Euphorbia boreo-baluchestanica Pahlevani, 2017

Pahlevani, Amir H., 2017, Four new species of Euphorbia sect. Pithyusa (subg. Esula, Euphorbiaceae) from SW Asia, Phytotaxa 312 (1), pp. 83-93 : 84-88

Euphorbia boreo-baluchestanica Pahlevani , sp. nov. ( Fig. 3 )

Euphorbia boreo-baluchestanica is closely related to E. prolifera . It differs from the latter by orbicular to obovate cauline leaves (instead of linear, lanceolate or oblanceolate ones), 7–18 × 5–11 mm (instead of 20–50 × 2–5 mm); cyathial glands with two long and mostly lobate horns (instead of very short and simple or rather denticulate ones), narrowly conical (instead of chubby conical), smaller (3.5–4 × 3–3.5 mm instead of 4.5 × 6 mm) capsules; narrowly conical, irregularly pitted (instead of ovoid-subglobose, shallowly rugulose-ridged), smaller seeds (2.2–2.5 × 1.7–2 mm instead of 3.5 × 3 mm), larger and permanent caruncles (instead of minute and caducous ones).

Type:— PAKISTAN. Baluchistan: Kalat , between Basima and Surab, 1600–1700 m, 28º29’N, 66º19’E, 21 April 1965, Rechinger 28318 (holotype W!; isotypes B100846955 !, M0224484 !) .

Perennial herbs, erect, 25–35 cm high, several shoots arising from rather woody stock, glabrous, glaucous. Stem base 2.5–3 mm diameter. Cauline leaves sessile, orbicular to obovate, 7–18 × 5–11 mm, rounded to cuneate at the base, margin entire to subentire, cartilaginous, apex mucronulate or rounded, glabrous, glaucous, with 3–5 palmate nerves. Terminal rays (3–)4(–5), two to three times dichotomous, usually elongated (up to 12 cm), axillary rays 3–8, more elongated than the terminal ones (up to 20 cm), once or mostly twice dichotomously. Ray-leaves similar to cauline leaves, 3–4; raylet-leaves similar to the cauline and ray leaves but remarkably smaller (6–10 × 6–12 mm). Cyathial involucre campanulate, 2.5–2.8 mm in diameter, lobes lanceolate, lacerate; glands 4, gland appendages lunate, brown, with 2 long, yellowish horns, mostly 2-lobate. Ovary smooth, glabrous, styles united at the base, bifid, 2 mm long, the stigmas thickened. Capsules conical, superficially trilobate, 3.5–4 × 3–3.5 mm, glabrous, occasionally whitish punctate, pedicels, 3.5–4 mm long. Seeds conical, irregularly pitted, 2.2–2.5 × 1.7–2 mm, yellowish to light brown, caruncle conical, 0.7–1 × 0.5 mm, brownish.

Additional specimens examined (paratypes): — PAKISTAN. Baluchistan: Kalat , 24 km S Surab, 28º29’N, 66º19’E, 1 April 1965, Rechinger 27380 ( M!, W!, WU!) ; Kalat, Surab, 69 km from Kalat towards Khuzdar , 1700 m, 28º29’N, 69º19’E, 1 April 1965, Rechinger 27371 ( M!) ; Kalat , 9 May 1963, Siddigi 2009 ( K!) ; Skalku [Iskalku], Kalat , 2134 m, 19 June 1957, Akbar 1882 ( K!) ; Kalat, Gandava pass, Stocks 401 ( K!) ; 30 km S of Quetta in Pass , 2000 m, 19 July 1969, Andersen & Petersen 464 ( K!) .

Etymology: —The epithet ‘ boreo-baluchestanica ’ refers to northern Baluchistan, Pakistan, where the species occurs.

Ecology and conservation status: — Euphorbia boreo-baluchestanica has been collected by several botanists from the semi-desert zone of lower mountane regions at elevation between 1600–2130 m on gravelly and stony beds. According to the IUCN redlist categories and the conservation analysis, it is suggested to evaluate its conservation status as ‘vulnerable’ (VU) (IUCN 2017).

Affinity and plant geography: —The newly discovered species belongs to section Pithyusa and is sister to E. prolifera Buch. -Ham. (in Don 1825: 62) (Pahlevani, unpubl. data). Euphorbia boreo-baluchestanica is limited to the N part of Baluchistan, Pakistan near the frontier of Afghanistan ( Fig. 2 ). In addition to obvious morphological differences which have been mentioned in diagnosis, its chorotype is also different from E. prolifera . Euphorbia boreo-baluchestanica is an Irano-Turanian element, whereas, E. prolifera is a Sino-Himalayan element ( Geltman 2015), occurring from SW China, Thailand, Burma, Nepal and N India to NW Pakistan as the most western part of its distribution. Our unpublished molecular data indicate that these two species and E. erythradenia Boissier (1846: 92) , E. gedrosiaca Rechinger, Aellen & Esfandiari (1951: 220) , E. plebeia Boissier (1846: 93) , E. spartiformis Mobayen (1984: 160) and E. sulphurea Pahlevani (2015: 353) form a distinct and supported clade in sect. Pithyusa. Of the seven species of this group, two occur in Pakistan and the five remaining ones are endemic to Iran ( Pahlevani et al. 2015). With the exception of E. prolifera , other members of this clade are Irano-Turanian elements, distributed from south-eastern parts of the Zagros Mountains toward Baluchistan of Iran and Pakistan. The specimens deposited in the mentioned herbaria have been mistakenly identified and reported as E. microsciadia Boissier (1846: 89) by Radcliffe-Smith (1986).

Taxonomic note: In addition to the diagnostic characters mentioned above, there are some more morphological differences between E. boreo-baluchestanica and E. prolifera , including cauline leaves cuneate to rounded at the base (not attenuate or truncate), mostly with 3–5 conspicuous palmate nerves (instead of inconspicuous ones or only midrib visible), mostly mucronulate or rounded apex (instead of obtuse, acute to subacute apex), absence of densely-leafy sterile shoots (instead of presence of densely-leafy sterile shoots).

Figures

FIGURE 2. Geographical distribution of Euphorbia acanthoclada and E. boreo-baluchestanica.

FIGURE 3. Photograph of holotype specimen of Euphorbia boreo-baluchestanica.