New species of Iridaceae from the Hantam-Roggeveld Centre of Endemism, and the Bokkeveld, Northern Cape, South Africa

Three new species o f Iridaceae are described from the Bokkeveld and Roggeveld Escarpments. Ixia amethystina. a member o f section Dichone, is endemic to the edge o f the Roggeveld Escarpment. It shares an unusual, inclined spike that is nodding in bud with I. trifolia but is distinguished by its blackish purple (not yellow) anthers, narrower leaves 1.5-2.0 mm wide, medium-textured corm tunics that form a distinct neck at the base o f the stem, and short style branches 2.0-2.5 mm long. Moraea marginata. another Roggeveld endemic, is a member o f section Polvanthes and florally similar to M. fistulosa and M. monticola but differs in its linear, channelled leaves 5-7 mm wide, with unusual, thickened margins. Romulea singularis. from the edge o f the Kobee River Valley in the Bokkeveld Mountains, is a member o f section Ciliatae. It is unique in the genus in its narrowly funnel-shaped, mauve to purple flowers with slender perianth tube 10-11 mm long, and unusually long filaments, 8 -9 mm long, inserted in the lower half o f the tube.


INTRODUCTION
Plant geographers have been aware of the high levels of endemism in the flora of the winter rainfall region along the western margin of the Upper Karoo for almost a century, culminating in its recent recognition as the Hantam-Roggeveld Centre of Endemism (Van Wyk & Smith 2001).The Hantam-Roggeveld occupies the high-lying southwestern portion of the South African interior plateau and includes the Hantams.Roggeveld and Nuweveld Mountains.The vegetation is primarily succulent karroid shrubland, with renosterveld at the higher elevations and in moister areas.The region is exceptionally rich in geophytes, which may account for nearly 40% of the flora in some places (Snijman & Perry 1987).The richest and most interesting geophyte flora is found along its western rim. on the main Roggeveld Escarpment and on the Hantamsberg.which receives more rain than the surrounding country.Among the geophyte flora are some 90 species of Iridaceae, many endemic to the region (Manning el al. 2002).I he Bokkeveld Mountains, which border the Hantam-Roggeveld in the northwest, constitute the northern limit of the Cape Floral Region (Goldblatt & Manning 2000).This sandstone escarpment supports dry fynbos vegeta tion.with a narrow belt of renosterveld along its interior margin.Although not recognized as a separate centre of endemism by Van Wyk & Smith (2001).the region is a centre of diversity for several geophyte genera (Manning et al. 2002), and its flora includes numerous endemic Iridaceae (Manning & Goldblatt 1997).
Here we describe two new species from the Roggeveld-H an tarn plateau, Ixia amethystina and Moraea margina ta, and a third, Romulea singularis, from the Bokkeveld Mountains.All three species appear to be most closely allied to other endemics from their respective regions, emphasizing the importance of local radiation in the floras of these two regions.Two of these species, M. marginata and R. singularis, were brought to our atten tion by botanist and ardent plant enthusiast.Nick Helme, who has been responsible for the discovery of several new species in the Cape region in the past few years (Manning & Goldblatt 2001a: Van Jaarsveld & Thomas 2003;Goldblatt 2004).
Plants 150-300 mm high.Corms globose, 12-20 mm diam.; tunics of medium-textured.wiry, reticulate Fibres, extending up in papery neck 30-70 mm long.Stem erect, unbranched or with up to two branches that are erect below and then inclined.1.0-1.5 mm diam.below base of main spike.Cataphylls submembranous.flushed reddish brown, upper one reaching above ground level and then papery and dark reddish brown.Leaves 3 or 4. all basal, uppermost completely sheathing lower two thirds of stem, remainder suberect or lowermost slightly falcate.1.5-2.0mm wide, reaching to near top of stem, firm-textured.margins and midrib hyaline, slightly thickened, plane or slightly twisted in upper half, with an additional one or two membranous, scale-like leaves in upper third of stem, in axils of which lateral branches may develop.Spike inclined, crowded.5-7-flowered.branches 1 -4-flowered.inflorescences nodding in bud: bracts scarious, translucent or flushed purple above.
outer 5-7 mm long, acute or obscurely three-dentate, inner bracts about as long as outer or slightly shorter, bicuspidate, margins connate in lower 1.5 mm around ovary.Flowers rotate, pale purple with small, dark purple eye, faintly scented; perianth tube filiform and clasping style for entire length, 2 .0-2.5 mm long, widened only in upper 1 mm; tepals obovate, somewhat narrowed below into short claw, spreading and slightly cucullate distally, 12-13 x 7-8 mm.Filaments inserted at apex of tube and occluding throat, blackish purple, free, diverging above, 2.5 mm long; anthers oblong-sagittate, 4.5-5.0x 1.5 mm, erect, thecae narrowly separated by connective and dehiscing laterally by narrow slits extending length of thecae, blackish purple; pollen creamy yellow.Ovary' ovoid, 2.5-3.0 mm long; style straight and erect, ± 2 mm long, dividing at or just below mouth of tube, branches involute-filiform and stigmatic at apex only, purple, arching outward, 2.0-2.5 mm long.Flowering time: late September to early October.Figure 1A-F.
Distribution and ecology: Ixia amethvstina is known from a small area southwest of Middelpos on the edge of the Roggeveld Escarpment (Figure 2).The three known collections were made within a few kilometres of each other on the Farms Zoekop and Agterkop.Plants grow in stony clay in renosterveld (Elvtropappus rhinocerotis) Diagnosis and relationships: Ixia amethystina is an attractive species distinguished by its pale purple flowers with small, dark eye, relatively broad, blackish anthers that dehisce laterally so that the pollen forms a contrasting pale margin to each anther, and short style branches that are subequal to the filaments in length, thus scarcely projecting from between the stamens.The lovely amethyst-coloured flowers are borne on inclined spikes so that they face directly upward in an elegant, arching spray.
The filiform perianth tube clasping the style for its whole length and the involute-filiform style branches stigmatic only at the extreme apex, place Ixia amethys tina in section Dichone of subgenus Ixia (Goldblatt & Manning 1999).Here it falls among a small group of spe cies that are endemic or near-endemic to the Roggeveld Escarpment, including I. brevituba G.J.Lewis, I. trifolia G.J.Lewis and I. cu n ata G.J.Lewis.These species share relatively unspecialized, longitudinally dehiscent anthers.4-5 mm long.The species of section Dichone from the southwestern Cape below the Escarpment, in contrast, fall into two groups defined by their derived stamens, the one characterized by its very short anthers, 2-4 mm long and the other by their curious attachment, resulting in their reclinate orientation.
Among the Roggeveld species of section Dichone, Ixia amethystina appears to be most closely allied to /. trifolia (Figure 1G.H) on the basis of their unusual, inclined spikes, and lateral branches that arc decurved and nodding when young.All other species have spikes that arc erect from bud to fruit.Although not explicitly mentioned in the original description of I. trifolia (Lewis 1962), this feature was later noticed and illustrated by De Vos (1999).The two species both have a perianth tube 2-3 mm long, which is longer than in I. brevituba (1.0-1.5 mm) but shorter than in I. curvata (3-5 mm).I. amethystina differs from I. trifolia in its blackish purple anthers, purple perianth tube, which gives the flowers a small, dark, central eye, consistently narrower leaves 1.5-2.0mm wide, and medium-textured corm tunics drawn into a well-developed neck.I. trifolia, like all other species in section Dichone, has yellow anthers, although the filaments may be pale mauve, and a pale perianth tube, giving the flowers a well-defined, whit ish eye.The observation by Lewis (1962) and later De Vos (1999) that I. trifolia may occasionally have a dark eye is not corroborated by examination of living plants.The pale eye in this species is usually surrounded by darker shading, which in pressed specimens may give the eye a dark appearance.The leaves of I. trifolia are broader than in I. amethystina.(2.5-)5.0-12.0mm wide, and the tunics are more coarsely fibrous, with the lower fibres developed into woody claws but not drawn into a neck above.In addition, the style branches in I. trifolia are longer than the filaments.4-5 mm long, and project conspicuously betw een them.
The unusual pale purple of the flowers o f Ixia amethystina occurs occasionally in both I. trifolia and I. brevituba (Lewis 1962) although the flowers in these two species are more usually bright pink.Other species of section Dichone invariably have pale to deep pink flowers.I. trifolia is more widely distributed along the Roggeveld Escarpment than I. amethystina and has been collected from several places along the escarpment from Uitkvk in the north to Komsberg in the south and thence to Laingsburg and Tweedside below the escarpment.The two species are parapatric, with I. amethystina occur ring immediately to the north of the range of I. trifolia.The differences in their flowers appear to be related to their pollination biology.I. amethystina has flowers that conform to the hopliine beetle pollination syndrome (Goldblatt et al. 1998) and the beetle Kubousia axillaris Burmeister has been collected on the flowers.All indi viduals of this insect carried pure loads of Ixia-type pol len on their dorsal thorax and frons (unpublished data).In contrast.I. trifolia is pollinated by solitary female anthophorine bees (unpublished observations).

Other material examined
Ecology, known from a single small population on the southern outskirts of the town of Sutherland at an eleva tion of around 1 550 m (Figure 2).Plants occur locally in fine alluvium over shale at the foot of outcrops of sandstone in open, succulent karroid scrub.The leaves are quite dry and withered at flowering, and the attrac tive, blue-violet flowers, 20-25 mm in diameter, open in early summer in the late afternoon for just a few hours, withering around sunset.
Diagnosis and relationships'.Moraea marginata is recognized by the combination of stellate, purplish flowers with free stamens and filiform style branches, and a solitary, linear, channelled leaf with conspicuous, maroon margins that are conspicuously thickened when dry.The distinctive flower form places M. marginata with the two species previously segregated as the genus Roggeveldia.This genus was established by Goldblatt (1979) for R.fistulosa Goldblatt, a Moraea-hke plant that was anomalous in Moraea as then circumscribed in hav ing free stamens and filiform style branches that spread between the stamens, rather than being opposite to and ± appressed to them as in typical species of Moraea.A second species of Roggeveldia, R. montana Goldblatt, very similar to R.fistulosa in morphology, was described by Goldblatt (1992) more than a decade later.At this time he suggested that the relationships of the genus lay with Moraea section Polyanthes, most particularly with M. crispa Thunb., with which it shared a similar vegetative and floral morphology, including a rotate, blue-violet perianth, free stamens and narrow style branches without style crests.The genus Roggeveldia was subsequently included in Moraea sect.Polyanthes (Goldblatt 1998), following a revision of the circumscription of Moraea.Initially based on evidence from morphology, anatomy and chromosome cytology, this decision received sub sequent support from molecular study (Goldblatt et al. 2002b).
Moraea marginata is indistinguishable from M. fistulosa (Goldblatt) Goldblatt (= Roggeveldia fistulosa) and M. monticola Goldblatt (= R. montana) in its flowers but differs sharply from them in its vegetative morphology.M. fistulosa is characterized by an erect, fistulose leaf about as tall as the stem and up to 3 mm in diameter, whereas the smaller M. monticola is distinguished by its trailing, filiform leaf, longer than the stem and twisted and slightly coiled, and ± 1 mm in diameter.In both these species, therefore, the leaf is terete/filiform.M. margi nata is thus unique in the group in its linear, channelled leaf, 5-7 mm wide, with conspicuously thickened and cartilaginous margin.The leaf of M. marginata, which is longer than the stem, trailing, and slightly twisted and coiled, represents a remarkable specialization in the M. crispa alliance.Similar leaves with thickened margins are also encountered in some plants of M. crispa from the Roggeveld Plateau, including Bond 145 (NBG, SAM) from the Farm Gunstfontein on the Klein Roggeveld, and Snijman 774 (NBG) from near Williston.Although these collections are vegetatively indistinguishable from M. marginata, the partially fused filaments and flattened style branches, bifid at the tips and with small style crests, are entirely consistent with M. crispa and there is no doubt that they represent that species.
All the species of the Roggeveldia group have a simi lar phenology, flowering in early summer, in October or November, with individual flowers opening in the late afternoon around 16:00 and withering in the evening between 19:00 and 20:00.The species are concentrated in the western Karoo, along the edge of the central escarpment, and are generally poorly known and col lected.Moraea marginata and M. fistulosa are known only from the type collections, both from the edge of the Roggeveld Escarpment near Sutherland, and M. mon ticola from three collections, one in Namaqualand and two from the southern margin of the Great Karoo.M. crispa, in contrast, is widespread through the drier inte rior mountains of the Cape region and along the western and southern edge of the interior escarpment (Goldblatt 1986).M. crispa is probably plesiomorphic in its some what flattened and bifid style branches and thus most likely sister to the Roggeveldia-group.
Ecology : known from a single population on the Bokkeveld Escarpment near Nieuwoudtville.on the east ern edge of the Kobee River Gorge in the Oorlogskloof Nature Reserve.The plants are rare and localized in seasonally wet sand and moss on sandstone pavement in arid fynbos vegetation.At the time that the species was collected in mid-September, most of the plants had finished flowering, suggesting that peak flowering takes place in early September.
Diagnosis and relationships: although known from just two plants, the flowers of Romulea singularis are so unusual that they leave no doubt that the species is dis tinct.R. singularis is readily distinguished from all other species by its narrowly funnel-shaped, mauve to purple flowers with slender perianth tube, 10-11 mm long.The unusually long filaments, 8-9 mm long and puberulous at the base, are inserted in the lower part of the tube and are shortly exserted, and the floral bracts are short, 8-10 mm long.The unusual length of the filaments and their insertion in the lower part of the tube, at the top of the basal, narrow portion, are unique among the handful of long-tubed species of Romulea that are known (Manning & Goldblatt 2001b).Those with a truly salver-shaped flower [R.alba J.C.Manning & Goldblatt, R. hantamensis (Diels) Goldblatt, R. stellata M.P.de Vos and R. syringodeoflora M.P.de Vos] have the filaments inserted near the mouth of the tube, but even R. kamisensis M.P.de Vos, with a narrowly funnel-shaped flower, has the fila ments inserted in the upper part of the tube.In addition, the filaments in all of these species are glabrous through out and 3-5 mm in length, thus not unusually long.
The oblique corm with crescent-shaped basal ridge splitting into parallel fibrils, places Romulea singularis in section Ciliatae of subgenus Romulea (Manning & Goldblatt 2001b).Within the section, however, its rela tionships are more difficult to determine.The narrowly funnel-shaped, mauve to purple flower at first appearance suggests an atypically short-tubed form of R. kamisensis M.P.de Vos, a species that is thus far known from central Namaqualand and the northern rim of the Knersvlakte.Closer examination, however, reveals that the resem blance is superficial.The bracts of R. kamisensis are much longer, 13-22 mm long, and the filaments, which are inserted in the upper part of the tube, are entirely glabrous, just 4-5 mm long, and are included within the tube.In all these respects R. kamisensis is quite unlike R. singularis and it is therefore probable that the similarity in flower form in the two species is convergent.
The unusually well-developed, basal ridge on the corm, with the parallel fibrils grouped into small clus ters, may suggest a possible relationship with Romulea toximontana M.P.de Vos.This species, which is also endemic to seasonally wet sandstone pavement on the Bokkeveld-Matsikamma-Gifberg Mountain complex, is distinctive in section Ciliatae in the wide, fan-shaped basal ridge on the corm.Its white, cup-shaped flowers, with short perianth tube, although quite unlike those of R. singularis in shape, share with it the darker streaks in the throat and the pale yellow anthers, and the bracts are typically short, 10-20 mm long, with similar slender veins.Unfortunately these features are probably all plesiomorphic and it is therefore only the well-developed rim on the corm that might actually signal a relationship between the two species.Cytology may prove more useful since the chromosome number, In = 28, in R. toximontana is unique in section Ciliate, where 2n = 24 is usual (DeVos 1972).
On the basis o f the presence of secondary vascular bun dles in the leaves, and possibly also their shared chromo some number, 2n = 26, which is rare in section Ciliatae, it is likely that the long-tubed Romulea kamisensis shares a short-tubed ancestor with R. namaquensis M.P.de Vos (Manning & Goldblatt 2001b).R. singularis may be similarly but independently derived from some other short-tubed species and it does appear as if most o f the long-tubed species o f Romulea are independently derived within the genus in response to pollination by longtongued insects.The pollination biology of the genus has been fairly well studied (Goldblatt et al. 2002a), and most o f the other long-tubed species have been shown to be adapted to pollination by long-proboscid flies in the family Ncmestrinidae.A similar pollination system is thus likely for R. singularis, and the species will most probably prove to be another member o f the Prosoeca peringueyi pollination guild, which is well-developed in the Bokkeveld Mountains (Manning & Goldblatt 1996).
Etymology: named for its unusual flowers.