Euphorbia ziaratensis 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 : 90-92

Euphorbia ziaratensis Pahlevani , sp. nov. ( Fig. 6 )

Euphorbia ziaratensis is closely related to E. sulphurea , but differs by being glabrous and with purplish colour of the plants, smaller (3–5 × 1–2 mm instead of 5–13 × 3–7 mm) ovate-lanceolate cauline leaves with mostly irregularly minutely denticulate margins, cyathial glands with two long stramineous horns, larger (4–4.5 × 3–3.2 mm instead of 3.1–3.5 × 2.7–3 mm) capsules, and rather longer seeds with obscure pits, compressed and flattened.

Type:— PAKISTAN. Baluchistan: Ziarat, ± 2440 m, 28 May 1968, Zaffar Ali 4827 (holotype K!).

Glabrous, procumbent-ascending perennial herbs, 4–8 cm high. Many stems arising from caudiculi borne upon the rootstock. Cauline leaves sessile, ovate-lanceolate, 3–5 × 1–2 mm, tapering at the base, margin subentire to irregularly minutely denticulate, apex subacute, obtuse to rounded, glabrous. Terminal rays 3–4, one to two times dichotomous, with no axillary ray. Ray-leaves 3–4, rhombic-ovate, 4–5 × 3–5 mm, subacute or obtuse, cuneate at the base; raylet-leaves similar to ray-leaves but smaller, truncate at the base. Cyathial involucre campanulate, 1.5–2 mm in diameter, lobes lanceolate, lacerate; glands 4, gland appendages transversely ovate, reddish, with two long, stramineous and subulate horns. Ovary smooth, glabrous, styles united at the base, shortly bifid, 1 mm long, the stigma slightly thickened. Capsules conical, 4–4.5 × 3–3.2 mm, shallowly trilobate, glabrous. Seeds compressed-conical, 2.5–2.8 × 1.5–1.8 mm, shallowly pitted, dark brown, caruncle conical, 0.7–1 × 0.8–1 mm.

Additional specimens examined (paratype): — PAKISTAN. Baluchistan: Quetta, in jugo E Ziarat, 2500–2600 m, 30º20’N, 67º30’E, 13 May 1965, Rechinger 29395 ( W!).

Etymology: —The epithet ‘ ziaratensis ’ refers to the type locality of the new species in Ziarat, a place in northern Baluchistan of Pakistan.

Ecology and conservation: —Based on information from herbarium specimens, E. ziaratensis is found in the alpine zone of the highlands of northern Baluchistan on stony ground at 2400–2600 m elevation. So far, only two specimens of the species have been found in the studied herbaria, both of which are from the type locality in Ziarat or nearby ( Fig. 5 ). It seems E. ziaratensis is very rare. Because of its rarity and vulnerability, I suggest the evaluation of this delicate species as ‘critically endangered’ (CR) according to the International Union for Conservation of Nature (IUCN) threatened categories (IUCN 2017).

Affinity and plant geography: —Based on the morphological characteristics of E. ziaratensis , it belongs to sect. Pithyusa. The type specimen has been mistakenly considered as E. aucheri Boissier (1846: 94) from Pakistan by Radcliffe-Smith (1986). But after close examination of the specimens, it was found that it not only does not belong to sect. Herpetorrhizae ( Prokhanov 1933: 56) Prokhanov (1949: 456), but it is a member of section Pithyusa . The most distinguishable features to separate the new species from E. aucheri are its capsules and seeds ( Pahlevani et al. 2015). It is remarkable that the sole specimen of E. aucheri reported from Pakistan ( Radcliffe-Smith 1986) in fact belongs to this new species. Euphorbia ziaratensis was found from highlands of northern Baluchistan of Pakistan ( Fig. 5 ), which is a hotspot of medicinal and endemic plants in Pakistan (Ali & Qaisar 1986, Bibi et al. 2015).

Figures

FIGURE 5. Geographical distribution of Euphorbia kavirensis and E. ziaratensis.

FIGURE 6. Photograph of holotype specimen of Euphorbia ziaratensis.