Dionysia avia Mehregan, Younesi & Lidén, 2021

Mehregan, Iraj, Younesi, Simin & Lidén, Magnus, 2021, Donysia avia (Primulaceae), a new species from Zagros Mountains, Iran, Phytotaxa 511 (3), pp. 296-300 : 297-299

Dionysia avia Mehregan, Younesi & Lidén sp. nov. ( Figs. 1 , 2)

Type: IRAN. Esfahan: Semirom, Padena, Dena mountain chains, below Qalat-Bozi peak, 51.374° E, 31.016° N, 3800 m, 5 Jun. 2015, Hosseinimehr 14816 (holotype, IAUH; isotype, TARI) .

styled flower; C – E . Leaves; F. Bract; G. Calyx; H. Indumentum of eglandular hairs. Scale bars—for A – E = 10 mm; for F – G = 2 mm; for H = 1 mm. Drawn by M. Lidén from part of the type material (Hosseinimehr 14816, IAUH) .

Description: Cushions moderately dense to rather lax. Branches with imbricate leaves in overlapping whorls in the upper part, bare below, pale grayish brown with a slight reddish lustre, slightly covered by eglandular hairs. Leaves green, entire, oblong, apex obtuse, (3–)5–10 × 1–2.5 mm, margin ciliate, with eglandular hairs to 0.5 mm long on both sides or only adaxially, with sessile or shortly stalked glands on both surfaces, but most frequently abaxially. Bracts 1 or rarely 2, narrow, similar to calyx lobes, 3–4 mm long. Flowers single, sessile or very shortly stalked; pedicel <1 mm long, with eglandular hairs. Calyx divided to the base, much smaller than leaves, 2.5–3 mm long; lobes oblanceolate, subobtuse at apex, gland-dotted abaxially, with eglandular hairs 0.2–0.3 mm long on both sides and marginally. Corolla yellow, densely covered by eglandular hairs outside, hairs conspicuously longer in distal part; tube of short-styled flowers up to 15 mm long, that of long-styled flowers ca 10 mm long; limb to 10 mm across, lobes obovate, ca. 5 mm long, apex emarginate. Style of short-styled flowers 5–6 mm long, that of long-styled flowers not exserted, up to 9 mm long. Stamens in short-styled flowers inserted 1/3 from the base, in long-styled flowers inserted 4/5 from the base. Ovary small, rounded, with 5–6 ovules; seeds (immature) rounded, small, ca 0.4 mm long.

Etymology: The specific epithet means “isolated, off the trodden road”. Other species of Dionysia described from Dena mountain ranges usually grow at altitudes up to 3400 m. Our new species seems to be highly isolated and somehow unique in being adapted to much higher altitudes.

Similar species: This species is similar to Dionysia bachtiarica Bornm. & Alexeenko in Bornmüller (1904: 515) in growth habit, leaf shape, indumentum and calyx size. However, D. avia differs in isophylly (versus very pronounced anisophylly in D. bachtiarica with overwintering leaves small, with pale thickened margin; spring leaves 3–5 times longer), marginal hairs of leaves and calyx lobes finer and shorter, 0.2–0.3 mm long (versus coarser and longer hairs, up to 1 mm long), leaves hairy (versus glabrous abaxially), calyx lobes 2.5–3 mm long, hairy (versus 4 mm long, glabrous on both sides), corolla hairy (versus glabrous) and capsules with 5–6 seeds (versus more than 15 seeds). Dionysia avia may find its closest relative in D. lamingtonii Stapf in Decades Kewenses (1913: 43). A character unique to these two species is the entire leaves with a conspicuous indumentum of long multicellular eglandular hairs on the adaxial sides and margins of the leaves, which is absent or present on the abaxial side, even on successive leaves of the same individual. The two species have, however, very different habits, and are easily distinguished by a number of characters. Dionysia avia is relatively loose (versus very compact) and soft plant (versus hard), green (versus conspicuously blue-green), much larger in all parts with glands (versus without glands and glandular hairs, except on the corolla). Further, the calyx is split to the base (versus split from 60–80%). Very rarely encountered strongly aberrant shade forms of D. lamingtonii have loose growth and almost as long leaves as D. avia , but the other characters still clearly separate the two species.

Ecology and distribution: Dionysia avia is only known from the type locality in the alpine area of Dena mountains on limestone. It is not confined to vertical sites, but grow also on sloping rocks ( Fig. 3 ).

Conservation status: Like D. drabifolia Bunge (1871: 558; syn.: D. termeana Wendelbo (1970: 306)) , another Kuh Dena endemic, D. avia is only known from the type locality. The restricted known occurrence and low number of individuals (ca 100 mature plants) suggests the category “Critically Endangered” (CR B1a or B2a) according to the IUCN manual (2012).

Figures

FIGURE 1. Dionysia avia. A. Flowering branch with corolla tube cut slightly above the calyx lobes; B. Corolla of short

FIGURE 3. Distribution map of Dionysia avia, D. bachtiarica and D. lamingtonii.