Centaurea zirjubiensis Negaresh, sp. nov. (Figs. 1, 2)

Type: — IRAN. Prov. Kermanshah: Badr rural district, Zirjubi village, 34°44'51.5" N, 46°37'19.1" E, 1350–1380 m, 27 May 2025, Negaresh & Kamalnejad 883 (holotype KHAU!, isotypes FUMH!, HSB!, KHAU!).

Diagnosis: — Centaurea zirjubiensis is related to C. alfonsoi, from which it differs mainly in its stem always simple (vs. often branched from near base to median part), appendages rigid, distinctly ciliate, spine much longer than adjacent cilia (vs. chartaceous, sometimes acute at apex or appendiculate, cilia short, sometimes cilia very few or lacking, spine longer than adjacent cilia, rarely very short and mucronate), median appendages brown to dark brown, 15–18 × 6–8 mm (including cilia and spine), cilia 5–8 on each side, gradually narrowing into a 8–10 mm spine (vs. straw-coloured, 11–13 × ca. 10–11 mm (including cilia and spine), cilia 3–5(–6) on each side, gradually narrowing into a 5–7 mm spine), inner appendages dark brown, 2–4 mm wide (including cilia) (vs. pale brown-reddish, 4–10 mm wide (including cilia)), central florets 38–42 mm (vs. 46–48 mm) long, achenes oblong, 7–7.5 × ca. 3 mm, brown, insertion areole ca. 0.5 mm long (vs. lanceolate, 9–10 × 3.2–3.8 mm, shiny, yellowish, insertion areole ca. 1 mm long).

Descriptions: —Biennial plants, with thick taproot, whole plant usually pale green, 70–85 cm tall; collum neck with fibrous remnants of petioles from previous year. Stem erect, always simple, ca. 10 mm in diam. at base, cylindrical, with thick yellowish striations, loosely leafy from lower to median part, lower to median parts densely covered with long hirsute-articulate hairs, up to 3 mm long, mixed with sessile gland hairs, upper part glabrous or sparsely covered with arachnoid hairs. Leaves rigid, papyraceous (on drying), always undivided, below prominently with elevated veins, loosely covered with hirsute-articulate hairs up to 2 mm long and glandular hairs, more densely on midrib and veins, sometimes upper ones mixed with arachnoid hairs. Basal leaves petiolate, simple, broadly triangular or broadly subcordate, 23–25 × 13–15 cm, with a 10–12 cm long petiole, cartilaginously denticulate, acute at apex. Lower cauline leaves simple, broadly triangular or broadly cordate, 20–28 × 10–15 cm, often with basal auricles, acute at apex, margin scabrous. Median cauline leaves sessile, simple, oblanceolate, 15–20 × 8–10 cm, broadly decurrent, up to 60 mm along stem, acuminate at apex, margin scabrous. Upper cauline leaves smaller, sessile, 6–10 × 3–4 cm, lanceolate or oblong, decurrent, up to 30 mm along stem, shortly mucronate at apex, margin subscabrous. Capitula several, 7 to 10, arranged in racemes, the upper capitula on peduncles 6–12 cm long, sometimes with bracts similar to phyllaries with small stramineous or chaffy appendages. Involucres subglobose, convex at base, 30–40 × 30–35 mm. Phyllaries multiseriate, green, yellow-greenish when dry, imbricate, coriaceous, densely tomentose; appendages medium-sized, concealing part of phyllaries only, erect, rigid, not decurrent; cilia erect, several, 5–8 on each side, 2–3 mm long; spines narrowly triangular, much longer than adjacent cilia. Outer phyllaries broadly oblong, 5–8 × 5–6 mm; appendages triangular, straw-coloured, 10–12 × 6–8 mm (including cilia and spine). Median phyllaries broadly ovate or broadly lanceolate, 10–15 × 8–10 mm; appendages elongate triangular, brown to dark brown, 15–18 × 6–8 mm (including cilia and spine), gradually narrowing into a 8–10 mm spine. Inner phyllaries lanceolate or lanceolate-linear, 22–30 × 5–10 mm, with hyaline margins; appendages narrowly lanceolate, dark brown, 10–15 × 2–4 mm (including cilia and spine), gradually narrowing into a 7–10 mm spine, sometimes lacerate. Flowers white in vivo, sulphureous in sicco; central florets hermaphrodite, 38–42 mm long, corolla 15–17 mm long, 5-lobed, lobes 7–8 mm long, with orange nerves, anthers ± equal to corolla, with apical appendages acute, anther tube pink, stigma exserted from corolla up to 3 mm; peripheral florets sterile, finely dissected, slightly shorter than central ones, 38–40 mm long, numerous (15–20 in each capitulum), conspicuous, not radiant, 4-lobed, limb lobes filiform, lobes 6–7 mm long. Achenes oblong, 7–7.5 mm long, ca. 3 mm wide, brown, rounded at the apex, glabrescent; insertion areole lateral, ca. 0.5 mm long. Pappus persistent, multiseriate, scabrous, whitish, 12–13 mm long, bristles of inner rows longer than others.

Etymology: —The specific epithet refers to Zirjubi village, where the new species is found.

Phenology: —Flowering in May and June, fruit ripening in June and July.

Paratypes: — IRAN. Prov. Kermanshah: Ravansar, near Sarabe Jaberi, 34° 41′ 47.05″ N, 46° 40′ 31.40″ E, 1350 m, 3 June 2024, Negaresh & Jafari 747 (KHAU!); Sardom village toward Ghelavin village, 2 km after Sardom village, 34° 43′ 11.15″ N, 46° 41′ 59.78″ E, 1375 m, 4 June 2024, Negaresh & Jafari 734 (KHAU!).

Conservation status: —Both documented collections of new species originate from locations adjacent to a road, covers an area of ca. 2000 m 2 and consists of ca. 200 individuals. Possible threats include deterioration of habitats (erosion), the location near a human settlement and restricted distribution. According to the IUCN red list categories and criteria (IUCN 2012), C. zirjubiensis should be considered ‘Critically Endangered’ (CR) [criterion B2ab].

Distribution, habitat and ecology: — Centaurea zirjubiensis is a rare endemic growing in Kermanshah Province, W Iran. It represents the Irano-Turanian floristic element, and grows on fallow fields and roadsides, at elevations of 1350–1400 m (Fig. 3B). The flowers of C. zirjubiensis are pollinated by some Lepidoptera and Scarabaeidae (Fig. 3A). In addition, other plants that occurred with the new species were Avena barbata subsp. barbata, Astragalus caraganae, Bromus tectorum, Centaurea amadanensis subsp. gymnoclada, Centaurea behen, Centaurea solstitialis subsp. solstitialis, Cephalaria syriaca, Crupina crupinastrum, Gundelia tournefortii, Hordeum marinum, Marrubium vulgare, Onobrychis melanotricha, Phlomis olivieri, Pisum sativum, Scabiosa rotata, Xeranthemum longipapposum.

Relationships: — Centaurea zirjubiensis belongs to C. sect. Cynaroides, which includes taxa often having racemose, spike or dichasial synflorescences, decurrent upper cauline leaves, ovoid to subglobose involucres, triangular to ovate or orbicular appendages that are not decurrent, and are usually ciliate and ending in a firm spine or spinule, and with pink, yellow or white flowers (Negaresh & Rahiminejad 2018). According to Negaresh & Rahiminejad (2018), C. sect. Cynaroides includes 37 species, of which 6 species, C. karamianiae Negaresh (2014: 230), C. nemecii Nábělek (1925: 44), C. mozaffarianii Negaresh (2018: 73), C. amadanensis Schultz Bipontinus (1847: 326), C. kamyaranensis Ranjbar & Negaresh (2014b: 322) and C. alfonsoi have white flowers. Centaurea zirjubiensis resembles C. alfonsoi, which is endemic to W Iran, in the color of flowers, number and status of peripheral florets. However, as shown in Table 1, C. zirjubiensis differs from the latter in some important characters such as simple stem, smaller leaves, rigid and distinctly ciliate appendages, median appendages brown to dark brown, 15–18 × 6–8 mm (including cilia and spine), cilia 5–8 on each side, gradually narrowing into a 8–10 mm spine, shorter flowers, oblong, brown and smaller achenes (Figs. 4B, 5F). In addition, the new species is like to C. karamianiae (endemic to W Iran), C. nemecii (native to SE Turkey and W Iran), C. mozaffarianii (endemic to W Iran) and C. amadanensis (native to SW to W Iran and NE Iraq) especially because of the color of flowers. However, it is easily distinguished from them by having peripheral florets numerous (15–20 in each capitulum), conspicuous (vs. very few (1–3(–5) in each capitulum), very inconspicuous), and appendages brown or dark brown (vs. straw-coloured) (Figs. 5A–5E). Centaurea zirjubiensis is also related to C. kamyaranensis, which is endemic to W Iran, especially because of the color of flowers and anther tube. However, it differs well from C. kamyaranensis by having habit 70–85 cm (vs. 130–140 cm) tall, lower part stem indumentum densely long hirsute-articulate (vs. glabrous), upper capitula on peduncles 6–12 cm long (vs. upper capitula on peduncles ca. 23 cm long), involucres subglobose, 30–40 × 30–35 mm (vs. globose or globose to conical, 40–50 × 40–50 mm), appendages erect, brown or dark brown (vs. subreflexed, pale purple to deeply purple), inner appendages 10–15 × 2–4 mm (including cilia and spine) (vs. 16–20 × 4–10 mm (including cilia and spine)), cilia 2–3 mm (vs. 2–5(–6) mm) long.