods (vs. spreading hairy pods). Th e overall colour of plants of I. magnifi ca is a darker green than the generally greygreen to grey appearance of I. meyeriana. Indigofera meyeriana is common and widespread in the Western Cape and western Northern Cape Provinces, and also occurs on the Sneeuberg.
Etymology. Th e specifi c epithet magnifi ca is derived from the Latin adjective magnicus -a -um (a. splendid, magnifi cent) and is named for the magnifi cent, showy, vivid fuchsia-pink fl owers.
Distribution and ecology. Indigofera magnifi ca is confi ned to the summit plateau of the Toorberg-Koudeveld-Meelberg in the western Sneeuberg, between 1700-2150 m. Th e species is occasional to abundant, found exclusively on the dolerite-derived loamy-clays and black turf soils typical of this plateau. Th e vegetation type is Karoo Escarpment Grassland (Gh1, Mucina and Rutherford 2006), typical of high altitudes in the Sneeuberg mountain complex, with the dominant grass species being Tenaxia (=Merxmuellera) disticha (Nees) N.P. Barker , 2012, Rourke et al. 2013.
Conservation status. While the extent of occurrence (EOO) of Indigofera magnifi ca is small (ca. 30 km 2 ), it is common (probably >10 000 individuals) in its restricted area. Th ere are no obvious risks from the current land-use of livestock grazing: plants do not show evidence of damage from foraging or trampling. Th e remote, rocky high-altitude habitat renders it relatively safe from other detrimental land-use. Already restricted to summit elevations, it is however potentially at risk from global climate change. Any potential wind farm proposals for the Toorberg-Koudeveld-Meelberg would place this species at serious risk. Th e category VULNERABLE (Vu D2) is thus recommended.   Indigofera asantasanensis may also be confused with I. burchellii DC., being similar in having digitately 5-7 foliolate leaves, but it has wider stipules (1-1.6 mm vs. < 0.5 mm). Indigofera alpina is mostly confi ned to the mountains of the Eastern Cape, while I. burchellii is almost exclusively a southern Great Escarment species, centred from the Roggeveldberge to the Eastern Cape Drakensberg; both of these species also occur in the Sneeuberg.
Etymology. Th e species is named for the Asante Sana Private Game Reserve, the owners and managers of which have been generous and instrumental in facilitating biodiversity research in the Sneeuberg. Th e known range of this species is almost entirely confi ned to this property. Distribution and ecology. Indigofera asantasanensis is currently only known from a small area in the eastern Sneeuberg from the Nardousberg to the Tandjiesberg-Coetszeesberg area behind the old town of Petersburg (now incorporated in the Asante Sana Private Game Reserve) and Pearston. Th e Tandjiesberg here is not to be confused with the more familiar Tandjiesberg (32°23'13"S, 24°42'13"E) of lower altitude and closer to Graaff -Reinet. Indigofera asantasanensis occurs from the mid-upper slopes to the summit plateau, ca. 1500-2200 m; it is locally abundant in Karoo Escarpment Grassland (Mucina and Rutherford 2006), dominated in this locality by inter alia Tenaxia disticha, Euryops trilobus Harv. and Helichrysum splendidum (Th unb.) Less. Indigofera asantasanensis occurs in loamy, rocky soils derived from both dolerite and Beaufort Group sandstone substrates. It compliments several local endemics, including Euryops proteoides B. Nord. & V.R. Clark and E. exsudans B. Nord. & V.R. Clark (Nordenstam et al. 2009

Biogeography
Including these two described species, some 20 of the Sneeuberg's ca. 26 endemic species are concentrated in the moister south-western and south-eastern scarp areas.
Sixteen species are local to one or the other of these two areas, the other four species with populations separated by the internal 'Sunday's River Interval' , Stirton et al. 2011. Only one endemic (Hilliard and Burtt's 1985, Conium sp. no. 4) occurs throughout the Sneeuberg, and a further three can be considered arid-adapted. Th is suggests that endemism in the Sneeuberg is driven by the availability of moisture, or that the moister scarp slopes and adjacent summits are climatic refugia for previously more widespread species . Th is mirrors the patterns evident in the Main Drakensberg (Pooley 2003) and the Great Winterberg-Amatholes , where endemism is also highest on the wettest scarps and summits. Indigofera magnifi ca and I. asantasanensis show extreme versions of this localism, being confi ned to unusually small areas on the summit in the west (I. magnifi ca) and on the moist scarp slope in the east (I. asantasanensis). Both are also located in the Cape Clade of Indigofera (Schrire et al. 2009), supporting a biogeographical connection between the Sneeuberg and the Cape Floristic Region, as well as with the rest of the eastern Great Escarpment.