Centaurea serowensis Negaresh, 2023

Negaresh, Kazem, Yousefi, Zohreh & Kaya, Yusuf, 2023, A new species of Centaurea sect. Acrocentron (Asteraceae, Cardueae) from Iran, Phytotaxa 597 (1), pp. 37-50 : 38-43

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

Type: — IRAN. Prov. West Azerbaijan: Silvana toward Serow, Serow-Neychalan bifurcate, 1 km to Neychalan village , 37° 40’ 45” N, 44° 47’ 43” E, 2100–2200 m, 7 July 2014, Negaresh & Asadbegi 321 (holotype KHAU!, isotypes FUMH!, HUI!, KHAU!) .

Diagnosis: — Centaurea serowensis is related to C. lydia , from which it differs mainly in its plant dwarf, 1–4 cm height (vs. 10–35(–45) cm height), leaves indumentum loosely arachnoid (vs. subglabrous, scabrous, ± tomentose especially on upper side), basal and lower cauline leaves ca. 5–6 cm (vs. 10–15(–30) cm) long, involucres ovoid, 15–20(–25) × (12–) 15–20 mm (vs. globose, 25–35 × 22–35 mm), phyllaries indumentum loosely arachnoid (vs. glabrescent), appendages medium-sized, concealing partly of phyllaries only (vs. large, totally concealing the phyllaries), inner phyllaries 10–13 mm (vs. 20–28 mm) long, median appendages triangular, 8–15 × 2–4 mm (cilia excluded) (vs. orbicular, 20–35(–40) × 8–12 mm (cilia excluded)), central florets 25–27 mm (vs. 32–35 mm) long.

Descriptions: —Perennial plant with a woody base and long string-like roots (up to 15 cm), dwarf, usually opaque green all over, with remains of stems and leaf bases of the previous year. Stems ca. 1 to 2, simple or branched in basal part, ascending, 1–4 cm tall, ca. 2–2.5 mm in diameter at base, with thin yellowish striations, densely covered with arachnoid hairs. Leaves rigid, often divided, loosely covered with arachnoid hairs, up to 5 mm long, densely on midrib and veins, rarely mixed with sessile glands. Basal and lower cauline leaves small, ca. 5–6 cm long, lyrate, segments in 1–2 pairs; terminal segments much larger, lanceolate-oblong, 3–4 × 1.8–2 cm, coarsely tooted at margins; lateral segments narrowly lanceolate, obtuse at apex; rarely simple. Median and upper cauline leaves with short petiole or sessile, 5–7 cm long, pinnatisect or lyrate, segments in 5–7 pairs; terminal segments larger, triangular to lanceolate, 1.5– 1.8 × 0.8–2 cm, coarsely tooted at margins; lateral segments narrowly oblong or narrowly lanceolate (often additional small segments between the larger ones), entire or denticulate, acute at apex. Capitula heterogamous, solitary at end of branches, sessile or with short peduncle up to 1 cm. Involucres ovoid, concave at base, 15–20(–25) × (12–) 15–20 mm. Phyllaries multiseriate, coriaceous, imbricate, green, loosely covered with arachnoid hairs. Outer phyllaries ovate, 2–4 × 2.5–3 mm; median phyllaries broadly ovate to oblong, 6–10 × 4–6 mm; inner phyllaries oblong or linear, 10–13 × 4–6 mm, with a hyaline border. Appendages medium-sized, concealing partly of phyllaries only, ciliate, decurrent, straw-coloured or light brown, triangular, 2–4 mm wide at base (cilia excluded), the median ones 8–15 mm long, the inner ones suborbicular and spineless; cilia whitish, scabrous, numerous, 8–12 on each side, (1–) 2–4 mm long, suberect; spine robust, brownish, 5–8 mm long (in middle appendages), longer than adjacent cilia. Flowers pink or purple; central florets hermaphrodite, 25–27 mm long, with 5 equal and acute lobes, with deeply orange nerves, tube yellow; anther tube slightly shorter than corolla, apical appendages acute; stigma deeply purple, longer than corolla, up to 4 mm, symmetrically bifid, 0.6–0.8 mm long, pubescent; peripheral florets sterile, 4-lobed, limb lobe linear, 5–6 mm long, slightly radiant, slightly longer than the central ones. Receptacle umbilicate, setose, with 10–12 mm long smooth bristles. Achenes dimorphic; fertile achenes oblong or oblong-lanceolate, 4.2–4.8 mm long, 1.8–2 mm wide, laterally compressed, whitish, smooth, rounded at apex, densely sericeous; insertion areole lateral, ca. 0.8–1 mm long; pappus double, persistent, multiseriate, scabrous, whitish, 8–9 mm long, bristles of inner rows much shorter than outer ones, ca. 2.5 mm long. Sterile achenes cylindrical, yellowish, 4–5.2 mm long; pappus double, ca. 2 mm long, bristles of inner rows much shorter, sometimes absent.

Etymology: —The specific epithet refers to Serow town, where the new species was found.

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

Paratypes: — IRAN. Prov. West Azerbaijan: Silvana toward Serow , 37° 40’ 50” N, 44° 47’ 48” E, 2150 m, 1 July 2014, Negaresh et al. 3 22 ( KHAU!, HUI!); Negaresh et al. 323 ( KHAU!) .

Conservation status: — Centaurea serowensis is known only from the type locality. After detailed field investigations, no other population was found in the surrounding area. The only known population covers an area of ca. 1000 m 2 and consists of ca. 80 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. serowensis should be considered ‘Critically Endangered’ (CR) [criterion B2ab].

Distribution, habitat and ecology: — Centaurea serowensis is a rare endemic of West Azerbaijan Province, NW Iran ( Fig. 3 ). It is an Irano-Turanian element, and grows on rocky slopes, gravel slopes, in high-montane zone, at elevations of 2100–2200 m ( Fig. 1 ). In addition, some other plants that occurred in the area were Pistacia atlantica , Cirsium arvense , Gundelia tournefortii , Centaurea virgata subsp. squarrosa , Taraxacum montanum , Echinops polygamus , Artemisia austriaca , Myosotis alpestris , Alyssum dasycarpum , Astragalus lagopoides , Onobrychis cornuta , Marrubium astracanicum , Ziziphora tenuior , Papaver orientale , Bromus tectorum , Hordeum marinum , Stipa barbata , Amygdalus lyscioides , Crucianella gilanica , Verbascum speciosum .

Relationships: — Centaurea serowensis belongs to C. sect. Acrocentron , which includes taxa with stems usually branched in the upper part, lyrate or pinnatisect to bipinnate, not decurrent leaves, few medium-sized or large capitula, oblong-ovoid to subglobose involucres, purple or yellow flowers, and decurrent appendages ending in a spine ( Wagenitz 1975, 1980, Ranjbar & Negaresh 2013b). It is similar to C. lydia Boissier (1843: 20) , which is endemic to W Turkey, in dissection of leaves, color of flowers, width of achenes and length of bristles of the inner rows of pappus ( Fig. 4 ), but differs in some important characters (see Table 1 ). Furthermore, C. serowensis occurs at elevations higher than 2100 m, whereas C. lydia occurs at elevations lower than 1000 m.

Centaurea serowensis shares some characters such as the length of stem, the dissection of leaves, the length of spine and the color of flowers with C. bojnordensis Ranjbar, Negaresh & Joharchi (2014: 116) , but differs from that species as stated in Table 1 . Moreover, they are geographically isolated; the former is confined to mountains of Serow (West Azerbaijan Province) in NW Iran, the latter is a narrow endemic to North Khorasan Province in NE Iran ( Fig. 3 ).

This species is also similar to C. urvillei subsp. deinacantha , from Iran and Iraq, especially because of the life form, dissection of leaves, color of appendages and flowers ( Fig. 5 ). However, it differs from C. urvillei subsp. deinacantha in some characters like life form, ramification of stems, length of leaves, size and shape of involucres, indumentum of phyllaries, size of appendages, length of florets, achenes and pappus ( Table 1 ).

Figures

FIGURE 1. Centaurea serowensis Negaresh (Negaresh & Asadbegi 321, KHAU). Scale: 1 cm.

FIGURE 2. Centaurea serowensis Negaresh (Negaresh & Asadbegi 321, KHAU). A. close-up of capitulum.B. sterile achene.C–E. fertile achenes with pappus. F. indumentum of leaf. Scale A–E = 6 mm.

FIGURE 3. Distribution of Centaurea serowensis (square), C. lydia (stars), C. bojnordensis (triangles) and C. urvillei subsp. deinacantha (circles).

FIGURE 4. Centaurea lydia Boissier (Boissier s.n., G-BOIS).

FIGURE 5. Centaurea urvillei subsp. deinacantha (Boiss. & Hausskn.) Wagenitz (Haussknecht 584, G-BOIS).