Two new subspecies of Dietes ( Iridaceae : Iridoideae ) , Dietes iridioides subsp . angolensis from Angola and Dietes bicolor subsp . armeniaca from eastern South Africa , with notes and range extensions for Dietes butcheriana and Dietes iridioides

Results: Two new subspecies in Dietes are described, viz. Dietes iridioides subsp. angolensis from Angola, constituting the first record of the species from that country, and Dietes bicolor subsp. armeniaca from eastern South Africa, which represents a range extension into southern KwaZulu-Natal. We also document a range extension for the local endemic Dietes butcheriana from KwaZulu-Natal into the Eastern Cape and discuss an anomalous population of D. iridioides, with long-lived flowers, from near Hankey in the Eastern Cape.


Introduction
With five species in sub-Saharan Africa and one on Lord Howe Island (Australasia), Dietes Salisb.ex Klatt has one of the more remarkable distributions for Iridaceae, in which large disjunctions at generic rank are rare.Of the African species, four are relatively narrow endemics restricted to southern Africa.The fifth, Dietes iridioides (L.) Sweet ex Klatt, however, is widely distributed through eastern southern Africa, from the Riviersonderend Mountains in the Western Cape to Kenya and Uganda (Goldblatt 1981).Here we report substantial range extensions for Dietes butcheriana Gerstner, previously endemic to KwaZulu-Natal but now recorded from Pondoland in the Eastern Cape, Dietes bicolor (Steud.)Sweet ex Klatt, previously known from East London to Grahamstown but now recorded as far north as southern KwaZulu-Natal, and an important new country record for D. iridioides in Angola.Lastly, we discuss a novel variant from near Hankey in the Eastern Cape, South Africa, which we provisionally refer to D. iridioides.Three species of the genus, D. bicolor, Dietes grandiflora N.E.Br.and D. iridioides, are widely cultivated in parts of the world where the climate is suitable, both in gardens and in street and park plantings.They are valued for their drought resistance, tolerance of a range of growing conditions and, with the exception of D. iridioides, their attractive flowers produced over an unusually long time.

Research method and design
We examined all relevant herbarium collections at the primary southern African herbaria, namely the Bolus Herbarium, University of Cape Town (BOL), the Compton Herbarium, South African National Biodiversity Institute, Cape Town (NBG), 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 & Barnett 1990).Plants were also examined alive, either in cultivation at the Kirstenbosch National Botanical Garden or in the field wherever possible.

Results
1. Dietes bicolor (Steud.)Sweet ex Klatt: Records of the species available to Goldblatt (1981) were from a limited area of the Eastern Cape, extending eastwards from near Grahamstown to the mouth of the Kei River in southern Transkei.New collections since then from eastern Transkei in the Mkhambathi Nature Reserve, along the Nyameni River, and from Umtamvuna in southern KwaZulu-Natal just across the Eastern Cape border, extend the known range of this species some 200 km to the north-east.The three northern stations are from a stretch of coast, some 60 km in extent, along the Msikaba, Nyameni [MnYameni] and Umtamvuna rivers.The species should thus also be looked for along the Mtentu River, which lies between the Msikaba and Nyameni.The habitat of D. bicolor is unusual for Dietes.Plants always grow close to water and all three new records are from populations growing along or in the riverbed in situations that are seasonally inundated.
The northern populations appear typical for the species except for details of the flowers.In typical D. bicolor the flowers are a pale lemon-yellow, with small or large dark brown, semicircular blotches at the base of the limb of the outer tepals, the claws of which are minutely dotted with brown (Figure 1a).In the eastern populations, flowers are paler in colour, white to creamy white with orange markings, with diffuse edges at the base of the outer tepal limbs, the claws spotted with orange (Figure 1b).Although the outer tepal claws were described as unmarked by Duncan (2008), his photographs indicate spotting, as in the collections that we examined.This colour variant, collected along the Mzamba River in Pondoland, was accorded cultivar status as 'Mzamba River' by Duncan (2008), but has not been documented in herbaria.Recent new collections extend the known range of this variant, which we recognise as a distinct subspecies.

Distribution
Extending from southern KwaZulu-Natal to the Mkhambathi Gorge in the northern coastal part of the Eastern Cape (Figure 2).A record from Town Bush Valley, Pietermaritzburg, probably does not represent a native population.Subsp.bicolor occurs well to the south and has been recorded from near the mouth of the Kei River southward to Grahamstown (Figure 2), thus some 150 km distant from the nearest recorded station for subsp.armeniaca.Further collecting may narrow that distance.

Diagnosis
Recognised immediately by the white to palest yellow flowers with orange nectar guides and orange-spotted outer tepal claws, but also by the somewhat smaller ( 33  21 mm -29 mm vs 30 mm -35 mm × 20 mm -31 mm) and anthers (4.5 mm -6 mm long vs 6 mm -9 mm long in subsp.bicolor) (Figure 1b, Table 1).The ovary and capsules in subsp.armeniaca are also slightly shorter than in subsp.bicolor.Flowers of subsp.bicolor are pale yellow and the outer tepal limbs show solid, dark brown nectar guides (rarely brownspeckled) and brown-spotted claws (Figure 1a).Gerstner: The eastern southern African D. butcheriana is recognised by its very broad, sword-shaped leaves, seldom less than 25 mm and up to 50 mm wide in healthy, mature plants, and by the large, broadly ovoidoblong capsules of 25 mm -35 mm × approximately 20 mm, which are nodding or pendent at maturity.The capsules do not dehisce, except near the apex, and remain attached to the flowering stems for months after ripening so that plants are seldom without capsules in some stage of development.Seeds are shed after gradual disintegration of the capsule walls (Goldblatt 1981).The relatively small flowers are white, with yellow and orange markings at the base of the limb and along the claw of the outer tepals.The outer tepals are up to 30 mm long and 13 mm at the widest, and the inner tepals are somewhat shorter.The style branches are also white, not pale to deep violet as in the related D. grandiflora and also often in D. iridioides, and are relatively short (approximately 7 mm long), with crests of approximately 5 mm long.The flowers are not often seen, because they open late in the afternoon and fade early in the evening, but the plants are readily identified by their wide leaves and large capsules.

Dietes butcheriana
First recorded in Zululand (Gerstner 1943), D. butcheriana was understood by Goldblatt (1981) to be restricted to  3. Dietes iridioides (L.) Sweet ex Klatt: This is the most widespread species of the genus, extending from forested valleys of the Riviersonderend Mountains in the Western Cape, South Africa, northward through wooded habitats in eastern southern Africa, Mozambique and Zimbabwe into Tanzania, Kenya and Uganda.The species occurs in shady habitats under bush or in evergreen forest.Leaves are typically linear to narrowly sword shaped, 6 mm -15 mm wide and almost as long as the stems, which reach 20 cm -60 cm in height.Flowers are predominantly white, apart from the style branches, which are usually pale violet (rarely white).The outer tepals have yellow markings at the limb bases and rows of brown spots along the claws.The inner tepals are unmarked.The flowers last about eight hours, opening in the late morning and fading and collapsing in the late afternoon.This is similar to other species of Dietes, in which flowers also last just one day, except for D. grandiflora, in which blooms last three days.
A population of plants from tropical thicket near Hankey in the Eastern Cape presents an unusual combination of characteristics.Vegetatively the plants resemble D. iridioides in height and leaf width, and also in the production of small fans of leaves at the tips of old flowering stalks, capable of rooting when reaching the ground as a means of vegetative reproduction.This feature is common in D. iridioides but less so in the related and taller D. grandiflora.The Hankey plants also resemble D. iridioides in their smaller flowers and in the rostrate capsules, but differ from that species in the longlived flowers, which open at about midday to early afternoon (12:00-13:00) and last through the night and into the following day, with the tepals collapsing only from mid morning to early afternoon.The style branches are consistently violet and the inner tepals, which remain suberect, either are uniformly white or have lines of dark brown dots in the lower half.The outer tepals also have unusually wide claws (10 mm wide), narrowing abruptly only at the base, much as in D. grandiflora.
Outer tepals of other collections of D. iridioides have the claws tapering almost uniformly from the apex to the narrow base.Thus, floral longevity, tepal markings and the shape (but not the size) of the outer tepal claw are closer to the largerflowered D. grandiflora than to D. iridioides (Table 2).
The conjunction of vegetative characteristics of D. iridioides with some floral characteristics of D. grandiflora makes us question the status of the Hankey population.Does it merit recognition as an infraspecific taxon and if so, of D. iridioides or D. grandiflora?Or might it be a separate species?We may, presumably, rule out the possibility of it being a hybrid, as the nearest known station for D. grandiflora is near Grahamstown, which is some 180 km east of Hankey.Provisionally, we conclude that it is best to include the Hankey population in D. iridioides.We also note that the habitat (shade under relatively dense thicket) differs from that for typical D. iridioides, which, according to our experience and herbarium records, is found in evergreen forest or woodland under relatively mesic conditions and often along streams.

Diagnosis
We refer the Angolan population to D. iridioides but note several significant differences, which provide the basis for recognition at subspecies rank.The leaves, generally 25 mm -30 mm wide, are significantly wider than in subsp.iridioides, in which leaves are usually 6 mm -15 mm wide, rarely wider in some populations from the KwaZulu-Natal Drakensberg.Notably, our sampling of collections of D. iridioides from Zambia and Congo, the locations nearest to the Angolan station, have leaves quite typical of the species (10 mm -18 mm wide).Flowers of the Angolan plants are predominantly white with faint markings on the outer tepals, which are 22 mm -27 mm long, and have minutely papillate claws.In typical D. iridioides, the outer tepals are 25 mm -35 mm long, the claws are densely hairy and the style branches are usually pale violet but sometimes white.

FIGURE 1 :
FIGURE 1: Diagrammatic representation of Dietes bicolor flowers and detached outer tepals showing variation in shape, size and markings (a) for subsp.bicolor, from a garden plant, and (b) subsp.armeniaca, based on the Abbott 9381 specimen.

FIGURE 3 :
FIGURE 3: Map showing the geographic distribution of Dietes butcheriana.12°3 4°3 3°3 2°3 1°3 0°2 9°2 8°2 7°2 6°2 5°2 4°2 3°2 2°2 1°2 0°1 9°1 8°1 7°1 Figueiredo and Smith (2008).iridioides, with flowers that last only one day, in the nearby Baviaanskloof and in the Gamtoos River lowlands, makes the Hankey population appear all the more intriguing.The flowers are smaller than usual for D. iridioides (Table2) and are almost uniformly white, with faint, dull yellow bilobed arcs at the bases of the outer tepal limbs and light, yellow-brown submarginal lines along the claw margins.The channelled outer tepal claws are minutely papillate (smooth to the naked eye), unlike those in typical D. iridioides, which have a broad, densely velvety, hairy, raised ridge along the midline.The style branches and crests (approximately 6 mm and 4 mm -5 mm long, respectively) of the Angolan plants are only faintly suffused with violet and are smaller than encountered elsewhere in the species.The Angolan plants are clearly closely allied to eastern and southern African D. iridioides, but they seem sufficiently different to us to merit taxonomic recognition at the level of subspecies.Until now, no species of Dietes has been recorded in Angola and the genus is listed neither byFigueiredo and Smith (2008)nor in the online checklist 'Flora of Angola Online' (http://flan.sanbi.org., version as of September 2011).

TABLE 2 :
Comparison of important taxonomic features in Dietes grandiflora and Dietes iridioides.DistributionKnown only from the forest floor on the flanks of Mt.Mocu, the highest peak in Angola.The population may have been more extensive, but logging and forest clearing have destroyed suitable habitat at lower elevations.