Centaurea phalacrica Brullo, Cambria, Crisafulli, Tavilla & Sciandr., 2021

Brullo, Salvatore, Cambria, Salvatore, Crisafulli, Alessandro, Tavilla, Gianmarco & Sciandrello, Saverio, 2021, Taxonomic remarks on the Centaurea aeolica (Asteraceae) species complex, Phytotaxa 483 (1), pp. 9-24 : 19-20

3. Centaurea phalacrica Brullo, Cambria, Crisafulli, Tavilla & Sciandr. , sp. nov. ( Figs. 1 , 4C , 6 )

Type: — ITALY. Sicily: Capo Rasocolmo (Messina), tra San Saba e Aquarone , rupi costiere metamorfiche, 38°17’50’’N 15°31’19’’E, 6 July 2020, G. Tavilla & S. Cambria s.n. (holotype CAT!; isotypes CAT, FI, PAL, MS) .

Diagnosis: — A Centaurea aeolica foliis basalibus 1-pinnatisectis usque ad 18 cm longis, confertim laciniatis, laciniis plerumque linearibus brevioribus, foliis caulinibus subellipticis circumscriptione, capitulis 3–7 basalibus foliolis praeditis saepe laciniatis, involucri phyllis magis numerosis, 5-nervatis, appendice coriacea, majore, longe fimbriata, floribus longioribus, lobis longioribus praeditis, stylo longiore, lobis stigmatis longioribus, acheniis majoribus, setis pappi irregulariter dispositis, intimis usque ad 3 mm longis differt.

Description: —Perennial herb with a woody rootstock. Stems erect, striate, with whitish-grey tomentum, 40–80 cm tall and 3–5 mm in diameter, simple, leafy. Leaves tomentose, whitish-grey; basal leaves usually on short sterile branches, more or less petiolate, 1–pinnatisect (exceptionally 2-pinnatisect), 7–18 × 2–4 cm, dense laciniate, with laciniae linear, 1–4 cm long, 1–4 (7) mm wide, acute at the apex, shortly mucronate; cauline leaves short petiolate to subsessile, subelliptical in outline, 1-pinnatisect, 1–16 cm long, with laciniae densely and irregularly inserted, linear, 1–4 cm long, 1–5 mm wide, apex acute, rarely obtuse, shortly mucronate. Capitula arranged in terminal racemes, ovoid, 10–15 mm long, 9–13 mm in diameter; phyllaries imbricate, up to 80, powdered, dorsally convex, usually 5-nerved, with terminal appendages straw-coloured, triangular, coriaceous, 2–3 mm long, 1.8–3 mm wide, fimbriate, with 7–15 fimbriae, 0.2–1.5 mm long; outer phyllaries ovate 4.5–6.5 × 1.8–2.8 mm, median phyllaries ovate-lanceolate, 6.5–10 × 3–4 mm; inner phyllaries linear-lanceolate, 10–13 × 1.6–3 mm. Florets purplish-pink; ray florets sterile, 20–21 mm long, with lobes unequal, 8–10 mm long; disc florets fertile, 19–20 mm long, with lobes equal, 5–5.5 mm long. Stamens 20–21 mm long, with filaments 13–13.5 mm long, fused below, free and hairy above; anthers 6.5 mm long. Style 20 mm long, ciliate at apex; stigmatic branches 3 mm long. Achenes oblong, 3.8–4 × 1.5–2 mm, sparsely villous, brownish, coronula very narrow, straw-coloured, with several irregular straw-coloured longitudinal ridges; pappus bristles irregularly arranged, brownish below and whitish above, the outermost ones 0.2 mm long, the innermost ones up to 2.5 (3) mm long.

Etymology: —The specific epithet refers to “ Phalacrium Promontorium ” ( Goltz 1576), nowadays Capo Rasocolmo near Messina (Sicily), where the new species is native.

Phenology: —The species flowers from June to July and fruits from July to August.

Distribution and ecology: — Centaurea phalacrica was discovered in a small locality known as Capo Rasocolmo, a little promontory facing the Tyrrhenian Sea, between San Saba and Aquarone, along the western coast of Messina ( Fig. 5 ). It has a local distribution restricted to a rocky outcrop constituted by metamorphic marine terraces dating back to the Middle-Upper Pleistocene ( Lentini et al. 2000). From the biogeographical viewpoint, the C. phalacrica population falls within the Peloritan district ( Sciandrello et al. 2015). This district coincides with the north-eastern part of Sicily ( Brullo et al. 1995), which is characterized by the occurrence of several exclusive endemic taxa, such as Adenocarpus commutatus Gussone (1828: 375) , Centaurea tauromenitana Gussone (1844: 512) , Plantago peloritana Lojacono Pojero (1907: 35) , Festuca humifusa Brullo & Guarino (2001: 409) , Centaurea seguenzae (Lacaita) Brullo et al. , Asperula peloritana C. Brullo et al. (2009: 86) , Hieracium hypochoeroides Gibson (1843: 741) subsp. montisscuderii Di Gristina et al. (2013: 50) , Brassica raimondoi Sciandrello et al. (2013: 813) , Silene peloritana C. Brullo et al. (2014: 257) and Vicia brulloi Sciandrello et al. (2019: 59) .

This species grows in the crevices of compact siliceous rocks with northern exposure separated from the shoreline by a narrow sandy belt ( Fig. 6A, D ). In these stands it is quite abundant at altitudes of 20–60 m, together with Jacobaea gibbosa ( Gussone 1821: 71) B. Nordenstam & Greuter (2006: 712) , Dianthus rupicola Bivona (1806: 31) subsp. aeolicus ( Lojacono 1889: 163) Brullo & Minissale (2001: 539) , Hyoseris taurina Martinoli (1953: 257) , Erucastrum virgatum Presl (1826: 94) .

Conservation status: —Based on personal field observations, this species is currently distributed on a very small location of 0.013 km 2. This place, very impervious and relatively inaccessible, is threated prevalently by fire, to which it is periodically subjected. The population is represented by several hundred individuals, often growing in a thickened way, which shows no tendency to extend to neighboring places. According to the method proposed by Gargano (2011) and using the IUCN criteria (also based on monitoring activities carried out for several years by some of the authors, A.C and G.T), Centaurea phalacrica is localized in two grid cells; because of its area of occupancy being less than 10 km 2, it can be assessed as Critically Endangered (CR B2abiii).

Taxonomic notes: —Morphologically, C. phalacrica is closely related to C. aeolica , while it is well-differentiated from the other species belonging to C. cineraria group occurring in Sicily. In particular, this species shares with C. aeolica the leaves tightly laciniate and capitula with phyllaries having short, pale coloured appendages. Conversely, in the other species of this group the leaves are characterized by larger and shorter laciniae, the capitula have phyllaries with well-developed and dark appendages. As concerns C. phalacrica , it differs from C. aeolica in several remarkable characters regarding tomentum, shape, and size of leaves, phyllaries, florets, stamens, style, stigma, achenes, and pappus. Centaurea phalacrica has a whitish-grey tomentum (versus greenish-grey), leaves 1-pinnatisect (versus 1–2- pinnatisect), densely laciniate (versus loosely laciniate), capitula with ca. 80 phyllaries (versus ca. 70), phyllaries 5- nerved (versus 7-nerved), with appendages 2–3 mm long (versus 1–2 mm long), fimbriate with fimbriae 0.2–1.5 mm long (versus denticulate with teeth 0.05–0.3 mm long), ray florets 20–21 mm long, with lobes 8–10 mm long (versus 18–19 mm long, with lobes 4–5.8 mm long), disc florets 19–20 mm long, with lobes 5–5.5 mm long (versus 15–16.5 mm long, with lobes 3.5–4.3 mm long), stamens 20–21 mm long, with anthers 6.5 mm long (versus 16–16.5 mm long, with anthers 6 mm long), style 20 mm long (versus 15 mm long), stigma 3 mm long (versus 2 mm long), achenes 3.8–4 × 1.5–2 mm (versus 3.4–3.7 × 1.4–1.6 mm), pappus with setae 0.2–3 mm long (versus 0.4–2 mm long). Besides, C. phalacrica shows some similarity with C. pandataria mainly in having leaves 1-pinnatisect with laciniae usually wide, more than 2.5 mm, phyllaries 5-nerved, ray florets 20–21 mm long, anthers 6.5 mm long, achenes up to 4 mm long. However, they differ in several features regarding tomentum, leaves, phyllaries, florets, style, stigma, achenes, and pappus. In particular, C. pandataria is characterized by a tomentum more greenish (versus whitish-grey), basal leaves usually lyrate (versus never lyrate), capitula with ca. 60 phyllaries (versus ca. 80 phyllaries), appendages pale brown and blackish at the apex, with 2–5 teeth, 0.1–0.3 mm long, reduced to a single mucro in the innermost phyllaries (versus straw-colored, with 7–15 fimbriae, 0.2–1.5 mm long), disc florets 18 mm long (versus 20–21 mm long), style 18 mm long (versus 20 mm long), stigmate branches 2 mm long (versus 3 mm long), achenes 1.3–1.5 mm wide (versus 1.5–2 mm wide), pappus with setae max 1.5 mm long (versus up to 3 mm long).

Additional specimens examined (paratype): — ITALY. Sicily: Capo Rasocolmo (Messina), tra San Saba e Aquarone , rupi costiere metamorfiche, 38°17’50’’N 15°31’19’’E, 28 June 2020, G. Tavilla s.n. (CAT!) .

Figures

FIGURE 1. Centaurea aeolica. A. Habit. B. Capitulum. C. Appendages of the phyllaries. D. Ray sterile floret. E. Disc fertile florets. F. Stamen. G. Stygma. H. Achenes with pappus. Illustration by S. Brullo based on living material coming from Lipari collected by Tavilla et al. (CAT!).

FIGURE 4. Variability of the phyllaries in Centaurea aeolica (A), Centaurea pandataria (B) and Centaurea phalacrica (C). Illustration by S. Brullo based on living material coming from the same locality as quoted in Fig. 1, 2, 3 (CAT!).

FIGURE 5. Geographical distribution of Centaurea aeolica (blue dots), C. pandataria (red dot) and C. phalacrica (green dot) based on herbarium materials and literature data.

FIGURE 6. Phenological features of Centaurea phalacrica. A. Natural habitat. B. Basal leaves. C. Capitulum. D. Habit. (Photos by S. Cambria).