Onosma bakhtiarica Khajoei Nasab & Zeraatkar

Nasab, Farzaneh Khajoei & Zeraatkar, Amin, 2024, A new species of Onosma (Boraginaceae) from Bakhtiari Mountains in Iran, Phytotaxa 655 (3), pp. 272-282 : 273-278

Onosma bakhtiarica Khajoei Nasab & Zeraatkar sp. nov. ( Figs. 1–6 ).

Type :— Iran. Chaharmahal and Bakhtiari province , north of Ardal, Tang-e Beheshtabad, 32.0429° N 50.6484° E, 1720 m a.s.l, 30 May 2023, A. Zeraatkar no. 7141 (Holotype D!; Isotypes: D!) .

Diagnosis:— Onosma bakhtiarica is most similar to O. pachypoda Boiss. and O. sericea Willd based on the plant height, rosette leaf size, soft and silky setae with glabrous tubercles, corolla length, lanceolate calyx lobes united in 1/4 of the base, flowering calyx length, bract size, filament, and anther lengths. Onosma bakhtiarica has other similarities with O. sericea such as its light brown nutlet, rosette leaf with a long petiole, and cauline leaf with an acute apex. On the other hand, it is similar to O. pachypoda due to the dense short hairs that cover the exterior of the corolla. However, it is distinguished from O. pachypoda by the rosette leaf shape, shape of rosette leaf apex, having a long petiole, shorter cauline leaf, cauline leaf width, cauline leaf shape, cauline leaf apex shape, arrangement of setae, corolla color and shape, shorter pedicel length in flowering and fruiting, bract shape, nutlet features, and a hairy annulus. It is also easily distinguished from O. sericea by its rosette leaf shape, the shape of rosette leaf apex, cauline leaf size and shape, arrangement of setae, corolla color and shape, the dense short hairs covering the exterior of the corolla, shorter pedicel length in flowering and fruiting, shorter fruiting calyx, bract shape, nutlet features, and a hairy annulus.

Description:—Perennial, pale green, suffruticose, 25–40 cm tall. Stems erect or nearly arcuate ascending, simple at the base, and sub-branched at the superior parts. Rosette leaves elliptic, obovate, oblong-elliptic, mucronate, lamina 15–40 × 5–20 mm, with revolute margin, attenuate toward base on a long petiole; petiole 10–40 mm long. Setae with small glabrous tubercles (sect. Onosma , subsect. Haplotricha), white or yellow, 0.3–1.4 mm, sparsely adpressed; tubercles diameter 0.1–0.5 mm. Cauline leaves elliptic-lanceolate, 30–45 × 10–17 mm, acute, sessile to petiolate. Inflorescence with scorpioid cymes, elongated after flowering, each cyme with 5–18 flowers. Bracts elliptic-lanceolate, narrowly acute, sessile, 4–10 × 2–4 mm. Pedicels thin, up to 1 mm, after flowering stout, up to 2 mm. Calyx lobes united in 1/4 of the base, lanceolate, narrowly acute at apex, grayish, accrescent, flowering calyx 13–17 mm long, fruiting calyx 17–24 mm long, outside densely pubescent, spreading setose, especially at the 1/3 leading to the base, inside pubescent. Corolla clavate, yellow-reddish, becoming blue when dried, 20–22 mm, lobes triangular, revolute, 3–4 × 2–3 mm, finely pubescent outside. Anthers connected at the base, shorter than corolla, 5–8 mm; free part of filaments length 7–9 mm. Style 19–25 mm, filiform, exserted, capitate; stigma distinctly bilobed. Annulus with long hair (up to 5 mm long). Nutlet 5–6 × ca. 5 mm, light brown, broadly ovoid, warty, covered with rounded protuberances.

Phenology:—Flowering occurs from May to June, and fruiting from June to July.

Distribution, ecology and conservational status:— Onosma bakhtiarica is a xerophytic and scree element found in the Irano-Turanian floristic region ( Fig. 8 ). All collections and observations come from one narrow valley at altitudes between 1720 and 1800 meters above sea level. Onosma bakhtiarica thrives on steep slopes with a high percentage of screes and stones, and the ground has sparse vegetation ( Fig. 2 ). The valley at the slopes is covered by Prunus haussknechtii C.K.Schneid. associations mixed mostly by woodlands such as Ficus carica subsp. rupestris (Hausskn.) Browicz , Rhamnus persica Boiss. Celtis glabrata Steven ex Planch. , Rosa elymaitica Boiss. & Hausskn. , Prunus scoparia (Spach) C.K.Schneid. , Crataegus azarolus var. aronia L., Ampelopsis vitifolia (Boiss.) Planch. , Prunus microcarpa C.A.Mey. , Prunus mahaleb L. The newly discovered species is currently only known from its type location, and the population consists of fewer than 30 individuals. The Onosma bakhtiarica population has been affected by human activities, particularly due to road construction. The total area occupied by the species is less than 0.001 km 2. Based on the IUCN Red List guidelines (2022), the conservation status of the new species is categorized as critically endangered ( CR).

Figures

FIGURE 1. Holotype of Onosma bakhtiarica Khajoei Nasab & Zeraatkar. Photograph by A.Z.

FIGURE 2. Habit and habitat of Onosma bakhtiarica Khajoei Nasab & Zeraatkar. Photograph by A.Z.

FIGURE 3. Photos of Onosma bakhtiarica: A) inflorescence during flowering, B & C) inflorescence during late flowering and the start of fruiting, D) basal and cauline leaves. Photograph by A.Z.

FIGURE 4. LM micrographs of the haplotrichous leaf surface indumentum of Onosma bakhtiarica. Basal leaves: (A) upper surface; (B) lower surface. Cauline leaves: (C) upper surface; (D) lower surface. Scale bars: 1 mm. Photograph by F.Kh.

FIGURE 5. Onosma bakhtiarica, A) inner surface of the corolla, B & C) outer surface of the corolla, D & E) annulus with long hairs, F & G) flowers, H) details of outer surface of the corolla. Scale bars:A–C & G: 1 cm. D–F: 0.5 cm. H: 5 mm. Photograph by A.Z.

FIGURE 6. Nutlets of Onosma bakhtiarica A) ventral surface B) dorsal surface C) lateral view D) epidermis ornamentation. Scale bars: 1 mm. Photograph by A.Z.

FIGURE 8. Distribution map of Onosma bakhtiarica, O. pachypoda, and O. sericea in Iran. Map by F.Kh.