Taxonomy of the genus Ehrharta (Poaceae) in southern Africa: the Setacea group

The Setacea species group in the genus Ehrharta Thunb. is differentiated morphologically by the short first sterile lemma and by inflorescences of fewer than 20 spikelets. The Setacea group is composed of two species, each with subspecies linked by intraspecific intermediates: E. rupestris Nees ex Trin. subsp. rupestris; subsp. tricostata (Stapf) Gibbs Russell; subsp. dodii (Stapf) Gibbs Russell and E. setacea Nees subsp. setacea; subsp. scabra (Stapf) Gibbs Russell; subsp. uniflora (Burch, ex Stapf) Gibbs Russell; subsp. disticha Gibbs Russell. All taxa are endemic to the Fynbos vegetation of the south-western Cape Province, with distribution centred in the Caledon degree grid (3419). Parallel trends for plant size and habit, leaf blade width and position, and spikelet size are demonstrated in both species, with similar plant types occurring in similar geographical areas.


INTRODUCTION
The genus Ehrharta in Africa comprises 35 species and infraspecific taxa, and has been divided into seven species groups by correlating many characters of spikelet morphology and leaf blade anatomy, as outlined by Gibbs Russell & Ellis (1987). The leaf blade anatomy in Ehrharta shows a wide range of variation. Characters that normally separate groups at subfamily level else where in Poaceae are here used to distinguish species groups. A detailed treatment of variation within each species and species group is therefore called for. Ellis (1987) demonstrates the variation and discusses the sig nificance of leaf anatomy in the Setacea species group. This paper presents the taxonomy of the species in the Setacea group, and places the morphology of the taxa in context with the anatomy, and with the geographical distribution. The other species groups will be similarly treated in parallel papers in the future.
The seven species groups in Ehrharta may be classi fied into two major categories, those with the first and second sterile lemmas similar to each other and different from the fertile lemma (28 species and infraspecific taxa, in six species groups), and those with the first sterile lemma reduced and glume-like, and the fertile lemma similar to the second sterile lemma (seven species and infraspecific taxa in one species group, the Setacea group, Figure 1). In addition, only in the Setacea group is the number of spikelets always fewer than 20 per inflo rescence. Ellis (1987) has distinguished the Setacea group anatomically by the presence of arm cells in the mesophyll (a character normally of significance at sub family level in grass classification), the shape of the microhairs, the silica bodies and the intercostal long cells. Detailed morphological and anatomical descrip tions of the Setacea group are given by Gibbs Russell & Ellis (1987). Within what is now regarded as the Setacea group, Nees (1841) recognized two species, and the fundamen tal difference of their spikelet plan from that of the rest of the genus was demonstrated by Steudel (1853). Stapf (1900) added three new species and a variety, but Gibbs Russell (1984) placed all of Stapf s taxa, plus an additio nal one, as subspecies within Nees's original two species. These decisions, based on macromorphology and spikelet morphology, are generally supported by anatomical studies (Ellis 1987). In most cases, anatomi cal characters have allowed better interpretation of con fusing morphological states; in other cases, morphologi cal and anatomical evidence do not agree. Some of the variation in the Setacea group, where morphological and anatomical characters are contradictory, may be a result of convergent adaptations for tough, long-lived leaves often encountered in plants of the low-nutrient Fynbos soils.
In Africa, Ehrharta is a genus characteristic of the winter rainfall areas, and has its centre of diversity in Fynbos, but a number of species also occur in Succulent Karoo, Karoo, Savanna and Forest. Six of the species groups have taxa in more than one vegetation type. The Setacea group is unique in being restricted to Fynbos, and occurs only from the Cape Peninsula north to Worcester and east to Humansdorp. Erect or trailing tufted perennial with long creeping rhizomes, of widely varying size and habit, from delicate herbaceous plants 100 mm tall to robust suffrutescent plants 450 mm tall. Culms erect or decumbent, branched and creeping at base, leafless below. Leaves with blades erect or spreading, inrolled, folded or flat; ligule a membrane fringed with hairs; sheaths overlapping. Inflorescence an erect raceme overtopping leaves. Spike lets 1-9, erect, often distichous. Glumes about l A length of entire spikelet, lower ones with tip truncate or rounded, upper ones acute. Florets with sterile lemmas dissimilar, the first sterile lemma a thin scale with 3-5 raised nerves, Yi-l A the length of second, often appear ing to be a third glume; the second sterile lemma hard and thickened, with 7 minutely tubercled nerves, tip canoe-shaped; fertile lemma similar to second sterile lemma, but slightly shorter, broader and with more acute tip. Stamens 6.
The folded leaf blades with hooded tips and the very broad spikelets separate this subspecies from all other taxa in the Setacea group. In spite of these morphologi cal differences, anatomical characters support the combi nation of subsp. rupestris and subsp. tricostata under the same species (Ellis 1987).
The distribution of subsp. rupestris is shown in Figure  2. It is never common. It is most abundant and appears in its typical form in the Riviersonderend Mountains of the Caledon area. From there it extends northward and eastward, over the Langeberg at the Clock Peaks, and out along the dry Klein and Groot Swartberg, where the plants are smaller. In both the Caledon area and in the Klein Swartberg, where subsp. rupestris is sympatric with subsp. tricostata, intermediates in leaf and spikelet characters occur between the two subspecies.
The subspecies grows on mountain slopes among rocks at altitudes of 910 to 1 970 m. Flowering occurs from October to January.
A particularly robust specimen otherwise typical of the subspecies (Van Breda 4436) was collected on coastal sand in the Vanrhynsdorp region, well outside the usual distribution of the subspecies, and in a different habitat. Nevertheless, the anatomical characters closely resemble those of other examples of subsp. rupestris (Ellis 1987). There is some doubt about the correctness of the label of this specimen and its locality has not been plotted on Figure 2. A parallel example is known from E. calycina, in a different species group, where an extremely robust plant over 2 m tall was collected on coastal sand near Lambert's Bay (Gibbs Russell 5615).
In its size, erect habit, and relative abundance, this subspecies is similar to E. setacea subsp. setacea but it may be distinguished by the leaves at the base of the culm. E. rupestris subsp. tricostata has blade-bearing leaves nearly to the culm base, whereas E. setacea subsp. setacea has scale-like, overlapping, bladeless sheaths on the lower part of the culms.
The distribution of subsp. tricostata is shown in Fugure 3. It is the most common and the most wide spread of all seven taxa in the Setacea group, extending from the mountains of the Peninsula north to the Hex River Mountains, and eastward to the Klein Swartberg and along the Outeniqua and Tsitsikama coastal ranges nearly to Humansdorp. The subspecies is not recorded from the Langeberg. Plants from the Peninsula and Cale don are the most robust and erect, with reduced seta ceous leaf blades; plants from the easternmost end of the range are small and fine, although with suffrutescent culm bases; plants from the Hex River Mountains merge into subsp. dodii and are decumbent, herbaceous and have flat leaf blades. All these forms grade gradually into each other. In addition, intermediates link this subspecies with the other two, which might be considered extreme forms. It is clear on anatomical grounds (Ellis 1987) that the smaller form of subsp. tri costata from the eastern part of the range is distinct from the small subsp. dodii, even though they overlap in size.
The subspecies grows in wet places on mountain slopes and at the base of cliffs, at altitudes of 300-2 030 m. Flowering extends from October to February, with most plants flowering in November and December.  Differs from subsp. tricostata mainly in size, habit and in number of spikelets. Plants are less than 250 mm tall, trailing or rarely erect, and rhizomes, culms, and leaves are herbaceous and delicate, with the culms freely branched and the leaf blades inrolled and held erect. Inflorescence of \^\ spikelets, 5-10 mm long, barely overtopping leaves. Spikelets 4,5-5 mm long, to 2 mm across above glumes.
This subspecies is difficult to distinguish except on glume length from the two small, delicate subspecies of E. setacea. In general, E. rupestris subsp. dodii is trail ing or erect, with erect rolled leaf blades, whereas E. setacea subsp. uniflora is also trailing, but usually has flat leaf blades, and E. setacea subsp. disticha is erect with spreading, rolled or folded leaf blades. However, in each taxon the habit is variable to some extent.
The distribution of subsp. dodii is shown in Figure 4. It has the most restricted range of any subspecies of E. rupestris, occurring only from Constantia Berg on the Peninsua around to Kogelberg, and northward through Hottentots Holland and Franschhoek to the Hex River Mountains. It is connected in the eastern part of its range to subsp. tricostata by intermediates of slightly larger stature, upright habit and with more numerous spikelets. These occur within the range of typical subsp. dodii as well as to the east as far as Montagu. The lax Hex River Mountain form of subsp. tricostata should perhaps be counted among these intermediates.
The subspecies grows in wet places on mountainsides among rocks and at the bases of cliffs, at altitudes of 660-1 660 m. Flowering occurs from November to early January.
Erect or trailing tufted perennials with long creeping rhizomes, sometimes stoloniferous, of widely varying size and habit, from delicate herbaceous plants 100 mm tall to robust suffrutescent plants 600 mm tall. Culms decumbent or prostrate, suffrutescent or herbaceous, often leafless below. Leaves with blades erect, recurved or spreading, inrolled, folded or flat; ligule a membrane fringed with hairs; sheaths overlapping. Inflorescence an erect raceme barely to considerably overtopping leaves. Spikelets 1-15, at first erect but spreading at anthesis. Glumes % (very rarely only l A) as long as to longer than lemmas, both acute. Florets as in E. rupestris.
Plant erect, 250-400 mm tall. Culms suffrutescent, branched near base, bare of leaves below, sometimes with much shortened inflated side branches. Leaves with blades hard, smooth, usually tightly inrolled and appear ing setaceous, straight and erect or curved outward and spreading from the middle, 50-80 (110) X 4 mm; sheaths overlapping at upper intemodes, basal sheaths without leaves, yellowish, truncate, slightly spreading. Inflorescence of 5-15 spikelets, 25-60 mm long, usually overtopping leaves by at least its own length. Spikelets 5,5-6,8 mm long, oblong; glumes % as long as, to longer than spikelet, not gaping at maturity. This subspecies is most similar in habit and size to E. rupestris subsp. tricostata, but that taxon has blade-bear ing sheaths at the lowest culm nodes, while E. setacea subsp. setacea has conspicuous pale, bladeless, squaretopped sheaths at the lower nodes of the culm. Leaf anatomical features (Ellis 1987) suggest that the two taxa might be united. However, each is linked by interme diates to different but parallel lines of morphological variation. The anatomical similarity, which extends even to species in unrelated genera, is an example of conver gence in leaf characters common in Fynbos. It is note worthy that the two taxa with this typical 'Fynbos ana tomy' are the most widespread subspecies in the Setacea group.
The distribution of subsp. setacea is shown in Figure  5. It is the western element of E. setacea, and is the most widespread of the four subspecies, occurring from the Cape Peninsula north to Baines Kloof and east only as far as the Hottentots Holland and Kogelberg Mountains. In the Klein Rivier Mountains and at Betty's Bay in the Caledon District it is linked to subsp. uniflora and subsp. disticha by intermediates of smaller size and semi-herba ceous habit.

Ehrharta setacea N ees var. scabra Stapf: 669 (1900). Type: Cape, in a mountain peak near Swellendam, Swellendam D i\.,B u r c h e ll 7312 (K ,h o lo .!; PRE, photo.!).
Plant erect, 250-600 mm tall, stoloniferous. Culms suffrutescent, branched near base, sometimes with much shortened side branches. Leaves with blades scabrous, flat at base, rolled near tip, held 45° from culm at sheath, to 30-110 x 6 mm; sheaths overlapping. Inflorescence of 5-17 spikelets, 30-55 mm long, overtopping leaves by at least twice its own length. Spikelets (6,5) 7-8 mm long, oblong; glumes 2 A -Y* as long as lemmas, not gap ing at maturity. This subspecies is easily distinguished from all other African Ehrharta species by the scabrous leaf blades, with a texture resembling that of a Melica or a Leersia. Anatomically, subsp. scabra and subsp. setacea differ considerably (Ellis 1987), raising the question whether they should be treated as separate species. Despite their anatomical differences and the absence of intermediates between the two allopatric entities, they were kept as subspecies because of the confused situation in the Cale don area, where intermediates occur between subsp. setacea and subsp. scabra to both subsp. uniflora and subsp. disticha.
The distribution of subsp. scabra is shown in Figure  6. It occurs only along the Langeberg from the Clock Peaks above Swellendam to Garcia's Pass, and thus forms the eastern element of E. setacea. In the Caledon area, it is linked through a number of intermediates to subsp. disticha and subsp. uniflora.
The subspecies grows mostly in disturbed places on mountainsides, such as path sides and burned clearings, and also among rocks in seepage areas, at altitudes of 350-1 212 m. Flowering occurs from October to January and sporadically to March. Plants sprawling or trailing, delicate but forming dense masses. Culms fine, herbaceous, freely branched, lowest nodes bearing leaves with blades. Leaves not dis tichous, blades soft, flat, straight, 50-80 X 2 mm; sheaths barely or not overlapping. Inflorescence of \-A spikelets, 5-14 mm long, barely overtopping leaves. Spikelets 4,5-6,5 mm long; glumes usually slightly longer than lemmas but sometimes slightly shorter, gap ing more than 45° at maturity. This subspecies can be distinguished from the other two small taxa in the Setacea group by its long glumes (E. rupestris subsp. dodii has short glumes) or trailing habit (E. setacea subsp. disticha is erect).
The distribution of subsp. uniflora is shown in Figure  7. It is known only around False Bay, from the Cape Peninsula to Pringle Bay. In the Caledon District inter mediates occur to subsp. setacea and subsp. scabra.
The subspecies grows in seepage areas, marshy places and along watercourses, as well as at forest margins. It is the only taxon in the Setacea group to occur at low alti tudes, from 10-500 m. Flowering occurs from Septem ber to December, and occasionally to March.  Plant erect, cushion-forming, to 250 mm tall, differ ing from subsp. scabra mainly in size, number of spike lets and position of glumes. Culms branched near base, suffrutescent, lowest nodes usually leafless. Leaves dis tichous, blades hard, rolled, recurved or erect, to 30 mm long. Inflorescences of 1 or 2 spikelets, 5-10 mm long, barely overtopping leaves. Spikelets 4-5 mm long; glumes slightly shorter than lemmas, gaping more than 45° at maturity. This small subspecies is separated from short-glumed E. rupestris subsp. dodii by its long glumes, and from lax E. setacea subsp. uniflora by its erect habit and generally smaller spikelets with glumes slightly shorter than the spikelet.
The distribution of subsp. disticha is shown in Figure  8. It is known only from the Babylon's Tower and Klein River Mountains of the Caledon area. A number of inter mediate specimens show that in this area it intergrades with subsp. setacea and subsp. scabra.
The subspecies grows in dry rocky places on mountain slopes, at altitudes of 580-1 225 m. All other taxa in the Setacea group grow in damp or wet places. The striking habit difference between subsp. disticha and subsp. uni flora may result from adaptation of the former to water stress in a dry habitat. Flowering occurs in October and November. distinctive distribution. Only one subspecies occurs throughout the range of the group, E. rupestris subsp. tricostata. The other subspecies show vicariant distribu tion, limited to particular mountain ranges.
Although they are very similar, the seven infraspecific taxa recognized here are each distinguished by macro morphological, spikelet and anatomical differences. The occurrence of intermediates links them into two groups with parallel morphological trends, as shown in Table 1. These two groups are treated as separate species, with the linked entities which they comprise treated as sub species. In each species, the most widespread and com monly collected subspecies is a robust plant with hard setaceous leaves: E. rupestris subsp. tricostata and E. setacea subsp. setacea. Each species has a robust subspecies of more restricted eastern distribution differ entiated from the widespread one by broader spreading leaf blades and larger spikelets: E. rupestris subsp. rupestris and E. setacea subsp. scabra. Each species has little delicate subspecies with reduced inflorescences and small spikelets in the Peninsula and Caledon area: E. rupestris subsp. dodii, E. setacea subsp. uniflora and E. setacea subsp. disticha. Each of these reduced taxa has a distinctive habitat. E. rupestris subsp. dodii grows in wet places at high altitudes, E. setacea subsp. uniflora grows in wet places at low altitudes, and E. setacea subsp. disticha grows in dry places at high altitudes. Thus, the factors in the Caledon area that favour small size are apparently independent of moisture regime and altitude.

CONCLUSION
The Setacea group is composed of very closely related taxa, as shown by both morphological and anatomical characters. These taxa are distinguished from other Ehrharta species by the spikelet plan, with a short first sterile lemma, and by a number of anatomical features. These distinctive characteristics indicate that the Setacea group must be carefully reviewed when generic limits in the Ehrharteae are examined. The Setacea group has a more restricted distribution than any other group in the genus. All the subspecies except E. setacea subsp. sca bra occur in the Caledon degree grid (3419), and exam ples of all the intermediates also occur in this degree grid. Thus, the Setacea group is concentrated in the south-western phytogeographical centre of Weimarck (1941) and the smaller south-western centre of Oliver et al. (1983). Outside this pivotal area, each taxon has a AKNOWLEDGEMENTS I thank: the Directors of herbaria that have lent speci mens, Bolus Herbarium (BOL), University of Cape Town; Moss Herbarium (J), University of the Witwatersrand, Johannesburg; Wicht Herbarium (J[F), Jonkershoek Forestry Research Centre; The Herbarium, Royal Bo tanic Gardens, Kew (K); National Botanic Garden, Kirstenbosch (NBG & SAM); Botanical Research Unit, Stellenbosch (STE). Also R. P. Ellis and W. D. Clayton for profitable discussions, G. Condy for the spikelet drawing, and especially W. Roux for technical assis tance and preparation o f diagrams.