A new species of Berkheya (Asteraceae, Arctotideae) from the Northern Cape, South Africa

Copyright: © 2014. The Authors. Licensee: AOSIS OpenJournals. This work is licensed under the Creative Commons Attribution License. Background: Berkheya is a large, mainly southern African genus of approximately 75 species, several of which are poorly known and under-collected. Since revision in 1959, only a few new species have been described. Publication of new taxa facilitates conservation objectives and contributes to a better understanding of the southern African flora.


Introduction
Berkheya Ehrh. (Asteraceae) is the largest genus in Arctotideae subtribe Gorteriinae, the 'spiny daisies' of southern Africa. The genus has been shown to be paraphyletic using both molecular (Funk & Chan 2008;Funk, Chan & Keeley 2004) and morphological data (Karis 2006) and changes in generic circumscriptions in the subtribe are anticipated (Karis et al. 2009). Based on current evidence, Berkheya consists of approximately 75 species distributed predominantly in South Africa. The genus was last revised by Roessler (1959) and has thus not been treated as a whole for over 50 years, despite several useful regional treatments, including Goldblatt and Manning (2000), Hilliard (1977), Manning and Goldblatt (2012a) and Snijman (2013), and the description of a handful of new species (Hilliard 1977;Hilliard & Burtt 1975;Manning et al. 2010;Manning & Goldblatt 2012b). The prevalent covering of sharp spines makes Berkheya species difficult and painful to collect and the genus is poorly known and under-collected, despite forming a prominent component of many plant communities.
Berkheya species occur in several bioregions but are concentrated in the Greater Cape Floristic Region, where they are most strongly associated with the winter-rainfall desert (succulent Karoo) vegetation (Verboom et al. in press). Most species are perennial herbs, less commonly shrubs, distinguished from allied genera by the possession of, (1) involucral bracts that are always spiny and basally connate but never hardened into a woody structure, (2) a honeycombed receptacle with the cypselas embedded in alveoli that are all of equal size and (3) a pappus (Roessler 1959). Roessler (1959) divided Berkheya into eight series based on characters of the receptacle alveolar margins, cypsela hair type, pappus arrangement and structure, degree of connation of the involucral bracts, leaf morphology (including degree of division, margin serration and indumentum), leaf arrangement (opposite versus alternate), presence or absence of ray florets and growth form. Additional characters used to define species include hairiness of the stems and leaves, leaf shape and size, form of the leaf margins, size and structure of the leaf spines, arrangement and size of the capitula, ray floret colour and the size and morphology of the involucral bracts.
Berkheya material from a localised area in the northern Bokkeveld escarpment in the Calvinia region of the Northern Cape Province (Figure 1) was examined and this could be distinguished from other species in the genus by its tall, shrubby habit, relatively large and broad leaves, small radiate heads clustered in paniculate groups, very short uniseriate pappus scales and short hairs on the cypselas. This material represents a new species which is described in detail here.

Research method and design
Berkheya specimens from the South African National Biodiversity Institute's (SANBI) Compton Herbarium in Cape Town (NBG), SANBI's South African Museum Herbarium in Cape Town (SAM) and the Bolus Herbarium at the University of Cape Town (BOL) were compared with those of the new taxon. Holotype material was collected and dried using standard techniques in October 2013. Type material has been deposited in NBG, BOL and SANBI's National Herbarium in Pretoria (PRE), Kew Herbarium at the Kew Royal Botanic Gardens, United Kingdom (K) and the Swedish Museum of Natural History Herbarium in Stockholm (S).
Habitat and habit were documented in the field. Morphological structures were examined on dried and rehydrated specimens using a dissecting microscope. Images were captured from the microscopes using an Olympus SC30 digital camera attachment and the software Analysis getIT v. 5.1 (Olympus Soft Imaging Systems, Münster, Germany). Measurements were made on digital images using MeasureIT v. 5.1 from the same company.

Distribution and habitat
This large, shrubby species has been collected from only one locality in the northern Bokkeveld, north-west of Nieuwoudtville, on the very edge of the escarpment (Figure 1). Two subpopulations, each of approximately 30 plants, have been found growing about 800 m apart on steep, southwest-facing slopes amongst large sandstone boulders (Figure 2a). The plants occasionally sprawl over the rocky outcrops. The aspect appears to be important because B. dumicola was not seen in otherwise similar habitats along the escarpment edge which generally have a drier, more northerly aspect.

Ecology
The species grows in tall, fire-protected thicket vegetation. It is estimated that the habitat has not burnt for at least 80 years. The plants are rooted in deep loamy soils and, because of the steep slope and dense surrounding vegetation, are often partly shaded for part of the day. The thicket vegetation in which they occur includes species such as Kiggelaria africana L., Gymnosporia buxifolia (L.) Szyszyl., Lobostemon glaucophyllus (Jacq.) H.Buek., Stachys sp., Podalyria myrtifolia (Retz.) Willd. and Diospyros austroafricana De Winter. Average annual rainfall in the area is likely to be in the order of 400 mm -500 mm per year, with pronounced and rapid declines to the east and west of the escarpment edge (Manning & Goldblatt 1997).

Etymology
The specific epithet 'dumicola' means 'thicket dweller' (Stearn 1967) and refers to the rocky, fire-protected vegetation in which this species occurs.

Diagnosis and relationships
Berkheya dumicola is an unusually large, shrubby species in a genus dominated by perennial herbs. The shrubby habit, radiate heads and relatively broad leaves (Figure 2b) are most consistent with Berkheya series Fruticosae Roessler, but members of this series are characterised by entire or shortly toothed (rarely fringed) receptacle alveolar margins, densely hairy cypselae with the silky hairs often long (up to 4 mm), and a biseriate pappus of lanceolate or subulate scales. The conspicuously fimbriate, serratetoothed alveolar margins, shortly pubescent cypselae with twin-hairs and uniseriate pappus of short, obtuse scales (Figures 3d-3f) Roessler's (1959) series Rigidae, the species of which are characterised by similar alveole, pappus and cypsela characters, as well as sharing anther and pollen features. Species in series Rigidae, however, are generally herbaceous or suffruticose and lack ray florets. Berkheya chrysanthemoides, and now B. dumicola, therefore represent unusually large and radiate putative members of this series. It is remarkable that these likely sister-species, both only recently discovered, occur relatively nearby on the Bokkeveld escarpment. Both species are known from only a single locality each and further collections are required to determine their full geographical ranges and morphological variation.

Conservation status
The total global population of B. dumicola is currently thought to be less than 100 mature plants and the species thus fits the criteria for EN D1 (

Discussion
Berkheya dumicola is morphologically most similar to B. chrysanthemoides and together they form an unusual and geographically proximate subgroup within Berkheya (B. chrysanthemoides is also from the Bokkeveld plateau, growing in the Oorlogskloof Nature Reserve approximately 50 km to the south of where B. dumicola occurs). Of consideration is the fact that both species are known from only very few specimens, so the documented range of within-species variation is small. However, many species do occur naturally in very geographically restricted ranges and with only a small number of individuals. Assessment of natural variation in these cases must, of necessity, be based on a small number of specimens. Careful comparison of morphological differences between B. chrysanthemoides and B. dumicola revealed a suite of characters, derived from both reproductive and vegetative structures, differing sufficiently and consistently to warrant separating the two taxa.

Conclusion
Berkheya dumicola is a new, possibly endangered species recently discovered in the northern part of the Bokkeveld plateau in the Northern Cape Province of South Africa.