Euphorbia venefica Trémaux ex Kotschy (Euphorbiaceae) and other shrub-like cylindrically stemmed Euphorbia with spirally arranged single spines Weber, Odile; Atinafe, Ergua ; Awas, Tesfaye ; Friis, Ib Published in: Societe des Naturalistes Luxembourgeois. Bulletin Publication date: 2020 Document version Publisher's PDF, also known as Version of record Document license: CC BY-NC-ND Citation for published version (APA): Weber, O., Atinafe, E., Awas, T., & Friis, I. (2020). Euphorbia venefica Trémaux ex Kotschy (Euphorbiaceae) and other shrub-like cylindrically stemmed Euphorbia with spirally arranged single spines. Societe des Naturalistes Luxembourgeois. Bulletin, 122, 57-82. https://www.snl.lu/publications/bulletin/SNL_2020_122_057_082.pdf Download date: 24. sep.. 2021 Euphorbia venefica Trémaux ex Kotschy (Euphorbiaceae) and other shrub-like cylindrically stemmed Euphorbia with spirally arranged single spines Odile Weber1, Ergua Atinafe2, Tesfaye Awas3 & Ib Friis4 1 Musée national d’histoire naturelle, 25 rue Munster, L–2160 Luxembourg ([email protected]) 2 Gullele Botanic Garden, P.O. Box 153/1029, Addis Ababa, Ethiopia ([email protected]) 3 Ethiopian Biodiversity Institute, P.O. Box 30726, Addis Ababa, Ethiopia ([email protected]) 4 Natural History Museum of Denmark, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark ([email protected]) Weber, O., Ergua Atinafe, Tesfaye Awas & I. Friis, 2020. Euphorbia venefica Trémaux ex Kotschy (Euphorbiaceae) and other shrub-like cylindrically stemmed Euphorbia with spi- rally arranged single spines. Bulletin de la Société des naturalistes luxembourgeois 122 : 57-82. Published online 15 July 2020 (ISSN 2716-750X). Abstract. On two independent field trips in 2015 and 2018, the authors collected a tall shrub- like succulent species of Euphorbia (Euphorbiaceae) in Combretum-Terminalia woodland of the Omo Valley in south-western Ethiopia. These collections represent the easternmost records of E. venefica Trémaux ex Kotschy and are the first records from inside the borders of Ethiopia. Euphorbia venefica belongs to a group of large succulent species with single spines borne on a spine-shield and arranged on the cylindrical stem in a spiral. The spe- cies in this group are reviewed here, based on material in herbaria and the literature. The East African E. venefica and the West African E. unispina share potential distribution, have overlapping variation in stem- and leaf-morphology and cannot be separated by the charac- ters mentioned in the literature. We consider these two taxa to be one species, to be called E. venefica and distributed from Burkina Faso to Ethiopia. E. poissonii presents characters that may justify it being a separate species restricted to Africa west of Cameroon. Euphorbia darbandensis N.E. Br. and E. sapinii De Wild. are too poorly known and could not be placed. Conservation assessments suggest that neither E. venefica, nor E. poissonii are threatened. Key words. Environmental modelling, nomenclature, Sudanian zone, taxonomy woodland. 1. Introduction lands in south-western Ethiopia, not know- ing of Tesfaye Awas’ find. Here, near the In August 2015, Tesfaye Awas explored the work site of the Omo/Gibe IV dam, Weber northern slopes of the Omo Valley in the observed and collected a shrubby and suc- Konta special woreda, in south-western Ethiopia. This remote area could previously culent c. 2 m tall plant (Fig. 2, 3), which was only be reached on foot or horseback but profusely flowering and fruiting and clearly had become accessible by car because of the belonged to the genus Euphorbia. Using the work beginning on the new Omo/Gibe IV Flora of Ethiopia and Eritrea (Gilbert 1995), dam. Near the Omo River and above the pro- it was possible to assign the plant to subgenus jected dam, he collected and photographed Euphorbia, which counts 45 species out of a sterile, shrubby and succulent plant which the total of 106 species in the Flora account. could not be identified at the time (Fig. 1). It was tentatively identified as E. venenifica In October 2018, Weber, Ergua Atinafe and (for the correct name of this species, see 3.2), Friis went on a field trip to the same general though the geographical information in the area to record the floristic composition of Flora did not support that idea (see 3.1). The the Sudanian woodlands and wooded grass- identification was subsequently confirmed Bull. Soc. Nat. luxemb. 122 (2020) 57 Fig. 1. Detail (above) and general habit (below) of the sterile record of Euphorbia venefica, col- lected as Tesfaye Awas 2627 (ETH). These plants were observed in rather dense woodland in the valley of a small tributary to the Omo River. (Tesfaye Awas phot.) as E. venefica Kotschy at the Royal Botanic sampling and falls under section Euphorbia Gardens, Kew (K). In the most recent phy- (as ‘E. venenifica’) (Dorsey et al. 2013). logenetic study and classification of subge- The field-work by Weber, Ergua Atinafe nus Euphorbia, the species is included in the and Friis was part of a project started by 58 Bull. Soc. Nat. luxemb. 122 (2020) Fig. 2. Detail and general habit of the flowering and fruiting record of Euphorbia venefica, collected as Friis, Weber, Ergua Atinafe & Ermias Getachew 15889 (ETH). These plants were observed in relatively open Combretum-Termi- nalia woodlands just north of the Omo River in Ethiopia. Note the clusters of fruits at the end of several branches in the lower images. (Odile Weber phot.) Bull. Soc. Nat. luxemb. 122 (2020) 59 Friis in 2014 to study the little known flo- Garden (BR; http://www.botanicalcollec- ristic patterns in the woodlands of Ethiopia tions.be/#/en/search). Tropicos (https:// along the borders with Sudan and South www.tropicos.org/) of the Missouri Botani- Sudan (Pichi Sermolli 1957; Harrison & cal Garden, St. Louis, Missouri, USA (MO) Jackson 1958; White 1983; Friis et al. 2010; was consulted for supplementary material. Breugel et al. 2016). Euphorbia venefica has Material of the relevant species seen and not been observed in any of the 152 sites identified is listed in 3.4 and mapped in Fig. studied for this woodland project (for the 5, 7 and 9; imperfect specimens that could study sites between Jimma and the Omo not be satisfactorily identified have been River, see Fig. 4). omitted. In August 2019, Prof. Sebsebe Demissew, Standard methods were used for collecting Addis Ababa, told Weber and Friis about botanical material on our field trips, includ- Tesfaye Awas’ unidentified plant, which they ing the use of GPS. Our post facto georef- immediately realised was the same as the erencing of the 19th century material from flowering succulent plant they had found the Sudan and South Sudan is based on the and identified. The present paper contains a relevant old literature with localities traced joint report on the discoveries, and a critical on the digitised set of maps of Sudan in review of the earlier eastern African collec- 1:250.000 kept at Library of Congress, Wash- tions of E. venefica and of the nomenclature, ington, DC (https://www.loc.gov/resource/ taxonomy and phytogeographical status of g8310m.gct00289/?sp=32), Russeger’s Karte this and related species. The new record is von Ost Sudan, 1843 (https://www.oldmap- of particular interest because the plant has sonline.org/map/cuni/1084712) and the not previously been found so far to the east information in Wickens (1972) and Friis & in Africa. Vollesen (2005). Material from other coun- tries was georeferenced for Cameroon with the use of Letouzey (1968), for the area of 2. Materials and Methods the Flore d’Afrique Centrale with the use of Bamps (1982), for the area of the Flora of All material collected on the field trips in Tropical East Africa with the use of Polhill August 2015 and October 2018 is deposited (1988) and for specimens from elsewhere at the National Herbarium of Ethiopia at with the Fuzzy Gazetteer (http://dma.jrc. Addis Ababa University (ETH). As the col- it/fuzzyg/query/) and Google Earth Pro lections from 2018 could not be satisfacto- (2019). When a collection was indicated to rily identified there, it was sent on loan to have been made between two georeferenced the Herbarium at the Royal Botanic Gar- points, our input in the process of mapping dens, Kew (K). Additional material at K and and modelling is the coordinates of the top- the Natural History Museum, London (BM), ographically most likely site between the two including material in alcohol, has been seen points, estimated in relation to features iden- for this study, both material of the species tifiable in Google Earth Pro (2019). Doubt- with cylindrical stems and spirally arranged fully georeferenced collecting localities cited single spines and material of potentially in 3.4 are marked with ‘[?]’ and not mapped. related species. Herbarium material from The topographical data was converted to other European herbaria has been consulted shapefiles with the software DIVA-GIS 7.5 by correspondence with curators (W and B) (http://www.diva-gis.org/). Modelling of and on digital images traced via the Global the potential distribution has been done Biodiversity Information Facility (GBIF.org with two different methods to secure reli- 2019), Global Plants on Jstor (https://plants. able results: DIVA-GIS, using the BioClim jstor.org/), the Naturalis collections database option, to determine the environmental (http://bioportal.naturalis.nl/), the database envelopes, and MaxEnt 3.4.1 (http://biodi- of the Musée national d’histoire naturelle, versityinformatics.amnh.org/open_source/ Paris (P; https://science.mnhn.fr/institu- maxent/) to model a probability distribution tion/mnhn/collection/p/item/search) and based on grid cells, where the predicted suit- the virtual herbarium of the Meise Botanic ability of conditions for the species is deter- 60 Bull. Soc. Nat. luxemb. 122 (2020) mined for each grid cell.