New species of Euphorbia (Euphorbiaceae) from eastern Ethiopia

New species of Euphorbia (Euphorbiaceae) from eastern Ethiopia

Mats Thulin1

Summary. The new species Euphorbia suborbicularis Thulin, E. kabridarensis Thulin, E. piceoides Thulin and E. michaeliiThulin, from the Somali National Regional State (Ogaden) of Ethiopia, are described and illustrated. E. suborbicularisis probably related to the eastern African E. polyantha, E. kabridarensis is obviously a close relative of E. intricata insouth-eastern Ethiopia, southern Somalia and north-eastern Kenya, E. piceoides is close to E. adjurana in southernEthiopia and northern Kenya, whereas E. michaelii is apparently related to E. xylacantha from northern Somalia andadjacent parts of Ethiopia.

Key Words. Ethiopia, Euphorbia, Euphorbiaceae, new species, Ogaden.

During field work in the Somali National RegionalState (Ogaden) of Ethiopia in May 2006 and February2007 four species of Euphorbia L. were encounteredthat cannot be matched with any previously knowntaxa and that are here described as new species.

Euphorbia suborbicularis Thulin sp. nov. differt ab E.polyanthae Pax caulibus succulentis (non lignosis)albidis (non postremo rubro-brunneis), foliis suborbi-cularibus cordatis (non late obovatis cuneatis) petiolo5 – 15 mm (non 2 – 5 mm) longo, cyathiis stipitatis(non sessilibus), et involucro, ovario, stylis et filamentispubescentibus (non glabris). Typus: Ethiopia, SomaliNational Regional State, Harerge, 34 km from Godealong road to Kelafo, Thulin, Kaariye & Wilhelmi 11302(holotypus ETH; isotypi K, UPS).

Soft-wooded subshrub, c. 0.5 m tall, with stems much-branched and ascending to form tangled masses;stems fleshy, up to 1 cm in diameter, terete, smooth,greyish white with a waxy surface, minutely puberu-lous; leaf scars prominent, becoming black. Leavesalternate, mostly well separated; petiole 5 – 15 mmlong, flattened, minutely puberulous; blade suborbic-ular, 25 – 45 mm long and wide, ± distinctly cordate atthe base, rounded to shallowly emarginate at the apex,glabrous above, minutely puberulous below; stipulesrepresented by minute dark glands. Inflorescence a(1 –) 3-rayed pseudumbel at tips of branchlets, oftenwith additional axillary cymes below, subtended by awhorl of leaf-like bracts; rays 2.5 – 6 cm long, dichasial,slender, often arching, pale green; axillary cymes up to10 cm long, slender, arching, pale green, becoming grey,persistent; paired bracts sessile, reniform-semicircular,

up to 14 × 20 mm, truncate to cordate at the base and ±overlapping, broadly rounded and shortly apiculate atthe apex, glabrous above, minutely puberulous below.Cyathia bisexual, on c. 1 mm long pubescent stipe;involucre cup-shaped, c. 2 × 2 mm, densely pubescentwith spreading hairs; glands 4 or 5, sessile, transverselyelliptic, spreading, c. 0.5 × 1 mm, subentire with theouter margin deflexed and minutely crenulate, green,glabrous above, minutely pubescent below; involucrallobes fan-shaped, c. 1 mm long and wide, withlaciniate margin. Male flowers several; bracteoleslinear with fimbriate tips; pedicels c. 2 mm long;filaments c. 0.6 mm long, pubescent; anther lobesyellow, sessile, ovoid, c. 0.3 mm long. Femaleflowers: ovary pubescent, exserted on pubescentrecurved pedicel; styles c. 2 mm long, spreading,joined at the base, with distinctly 2-fid tips, denselypubescent with spreading hairs. Capsule exserted c.2 mm from involucre on ± recurved pedicel, broadlyellipsoidal, c. 4.5 × 4 mm, greenish with reddishbase, densely pubescent with spreading hairs. Seedsc. 3 × 2 mm, flattened, with raphe on ventral side,pale yellow with scattered whitish tubercles, acute,greyish white at the tip; caruncle white, hairy, easilyfalling off. Fig. 1.

DISTRIBUTION. Euphorbia suborbicularis is known onlyfrom the type locality in the south-eastern part of theSomali National Regional State (previously HarergeRegion) of Ethiopia. Only a few plants of this specieswere seen in the area.SPECIMEN EXAMINED. ETHIOPIA. Somali NationalRegional State, Harerge, 34 km from Gode along roadto Kelafo, 5°46 ′N, 43°50 ′E, 22 May 2006, Thulin, Kaariye& Wilhelmi 11302 (holotype ETH; isotypes K, UPS).

Accepted for publication April 2009.1 Department of Systematic Biology, EBC, Uppsala University, Norbyvägen 18D, SE-752 36, Uppsala, Sweden and Honorary Research Fellow, Royal Botanic

Gardens, Kew, UK. e-mail: [email protected]

KEW BULLETIN VOL. 64: 469–476 (2009)

© The Board of Trustees of the Royal Botanic Gardens, Kew, 2009

Fig. 1. Euphorbia suborbicularis. A portion of plant; B portion of cyme; C fruiting cyathium; D seed, two views. All from Thulin et al.11302. DRAWN BY MARGARET TEBBS.

470 KEW BULLETIN VOL. 64(3)


HABITAT. Open Acacia-Commiphora bushland in a rockygully on gypsum; 300 m. Other woody species in theimmediate surroundings include Boswellia ogadensis,Commiphora oddurensis, Euphorbia ogadenensis, E. polyanthaand Jatropha rivae.VERNACULAR NAME. Ciin (Somali, at the type locality).This name is used also for various other species ofEuphorbia in Somali, such as E. cameronii, E. consobrina,E. nubica and E. gossypina (Carter 1993).CONSERVATION STATUS. This species may well have awider range, but in view of its very restricted knowndistribution and the small number of plants seen, itshould be regarded as Critically Endangered CR D1.However, at present there are no particular threats tothe type locality.NOTES. This is a very distinctive species with somewhatuncertain affinities. Probably it is related to Euphorbiapolyantha Pax in sect. Eremophyton Boiss., a fairlywidespread species in Kenya, Tanzania, Somalia andsouth-eastern Ethiopia, and also found in the typelocality of E. suborbicularis. However, the new speciesdiffers markedly from E. polyantha in, for example, itsfleshy (not distinctly woody), greyish white (not finallyreddish brown) stems, suborbicular and cordate (notbroadly obovate and cuneate) leaves with 5 – 15 mm(not 2 – 5 mm) long petiole, stipitate (not sessile)cyathia, and pubescent (not glabrous) involucre,ovary, styles and filaments. Also the bracts tend to belarger (up to 14 mm versus up to 10 mm long) and therays longer (up to 6 cm versus up to 3 cm long) inE. suborbicularis than in E. polyantha.

Euphorbia kabridarensis Thulin sp. nov. differt ab E.intricatae S. Carter planta majore caulibus juvenibusglabris (non pubescentibus) et cyathiis glandulissuborbicularis (non transverse ellipticis). Typus: Ethio-pia, Somali National Regional State, Harerge, 50 kmNE of Kebri Dehar, Thulin, Kaariye & Wilhelmi 11585(holotypus ETH; isotypi K, UPS).

Slender shrub, c. 2.5 m tall, unarmed; bark on old stemsgreyish brown, transversely flaking; young stems darkgrey or greyish brown, glabrous. Leaves clustered at tipsof branches, leaving prominent scars; blade obovate toelliptic, 10 – 22 × 4 – 12 mm, entire, flat or with slightlyundulate and revolute margin, subacute to rounded orslightly emarginate at the apex, cuneate at the base,minutely pubescent along margins, otherwise glabrous,venation obscure except for prominent ± roundedmidrib below; petiole c. 1 mm long, ciliolate; stipulesminute reddish brown pointed glands. Cyathia bisexual,sessile, solitary at branch tips; bracts obovate-spathulate,1.5 – 2.5 × 1 – 1.5 mm, often apiculate, reddish, ciliolateand otherwise glabrous or sparsely pubescent, deciduous;involucre cup-shaped, 3 – 3.5 × 4.5 – 5 mm including

glands, densely puberulous; glands 5, well separated,subcircular, c. 1.5 mm in diameter, pressed to theinvolucre, green, glabrous above, minutely puberulousbeneath, with minutely crenulated margin; involucrallobes fan-shaped, c. 1.5 mm long and wide, with laciniatemargin. Male flowersmany; bracteoles c. 2mm long, withfeathery tips; pedicels c. 2.5 mm long, puberulous inupper part; filaments c. 1.2 mm long, minutely puber-ulous; anther lobes yellow, sessile, ovoid, c. 0.7 mm long.Female flower: ovary sessile, densely puberulous; styles 3,c. 1.2 mm long, puberulous, joined for c. 0.4 mm at thebase, with spreading flattened shortly bifid tips. Capsulesessile, obtusely 3-lobed, c. 5 × 6 mm, greyish, denselypuberulous. Seeds ovoid, c. 3 × 2.5 mm, pale brown,smooth, without caruncle. Fig. 2A – D.

DISTRIBUTION. Euphorbia kabridarensis is known onlyfrom the type locality NE of Kebri Dehar (Kabridar) inthe eastern part of the Somali National Regional State(previously Harerge Region) of Ethiopia. Only a fewplants of this species were seen in the area.SPECIMEN EXAMINED. ETHIOPIA. Somali NationalRegional State, Harerge, 50 km NE of Kebri Dehar,7°04 ′N, 44°27 ′E, 4 Feb. 2007, Thulin, Kaariye &Wilhelmi 11585 (holotype ETH; isotypes K, UPS).HABITAT. Acacia-Commiphora bushland on rocky hill-side with mixture of sand and rocks; c. 900 m.Associated woody plants in the type locality includeAdenia venenata, Commiphora rostrata, Euphorbia cf.scheffleri, Moringa rivae and Wrightia demartiniana.CONSERVATION STATUS. This species may well have awider range, but in view of its very restricted knowndistribution and the small number of plants seen, itshould be regarded as Critically Endangered CR D1.However, at present there are no particular threats tothe type locality.NOTES. Euphorbia kabridarensis is closely related toE. intricata S. Carter in sect. Lycopsis Boiss., a speciesdistributed in south-eastern Ethiopia, southern Soma-lia and north-eastern Kenya. These two species agreein being unarmed woody plants with leaves withrounded midribs on the underside, solitary andpuberulous cyathia, and puberulous capsules. How-ever, E. kabridarensis is a shrub c. 2.5 m tall withtransversely flaking bark on old stems and glabrousyoung branches (not a tuberous-rooted shrublet to30 cm or rarely 80 cm tall with pubescent stemssometimes peeling at the base), cyathia with almostcircular glands pressed to the involucre (not withtransversely elliptic and spreading glands), and slightlylarger capsules and seeds (c. 5 × 6 and 3 × 2.5 mm,respectively, versus c. 3.5 × 4.5 and 2.5 × 2 mm).

Euphorbia piceoides Thulin sp. nov. differt abE. adjuranae P. R. O. Bally & S. Carter ramis valde

471NEW SPECIES OF EUPHORBIA (EUPHORBIACEAE) FROM EASTERN ETHIOPIA


Fig. 2. A – D Euphorbia kabridarensis (Thulin et al. 11585). A leafy branch; B portion of stem showing flaking bark; C floweringbranch; D fruiting branch. E – G Euphorbia michaelii. E habit (Thulin et al. 11123); F flowering branch (Thulin et al. 11606); G fruitingbranch (Thulin et al. 11604). PHOTOGRAPHS BY MATS THULIN.



arcuatis pendulis non ramificantibus trunco tegenti-bus segmentis 2 – 3 cm (non 5 – 15 cm) longis, spinisusque ad 25 mm (non 15 mm) longas, cymis saepe plusquam 3 (non 1 – 3), cyathiis glandulis contiguis (nonseparatis). Typus: Ethiopia, Somali National RegionalState, Harerge, 7 km NNE of Kelafo, Thulin, Kaariye &Wilhelmi 11329 (holotypus ETH; isotypi K, UPS).

Tree, up to 4 m tall; trunk simple, mostly entirelycovered by the persistent branches, but these maydrop off in old individuals to leave the trunk clear atthe very base; branches unbranched, fleshy, stronglyarched and soon hanging with ascending tips, c. 1 mlong, forming an oblong-conical crown, (4 –) 5-angled, 1.5 – 4 cm wide, distinctly winged, constricted

Fig. 3. Euphorbia piceoides. A habit; B upper portion of branch; C tip of branch, showing cymes; D portion of spine-shield showingbases of spines, leaf scar, prickles, flowering eye with scars of 3 cymes and flanked by minute secondary spines; E cyme; F cyathiumin top view. All from Thulin et al. 11329. DRAWN BY MARGARET TEBBS.



at ± regular intervals into ± rhombic to triangularsegments 2 – 3 cm long, greyish green; angles straightto shallowly and sinuately toothed with teeth 0.5 –1 cm apart. Spine-shields contiguous to form a hornymargin 2 – 3 mm wide; spines 5 – 25 mm long, up to2 mm thick at the base, shorter at the constrictions;prickles up to c. 1 mm long; flowering eye sometimesflanked by a pair of secondary spines 0 – 1 mm long.Leaves deciduous, not seen. Cymes (1 –) 3 – 5 in ahorizontal line, glabrous, once forked, 8 – 15 mmlong, with stout peduncle and ascending branches;paired bracts sessile, rounded, 1.5 – 2 × 2.5 – 3 mm.Cyathia first male only, apparently later bisexual,sessile; involucre cup-shaped, fleshy, c. 5 × 6 mmincluding glands; glands 5, spreading, fleshy, trans-versely elliptic, c. 1.5 × 2.5 mm, yellow; involucral lobesfan-shaped, c. 1.5 mm long and wide, with laciniatemargin. Male flowers numerous; bracteoles deeplylaciniate, 4 – 5 mm long; pedicels 5 – 6 mm long,glabrous; filaments c. 1.2 mm long, glabrous; antherlobes yellow, c. 0.3 mm long. Female flowers and fruitsnot seen. Fig. 3.

DISTRIBUTION. Euphorbia piceoides is known only fromthe type locality in the south-eastern part of the SomaliNational Regional State (previously Harerge Region)of Ethiopia, where some 20 individuals of the specieswere seen.SPECIMEN EXAMINED. ETHIOPIA. Somali NationalRegional State, Harerge, 7 km NNE of Kelafo, 5°40 ′N,44°09 ′E, 24 May 2006, Thulin, Kaariye & Wilhelmi 11329(holotype ETH; isotypes K, UPS).HABITAT. Open Acacia-Commiphora bushland on thetop and slopes of a gypsum hill; c. 320 m.VERNACULAR NAME. Qamadhi (Somali, at type locality).CONSERVATION STATUS. This species may well have awider range, but in view of its very restricted knowndistribution and the small number of plants seen, itshould be regarded as Critically Endangered CR D1.However, at present there are no particular threats tothe type locality.NOTES. Euphorbia piceoides, with its numerous hangingbranches with ascending tips, from a distance muchresembles a Christmas tree. It belongs to subgen.Euphorbia, where its closest relative may be E. adjuranaP. R. O. Bally & S. Carter in southern Ethiopia andnorthern Kenya, a species that in Ethiopia grows atabout 1800 m altitude in Gamu Gofa and SidamoRegions (Gilbert 1995). E. piceoides differs markedlyfrom E. adjurana in habit by its strongly arching andhanging unbranched branches that are long persistentand cover the trunk except sometimes in old individ-uals, where the trunk may be left clear at the very base.In E. adjurana the branches are erect to more or lessspreading, less arched, branched, and tend to fall offto leave a large proportion of the trunk clear.Furthermore, the branches of E. piceoides are more

distinctly segmented with segments 2 – 3 cm (not 5 –15 cm) long, the spines are up to 25 mm (not up to15 mm) long, and the cymes are often more than 3(not 1 – 3) in each flowering eye, and the glands ofthe cyathia are touching (not separated).

Euphorbia michaelii Thulin sp. nov. differt abE. xylacanthae Pax caulibus 15 – 28 mm (non 8 –15 mm) crassis, tuberculis 8 – 12- (non 5-) seriatis, etaculeis 0 – 0.3 mm (non 1 – 3 mm) longis. Typus:Ethiopia, Somali National Regional State, Harerge,along track from Kebri Dehar to Gode, Thulin, Kaariye& Wilhelmi 11606 (holotypus ETH; isotypi K, UPS).

Succulent medusoid perennial with central stem atground level and lateral spreading stems up to 25 cmlong forming dense clumps up to 0.5 m or more indiameter; stems 15 – 28 mm thick, with 8 – 12 ranks ofprominent laterally somewhat compressed tubercles 5 –10 mm apart, pale green. Spine-shields oblong, 5 – 7 ×2.5 – 3 mm, first reddish brown, soon turning whitish;spines solitary, first reddish brown soon turning whitish,15 – 22 mm long, spreading, stout, c. 1.5 mm thick at thebase; prickles 0 – 0.3 mm long. Leaves triangular, fleshy,c. 1.5 × 1.5 mm, soon deciduous. Cymes solitary,1-forked, with stalk and branches becoming pink; stalkup to 6 mm long; branches up to 5 mm long; bractslinear-lanceolate to oblong or ovate, 1.5 – 2 mm long,denticulate at the apex; cyathia bisexual, funnel-shaped,c. 3.4 × 4 mm; glands 5, just touching, almost erect,fleshy, transversely elliptic, 1 – 1.5 × 1.5 – 2 mm, dullreddish or dirty yellow; involucral lobes fan-shaped, c.1.5 mm long and wide, with laciniate margin. Maleflowers numerous; bracteoles linear, c. 3 mm long,fimbriate; pedicels c. 4 mm long, glabrous; filaments c.1 mm long, glabrous; anther lobes c. 0.5 mm long.Female flowers: ovary sessile, glabrous; styles 3, c. 3 mmlong, twisted, joined for c. 1 mm at the base, withexpanded slightly bifid tips, glabrous. Capsule sessile,obtusely 3-lobed, c. 3 × 4 mm, glabrous, pale brown.Seeds ovoid, c. 2.5 × 1.5 mm, pale grey, closely andshallowly tuberculate, without caruncle. Figs 2E – G, 4.

DISTRIBUTION. Euphorbia michaelii is known only from afew, closely situated localities between Kebri Dehar andGode in the south-eastern part of the Somali NationalRegional State (previously Harerge Region) of Ethiopia.SPECIMENS EXAMINED. ETHIOPIA. Somali NationalRegional State, Harerge, 60 km from Kebri Dehar onroad to Gode, c. 30 km NE of Denan, 24 June 1971,Gilbert 2296 (K, cymes in spirit, from a plant cultivatedin Addis Abeba that flowered in Feb. 1972); 51 km ontrack from Kebri Dehar to Gode, 6°36 ′N, 43°57 ′E, 13May 2006, sterile, Thulin, Kaariye & Wilhelmi 11123(ETH, UPS); along track from Kebri Dehar to Gode,6°35 ′N, 43°55 ′E, 5 Feb. 2007, in flower, Thulin, Kaariye



Fig. 4. Euphorbia michaelii. A branch; B spine-shield, showing base of spine, leaf scar, prickles and flowering eye; C cyme;D cyathium; E involucral lobe; F fruiting cyathium; G tip of style; H seed. A, B from Thulin et al. 11335; C – E from Gilbert 2296;F – H from Thulin et al. 11604. DRAWN BY MARGARET TEBBS.



& Wilhelmi 11606 (holotype ETH; isotypes K, UPS);52 km along track from Kebri Dehar to Gode, 6°35 ′N,43°53 ′E, 5 Feb. 2007, in fruit, Thulin, Kaariye &Wilhelmi 11604 (ETH, K, UPS).HABITAT. Locally common in Acacia-Commiphora bush-land, usually in rocky places on gypsum; 550 – 600 m.CONSERVATION STATUS. This species is locally com-mon and good populations were seen in 2006 and2007 also in several other localities close to thosewhere it was collected. However, in view of itsrestricted known area of distribution it should beregarded as Vulnerable VU D1, although at presentthere are no particular threats to any of the localities.NOTES. This distinctive species in subgen. Euphorbiawas treated as “E. sp. = Gilbert 2296” in Flora ofEthiopia and Eritrea (Gilbert 1995), and it is nownamed after its first collector, my friend andcolleague Michael G. Gilbert, Kew. He knew it fromsterile plants seen and photographed in the fieldbetween Kebri Dehar and Gode in 1971, as well asfrom cymes in spirit originating from plants culti-vated in Addis Abeba. The species was found againin the same area in May 2006 when only sterileplants were seen, but flowering and fruiting plantswere collected in February 2007.

Euphorbia michaelii is related to E. xylacantha Pax innorthern Somalia and adjacent parts of Ethiopia(Carter 1993), but differs from this in its thickerstems (15 – 28 mm versus 8 – 15 mm thick), with 8 – 12(not 5) ranks of tubercles and vestigial 0 – 0.3 mm (not1 – 3 mm) long prickles.

AcknowledgementsI am grateful to Friedrich Wilhelmi and Hassan YusufKaariye at the Dibatag Field Research Project of AlWabra Wildlife Preservation (Sheikh Saoud Mohd. BinAli Al-Thani) for assistance in the field, to the SwedishResearch Council for financial support, to MargaretTebbs for the illustrations, and to Mike Gilbert forcomments on the manuscript.

ReferencesCarter, S. (1993). Euphorbia. In: M. Thulin (ed.), Flora of

Somalia 3: 306 – 337. Royal Botanic Gardens, Kew.Gilbert, M. G. (1995). Euphorbia. In: S. Edwards,

Mesfin Tadesse & I. Hedberg (eds), Flora of Ethiopiaand Eritrea 2 (2): 331 – 378. Addis Ababa University& Uppsala University.



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New species of Euphorbia (Euphorbiaceae) from eastern Ethiopia