The Gerire Hills, a SE Ethiopian outpost of the transitional semi-evergreen bushland: vegetation, endemism and three new species, Croton elkerensis (Euphorbiaceae), Gnidia elkerensis (Thymelaeaceae), and Plectranthus spananthus (Lamiaceae) Ib Friis a,b , Michael G. Gilbert b , Alan J. Paton b , Odile Weber c , Paulo van Breugel d and Sebsebe Demissew b,e a Section for Biosystematics, Natural History Museum of Denmark, Copenhagen Ø, Denmark; b The Herbarium, Science Collections Department, Royal Botanic Gardens, Kew, Richmond, Surrey, UK; c Recherche – Sciences de la Vie, Section Botanique, Musée national d’histoire naturelle de Luxembourg, Luxembourg, Luxembourg; d Department for Geo Media & Design, HAS University of Applied Sciences, ‘s-Hertogenbosch, The Netherlands; e The National Herbarium, Department of Plant Biology and Biodiversity Management, Addis Ababa University, Addis Ababa, Ethiopia ABSTRACT The vegetation of the plateaux of the Gerire Hills, of unique geology, represents an outlier of the Transitional semi-evergreen bushland of the eastern escarpment of the Ethiopian high- lands, about 160 km from continuously distributed vegetation of this type. In the lowland surrounding the hills is deciduous Acacia-Commiphora bushland, typical of the Somalia-Masai region. Unpublished data from a 1937 Italian expedition documents past existence of Juniperus procera on the plateaux. Three new narrowly endemic species are described here from recently collected material: Croton elkerensis Friis & M.G. Gilbert (Euphorbiaceae), Gnidia elkerensis Friis & Sebsebe (Thymelaeaceae), and Plectranthus spananthus A.J. Paton, Friis & Sebsebe (Lamiaceae). Three previously described species from the hills, Blepharispermum obovatum Chiov. (Asteraceae), Aloe elkerriana Dioli & T.A.McCoy (Aloaceae) and Euphorbia bertemariae Bisseret & Dioli (Euphorbiaceae), are narrow endemics. The species most similar to the bushland endemics occur in a range of vegetation types and phytochoria in East Africa south of Ethiopia or more widespread in Africa. The species most similar to the succulent endemics occur elsewhere in semi-evergreen bushland on limestone at the mountain range in northern Somalia. The Gerire Hills endemics are considered Vulnerable (VU) or Least Concern (LC) given the differing threats to their respective habitats. ARTICLE HISTORY Received 30 June 2018 Accepted 25 July 2018 KEYWORDS Acacia-Commiphora bushland; Audo Range; conservation; gravitational spreading domain; Somalia-Masai region; taxonomy; Yesomma sandstone Introduction The Gerire Hills are named after a little known ethnic group inhabiting these hills. Their name is also spelt Gherire, Girirra, Gariirre and Garirrä (Banti 2005). The Gerire Hills form a range of mountain crests and plateaux, which are up to 1200–1350 m high and located between the Weyb and the Wabe Shebelle Rivers in the western Ogaden, south-eastern Ethiopia at ca. 6° N, 42° E (Figure 1(A)). The hills form the southern end of the Audo Mountain Range (Mège et al. 2015: Figure 19.2), a mountain range of extraordinary geological significance. Mège deplores ‘that the landscape of the Ogaden and its flora and fauna have not been better studied to date’, due to ‘the remoteness and limited infrastructure but also of the difficult security conditions that have prevailed over large areas for many years’ (Mège et al. 2015, 346). The Gerire Hills are entirely within the former Bale region, BA in the Flora of Ethiopia and Eritrea (Hedberg et al. 1989–2009). On a field trip in 2014, Ib Friis and Sebsebe Demissew visited the Gerire Hills to look for more species of Commiphora and Commicarpus in Acacia- Commiphora bushland. Unexpectedly, the Gerire Hills turned out to be covered by Transitional semi- evergreen bushland (van Breugel et al. 2016), and the trip lead to discovery of three new species (Croton elkerensis Friis & M.G. Gilbert (Euphorbiaceae), Gnidia elkerensis Friis & Sebsebe (Thymelaeaceae) and Plectranthus spanathus A.J. Paton, Friis & Sebsebe (Lamiaceae)), as well as rediscovery of the narrow endemics Blepharispermum obovatum Chiov. (Asteraceae) and sight record of Aloe elkerriana Dioli & T.A. McCoy (Aloaceae), while the second endemic species of Aloe, A. jacksonii Reynolds, was not seen. On a subsequent trip in 2016, staff members at the Ethiopian National Herbarium (ETH) went back to the area to collect more material. The first botanist to collect in the Gerire Hills was Enrico Reghini, who took part in an Italian expedi- tion in 1937. The visit of that expedition resulted in an unpublished and anonymous report on geology, ethnology, agriculture and botany, Cenni monografici sul paese dei Gherire, with 90 typed pages submitted CONTACT Ib Friis ibf@snm.ku.dk Natural History Museum of Denmark, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark WEBBIA https://doi.org/10.1080/00837792.2018.1505379 © 2018 Dipartimento di Biologia, Università di Firenze Published online 03 Sep 2018