Nord. J. Bot. - Section of tropical taxonomy

Euphorbia applanata sp. nov. (Euphorbiaceae) from Yemen, with a note on E. quaitensis

Mats Thulin and Abdul Nasser Al-Gifri

Thulin, M. & Al-Gifri, A. N. 1995. Euphorbia applanata sp. nov. (Euphorbiaceae) from Yemen, with a note on E. quaitensis. - Nord. J. Bot. 15: 193-195. Copenhagen. ISSN 0107-055X.

The new species Euphorbia applanata, from limestone rocks in the Hadramaut Region in southern Yemen, is described and illustrated. The closely related E. quaitensis is recorded from a new locality in Hadramaut, and descriptions of its capsules and seeds are provided.

M . Thulin, Dept of Systematic Botany, Uppsala University, Villavagen 6, S-752 36 Uppsala, Sweden. - A . N . Al-Gift+, Dept of Biology, Faculty of Science and Education, Univ. of Aden, P.O. Box 6014, Khormaksar, Aden, Yemen.

Introduction Three endemic species of Euphorbia are previously known from the Hadramaut Region in southern Yemen: E. meuleniana 0. Schwartz, E . quaitensis S. Carter (only known from type locality) and E. rubriseminalis S. Car- ter.

During field work in the area in Oct 1992 many po- pulations of E. meuleniana and E. rubriserninalis were seen, while E. quaitensis was seen in the type locality as well as in one new locality. However, also a distinctive new species obviously allied to E. quaitensis was found. Description and illustrations of this are provided below along with a note with additional information on E. quai- tensis.

Euphorbia applanata Thulin & Gifri sp. nov. Type: Thulin, Eriksson, Gifri & Lingstrom 8103, Yemen, Ha- dramaut, Mola Matar area, c. 14'47". 48"45'E, 6 Oct 1992 (UPS holotype, Aden Univ., K isotypes).

Species nova ab E. quaitensi S. Carter habitu applanato,

Accepted 7-7-1994 0 NORDIC JOURNAL OF BOTANY

foliis angustioribus et seminibus caruncula fimbriata dif- fert. - Figs 1, 2A-C.

Perennial with soft-wooded stems, much-branched at ground level and forming flat mats to several dm in diam.; flowering branches to 10 mm long, sulcate, pu- bescent with short crisped hairs. Leaves linear or occa- sionally linear-lanceolate, up to 12 x 1.6 (-3) mm, acute at the apex, entire, & involute, somewhat fleshy, pu- bescent with short & crisped hairs on both sides or below only, tapering below into a narrowly winged petiole-like base; stipules reduced to minute filiform glandular bod- ies, deciduous. Umbels 2-3-branched; rays up to 2.5 mm long; bracts similar to the leaves. Cyathia solitary, termi- nal or pseudo-axillary, c. 2-2.5 mm in diam., with cup- shaped involucres, pubescent with short crisped hairs in upper part; glands 5, transversely oblong, c. 0.5 x 0.8-1 mm, quite separate, subentire to shallowly lobed, reddish green; lobes 5, rounded, c. 0.5 mm in diam., pilose. Male flowers: bracteoles filiform, c. 1.5 mm long, ciliate in upper part; pedicels c. 1.6 mm long; filaments c. 0.5 mm long; anthers c. 0.4 mm long. Female flower: ovary ex- serted, pubescent with short appressed hairs; styles c. 1.5 mm long, pubescent, united in basal half, with spreading bifid apices. Capsule exserted on a finally erect pedicel up to c. 5 mm long, broadly oblong, shallowly 3-lobed, c.

Nord. J. Bot. 15 (2) (1995) 193

Fig. 1. Euphorbia app from type locality.

llanata.

4 x 3 mm, pubescent with short appressed hairs, becom- ing reddish brown. Seeds oblong, compressed, 2.8-3.6 x 1.5-1.8 mm, acute at the apex, very finely pitted, other- wise smooth, silvery grey; caruncle cap-like, c. 1 mm wide, cream with a white fimbriate margin. - Figs 1, 2A-C .

Distribution and habitat. Euphorbia applanata is known only from the type locality, where it is locally common in crevices of flat limestone rocks (Fig. 1) at c. 1850 m altitude. Other plants growing on these rocks include, among others, Euphorbia hadramautica, E. inaequilat- era, Endostemon tereticaulis, Solanum carense, Coela- chyrum poiflorum, Dorstenia foetida and Haplophyllum amoenum, the last-mentioned species being another obvi- ously local endemic in the area.

Taxonomic remarks. Euphorbia applanata, with its oblong, well exserted capsule and dorsiventrally com- pressed seeds with a cap-like transverse caruncle clearly belongs to a group of species within subgen. Eremophy- ton (Boiss.) Wheeler including, among others, E. pirottae Terrac. and E. quaitensis. The nearest relative almost certainly is E. quaitensis, which is also a soft-wooded dwarf perennial with an indumentum of minute crisped hairs, and has very similar cyathia and male and female flowers (Carter 1988).

However, E . applanata differs markedly from E . quai- tensis in forming dense, flat mats on the ground, with the pedicels of the female flowers lifting the ripe capsules

above the vegetative parts of the plant. Further, the leaves are narrower (linear or occasionally linear-lanceolate and up to 3 mm wide versus lanceolate to obovate and up to 8 mm wide), and the caruncle of the seeds has a fimbriate margin (Fig. 2C) as opposed to the entire margin in E. quaitensis (Fig. 2D). According to S. Carter (pers. comm.) the fimbriate margin of the caruncle in E. appla- nata is a most unusual feature not noticed by her in any other species of the genus.

Euphorbia quaitensis S. Carter This species was seen in the type locality along the road between A1 Mukalla and Sayun in Hadramaut (c. 14"50'N, 49"OO'E) in Oct 1992, but was not collected in order to save the rather limited number of individuals seen. However, a richer locality was later found further to the north-east with hundreds of plants in a gentle lime- stone slope at c. 1220 m altitude. Here also plants with fruits and seeds (Fig. 2D) were found, thus making pos- sible the following additions to the description:

Capsule exserted on a pedicel up to c. 3 mm long, broadly oblong, c. 4 x 3 mm, pubescent with short ap- pressed hairs, becoming brownish. Seeds oblong, com- pressed, 3-3.5 x 1.6 mm, acute at the apex, slightly rugose and very finely pitted, greyish brown; caruncle

194 Nord. J. Bot. 15 (2) (1995)

C D

Fig. 2. A-C: Euphorbia upplanata, from Thulin et al. 8103. A: Flowering branch, x 5 . - B: Capsule, x 10. - C: Seed, x 10. - D: E . quaitensis, seed, x 10, from Thulin et al. 8375.

cap-like, c. 1.5 mm wide, cream with a white entire indebted to Ms Kerstin Thunberg for the drawing in Fig. 2, and to Ms Susan Carter for comments on the manuscript.

margin.

Yemen. Hadramaut: 68 km along the pipeline route from the crossing with the Ressib road, 15"06", 49"24'E, 13 Oct 1992, Thulin, Eriksson, Gifri & Lingstrom 8375 (K, UPS). Reference

Carter, S. 1988. Euphorbia quaitensis. - In: Boulos, L., A contribution to the flora of South Yemen (PDRY). Candollea 43: 564.

Acknowledgements - The field work in Yemen was supported by a grant from "Regnells botaniska resestipendium". We are

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