Aristea rufobracteata ( Iridaceae : Aristeoideae ) , a new species from the southern Western Cape , South Africa

In the course of a review of herbarium collections of Aristea Aiton, we identified specimens of tall plants with hairless, reddish brown inflorescence spathes and bracts from the Langeberg, Outeniqua, Tsitsikamma and Baviaanskloof mountains in South Africa as an undescribed species. These collections were identified as Aristea bakeri Klatt or Aristea capitata (L.) Ker Gawl. [or their synomyms Aristea confusa Goldblatt, Aristea major Andrews or Aristea thyrsiflora (D.Delaroche) N.E.Br.], following Weimarck (1940), who included several early collections of the taxon from the George and Knysna districts of the southern Western Cape in his circumscription of A. capitata. The name A. capitata is now reserved for the Western Cape species from the Cape Peninsula and nearby. We include these early collections and several more recent collections from the southern coastal mountains in the new species Aristea rufobracteata, naming it for the unusual dry, redbrown spathes.


Introduction
In the course of a review of herbarium collections of Aristea Aiton, we identified specimens of tall plants with hairless, reddish brown inflorescence spathes and bracts from the Langeberg, Outeniqua, Tsitsikamma and Baviaanskloof mountains in South Africa as an undescribed species.These collections were identified as Aristea bakeri Klatt or Aristea capitata (L.) Ker Gawl.[or their synomyms Aristea confusa Goldblatt, Aristea major Andrews or Aristea thyrsiflora (D.Delaroche) N.E.Br.], following Weimarck (1940), who included several early collections of the taxon from the George and Knysna districts of the southern Western Cape in his circumscription of A. capitata.The name A. capitata is now reserved for the Western Cape species from the Cape Peninsula and nearby.We include these early collections and several more recent collections from the southern coastal mountains in the new species Aristea rufobracteata, naming it for the unusual dry, redbrown spathes.
The African and Madagascan genus Aristea, now with some 58 species (Goldblatt & Manning 2013), is the sole genus of the Iridaceae subfamily Aristeoideae Vines (Goldblatt & Manning 2008).Centred in western southern Africa, where it is both most diverse and species rich, the genus has some eight species in Madagascar and 11 in tropical Africa; of these, five are shared with southern Africa and one with Madagascar (Goldblatt & Manning 2013;Goldblatt, Phillipson & Manning 2013).Aristea rufobracteata is a member of subgenus Aristea section Racemosae Weim.This section, which is restricted to the winter rainfall zone of southern Africa (Goldblatt [2012] 2013), is recognised by its robust habit, minutely notched style and three winged, apically dehiscent capsules containing flattened, lamellate seeds.

Research method and design
We examined all relevant collections at the herbaria with significant collections of southern African plants, namely the Bolus Herbarium, University of Cape Town (BOL), Royal Botanic Gardens, Kew (K), the Compton Herbarium, South African National Biodiversity Institute, Cape Town (NBG), the Missouri Botanical Garden, Saint Louis (MO), the National Herbarium, South African National Biodiversity Institute, Pretoria (PRE) and the South African Museum Herbarium, South African National Biodiversity Institute, Cape Town (SAM) (acronyms after Holmgren, Holmgren and Barnett [1990]).We also reviewed the relevant literature and implemented our conclusions with a formal description of the new species.

Distribution
Scattered along the southern coastal mountains of the Western and Eastern Cape, where it has been recorded from the Langeberg between Heidelberg and Riversdale, the Outeniqua Mountains above George, the Tsitsikamma mountains near Clarkson, and the Baviaanskloof Mountains at Loerie (Figure 2).The species occurs on stony sandstone slopes in fynbos, mainly at an altitude from 400 m a.s.l. to 600 m a.s.l., and flowers primarily after fire.

Diagnosis
Aristea rufobracteata is broadly similar to A. capitata in its tall stature, often densely columnar flowering axis and relatively short capsules (11 mm -14 mm long).The flowering stem is branched but the branches are usually fairly short (sometimes up to 150 mm long) and erect or suberect.The individual flower clusters are sessile or subsessile and the inflorescence spathes and floral bracts are rusty brown, thinner and slightly paler toward the margins; the spathes are usually obtuse but are sometimes more or less acute (Figure 3a).
The reddish brown spathes and bracts differ substantially from those of A. capitata, which are pale and silvery translucent, with a dark brown central keel extending upwards as an attenuate, cusp-like tip (Figure 3b).Aristea capitata is centred on the Cape Peninsula, extending eastwards to the Riviersonderend Mountains and northwards to the Piketberg, thus some distance to the west of the nearest station for A. rufobracteata.
Most collections of A. bakeri have a rather open, paniclelike inflorescence with well-developed secondary and sometimes even tertiary branches, which are occasionally suberect.The rust-coloured bracts are usually minutely hairy to scabrid beneath and always have evident, narrow, semitransparent margins.Aristea bakeri extends from the Cape Peninsula in the west to Uitenhage in the east, thus overlapping considerably with A. rufobracteata in the eastern half of its range, and both have been recorded in the mountains above George.
Capsules are particularly important in distinguishing species of section Racemosae (Goldblatt & Manning 1997).Aristea rufobracteata has capsules 11 mm -14 mm long, thus shorter than most collections of A. bakeri, in which they are typically 18 mm -30 mm long.The seeds are lamellate and irregularly kidney shaped, with brown papillae along the margins, like those of A. bakeri and its allies, Aristea juncifolia Baker and Aristea racemosa Baker.The margins of the seeds in A. capitata are smooth.Plants illustrated under the name A. capitata in Curtis's Botanical Magazine (Ker Gawler 1802) are almost certainly A. rufobracteata.The important taxonomic differences amongst the three species are summarised in Table 1.

Conservation notes
Aristea rufobracteata is relatively widely distributed and occurs in several conservation areas.There are no immediate threats.

Source:
Compton Herbarium, South African National Biodiversity Institute, Cape Town Scale bar, 10 mm.
Compton Herbarium, South African National Biodiversity Institute, Cape Town Scale bar, 5 mm.