Abstract
Background: The African genus Schistostephium has eight species in southern and south tropical Africa. The most widely distributed species, Schistostephium crataegifolium, occurs in upland or montane areas towards the eastern side of the continent.
Objectives: The objective of this study was to document a new geographic distribution record of this species from the Bié Plateau of central Angola.
Method: Specimens of S. crataegifolium were collected near Chitembo, Bié Province, during fieldwork for the Future Okavango Project grant 01LL0912A, task SP05, a project aimed at providing scientific support for sustainable land and resource management of the Okavango basin of Angola, Namibia and Botswana. The specimen was identified at the Herbarium of the Royal Botanic Gardens, Kew, UK.
Results: The collection represents a new generic record for Angola, which is disjunct from the nearest population in Katanga by approximately 1000 km.
Conclusion: New generic records such as this underline the need for basic botanical inventories in the large, ecologically diverse but poorly documented country of Angola.
Introduction
The African genus Schistostephium Less. (Lessing 1832:251) was revised by Harris (2012), who recognised eight species. Five of these have restricted distributions in South Africa and Swaziland, but three species are recorded from tropical Africa. Schistostephium oxylobum S. Moore (1911:117) occurs in the eastern Highlands of Zimbabwe and neighbouring Mozambique, and Schistostephium heptalobum Oliv. & Hiern (Oliver & Hiern 1877:399) is found in southern Zambia, northern and eastern Zimbabwe and central Mozambique. Schistostephium crataegifolium (DC.) Fenzl ex Harv. (De Candolle 1838:134; Harvey 1865:169) is by far the most widely distributed species in the genus and ranges from southern Tanzania and the Katanga region of the Democratic Republic of Congo through to the Eastern Cape Province of South Africa. However, neither this species nor indeed the genus has been recorded from Angola, Botswana or Namibia (Figueiredo, Beentje & Ortíz 2008; Harris 2012; Setshogo 2005).
Schistostephium can be distinguished from related genera in the subtribe Cotulinae Kitt by its four-lobed rather than five-lobed corollas. All species are herbs or shrubs, and specific delimitation relies on vegetative characters, on the shape and size of the capitulum and the number of florets. Schistostephium crataegifolium has deeply dissected leaves distributed along the main stem and relatively small, non-cylindrical capitula.
Research method and materials
Material
The specimen was collected in May 2013, during fieldwork in the Cusseque core site for the Future Okavango Project, in one central 100 m2 subplot of a 20 m × 50 m plot (Felfili, Carvalho & Haidar 2005). The other two records were collected in a general walking survey method (Filgueiras et al. 1994). Fertile material was collected and prepared using traditional botanical methods (Fish 1999; Victor et al. 2004). A set of duplicate specimens was prepared and sent to Kew Herbarium, where the specimen was determined.
Procedure
The collection was identified in consultation with the author of the recent taxonomic revision of Schistostephium, applying the characters listed in that work, and by comparison of the material with herbarium collections at Kew, British Museum of Natural History (BM) and electronic resources available through JStor Plants and the LISC online catalogue. The specimen was mounted and labelled in LUBA, the barcode was created from collector number and printed in Zebra Printer (TLP 2844), the digitalisation was done in a Scan Epson (10000 XL), following JStor protocols, and the resultant image was saved in standardised format.
Ethical considerations
Permits
Collection of biological materials in Angola is not currently regulated by specific legislation. The project during which the material was collected comes under the framework of a bilateral agreement between Angola, represented by the Instituto Superior de Ciências de Educação da Huíla (ISCED – Huíla) in Lubango, and Germany, represented by the University of Hamburg (UHH). Transfer of biological material to Kew was approved by Provincial Department of Agriculture, Fisheries and Environment. All International Conventions, to which Angola is signatory, such as Convention on International Trade in Endangered Species of Wild Fauna and Flora (1973), Convention on Biological Diversity (1992), International Treaty on Plant Genetic Resources for Food and Agriculture (2004), and all other national and international relevant instruments concerning biodiversity were taken into consideration.
Taxonomic treatment
Schistostephium crataegifolium (DC.) Fenzl ex Harv. Compositae. In: W.H. Harvey & O.W. Sonder, Flora Capensis 3: 169 (1865). Basionym: Tanacetum crataegifolium DC.: 134 (1838).
Type: SOUTH AFRICA. [Eastern Cape Province], between Grahamstown and Blue Krantz, 08 Sept. 1813, Burchell 3619 (G-DC lectotype, designated by Harris (2012:108), K001044982! isolectotype).
Description (adapted from Harris 2012)
Erect woody herb or small shrub to 1.2 m with striate pubescent stems. Leaves distributed along the main stem, alternate, sessile or shortly petiolate, blade variably pinnatisectly divided, often with two or three orders of branching, pubescent on both surfaces. Capitula solitary or in branched clusters, involucre broadly and shallowly campanulate, (4–)6 mm – 8 mm diameter; phyllaries c. 30, multiseriate and subequal but apex and margins of inner phyllaries becoming more hyaline; receptacle broadly domed and hollow. Florets: outermost florets female, 5 or fewer (often absent), corolla yellow, tube 1.6 mm – 2.3 mm long, glabrous, lobes 0.2 mm – 0.4 mm long, acute and slightly inturned, style drying yellow. Cypselas of female florets flattened and winged, c. 0.8 mm × 0.6 mm; pappus absent. Inner florets hermaphrodite, 30–60(–110), corolla yellow, tube c. 1.5 mm long, lobes 0.3 mm – 0.4 mm long, acute and slightly inturned forming a hood, outer surface of lobe apex with granular yellow glands; anthers yellow, c. 0.8 mm long, anther appendages acute or rounded, base acute, anther collar pigmented. Cypselas of hermaphrodite florets c. 1.3 mm long, sometimes glandular, innermost achenes sometimes with apparently unicellular setulae on inner angle; pappus absent.
Distribution and ecology
Schistostephium crataegifolium occurs from the Eastern Cape of South Africa through to southern Tanzania and the Katanga region of the Democratic Republic of Congo, mostly following the more upland or montane regions towards the eastern side of the continent. The new record represents a westward disjunction of around 1000 km from Katanga (Democratic Republic of Congo) to the Bié Plateau of central Angola (Figure 1), where it occurs at moderate altitude (c. 1560 m) in an area with mean annual precipitation of around 1000 mm per year (Gröngröft et al. 2013; Weber 2013). Two other records were made by a team member in the study area (13.699870 S, 17. 074210 E) and close by Comuna do Mumbué (13.931679 S, 197102 E). The area where the species was collected is covered in moist miombo woodland dominated by Brachystegia spp., Julbernardia paniculata and Cryptosepalum exfoliatum subsp. pseudotaxus (Barbosa 1970; Revermann & Finckh 2013; Revermann et al. 2013; Figure 2).
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FIGURE 1: Location of the Okavango basin in southern Africa and the Cusseque core site denoted in red, where Schistostephium crataegifolium was collected. |
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FIGURE 2: Open woodlands in Cusseque area, Bié Plateau, where the species was collected, dominated by Brachystegia spp., Julbernardia paniculata and Cryptosepalum exfoliatum subsp. pseudotaxus. |
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New record
ANGOLA. Bié Province: Cusseque study area, Chitembo, 13.70056 S, 17.05258 E, 14 May 2013, Maiato FM971 (K!, LUBA!) (Figures 3 and 4).
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FIGURE 3: Digitised image of Schistostephium crataegifolium (DC.) Fenzl ex Harv. |
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FIGURE 4: Schistostephium crataegifolium (DC.) Fenzl ex Harv. as found in the Cusseque study area. |
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Conclusion
This new generic record for Angola is a reflection of the uneven collecting activity and consequent inadequacies in the documentation of the flora of this large and ecologically diverse country. Despite the relatively recent publication of a national checklist of vascular plants (Figueiredo & Smith 2008), field surveys in several parts of the country conducted by the last author (D.J.G.) and colleagues have added over 70 species to this list and many potentially new species. All botanical inventories undertaken by this author in Angola over the last 5 years have resulted in new records for the country or for regions within it.
Acknowledgements
F.M.P.G. is extremely grateful to BMBF (Federal Ministry of Education and Research) for providing financial support for this study through the Future Okavango Project. The authors thank Rasmus Revermann for providing the map of the study area additional species records and photo of species. The authors also thank the traditional authorities of Cusseque village, local communities and field guides. D.J.G. also thanks D.J. Nicholas Hind and Tim Harris at Kew for their specialist knowledge of Schistostephium.
Competing interests
The authors declare that they have no financial or personal relationships which may have inappropriately influenced them in writing this manuscript.
Authors’ contributions
F.M.P.G. conducted the fieldwork during which the new record was collected and co-wrote the account with the other two authors. J.J.T. performed all the herbarium work, including the digitalisation of the specimen for the manuscript and D.J.G. identified the specimen duplicate and contributed towards writing the manuscript. The authors contributed equally during the revision process of the manuscript.
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