Centaurea achilleifolia Homrani-Bakali & Susanna 2022, sp. nov.
Creators: name: Bakali, A. Homrani
name: Susanna, A.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Asterales
Asteraceae
Centaurea
Centaurea achilleifolia

description: Centaurea achilleifolia Homrani-Bakali & Susanna, sp. nov. (Figs. 1–4)
Diagnosis
This new taxon belongs to Centaurea sect. Melanoloma and is close to C. atlantis Maire & Weiller in Maire (1940: 24), the only species from the section with subpalmate bracts and achene with pappus. It differs from all the species of C. sect. Melanoloma that occurred in Morocco by the peculiar bipinnatisect small leaves with folded glandular lobes (versus pinnatipartite to pinnatifid for all other species). Furthermore, it also differs from C. atlantis by the small size of the achenes (Tab. 1).
Description
Perennial caespitose, rosulate, unarmed, multicaulescent glandular herb, bright or lime green. Base of the stems fibrous and woody, often covered with remains of some old leaves. Rosette leaves oblong, with thickened petiole, limb bipinnatisect up to 5 cm long and 1 cm wide, decreasing in size inwards, pubescent with simple long trichomes mostly in rachis, simple conic trichomes at the end of almost each lobe (leaflets) and abundant sessile glands especially in adaxial part clumping sand (less abundant in abaxial part); 3–12 (14) lateral lobes or segments pairs (pinna) oblong to lanceolate, lobate, 1-3 pinnatifid (usually trifid in middle part of the limb), small lobes (leaflets) (0.1–0.2 × 0.1–0.4 mm) inclined, folded in the adaxial part with narrowly undulated round margin, almost all segments mucronate with a small conic mucro 0.2–0.5 mm long; terminal lobe ovate-oblong folded also mucronate with a conic mucro. Capitula solitary in the center of the rosettes on a small peduncle (<5 mm); involucre ovoid to subconic 12–16 × 7–12 mm; outer florets neutral, central ones hermaphrodite; involucral bracts imbricate, apparently arranged in 7–9 rows, greenish, gradually increasing in length inwards; appendages of the middle bracts glabrous, with scarious margin, reflexed subpalmate strigose apical appendage, with 6–12 divergent soft spines; middle spine usually longer (up to 3,5 mm), inner bracts narrower, shortly eroded, fimbriate at the apex. Corolla of hermaphrodite florets 13–21 mm long, yellow to orange, limb 7–8 mm long, whitish at the base and yellow to orange towards the apex, with 5 lobes, lanceolate, sparsely glandular; stamens with papillose filaments, anthers 5–6 mm long, creamy yellow. Style yellowish with stigma branches separated at the apex. Achenes pappose, white to brown, 2.5–4 × 1.1–1.6 mm, columnar-ovoid, compressed, elliptical in section, laxly covered with white hairs (0.1–0.2 mm long) on both faces; pappus biseriate, persistent, outer row 1.5–2 mm long, barbellate-scabrid, white, inner row 0.2–1 mm long. Flowers from July to August.
Type:— MOROCCO. Bou Naceur mountains, Province of Guercif, rural commune of Berkine, east of Bou Naceur mountain (southeast exposition till the east summit), elevation 2750 m, coordinates (WGS84): 33°35’28.66”N, 3°50’16.69”W, July 2021, A. Homrani-Bakali (Holotype: RAB-113323; Fig. 1).
Eponymy: —The specific epithet refers to the form of leaves that look like leaves of some Achillea species.
Distribution and ecology:— Centaurea achilleifolia occurs on the summit of Jbel Bou Naceur mountains (3340 m) in Guercif Province, Morocco (Fig. 5). It grows basically on the southeast exposition, beside marl-limestone Jurassic rocks (Delcaillau et al. 2007) at elevations of 2700–2800 m. This massif represents a real backbone of the Middle Atlas and it is subject to oceanic and continental influences; the study of the distribution of its vegetation is particularly interesting. Some other endemic plants that occurred in the area are Artemisia flahaultii Emb. & Maire, Artemisia negrei Ouyahya, Asperula aristata L. f, Astragalus ibrahimianus Maire, Draba hispanica Boiss. subsp. hispanica, Globularia liouvillei Jahand. & Maire subsp. liouvillei, Marrubium multibracteatum Humbert & Maire subsp. multibracteatum, Nepeta nepetella subsp. amethystina (Poir.) Briq., Potentilla caulescens subsp. mesatlantica (Maire) Chambouleyron, Dobignard & J. F. Léger, Scorzonera caespitosa Pomel, Sideritis incana subsp. matris-filiae (Emb. & Maire) Fennane, Silene ayachica Humbert, Silene mesatlantica Maire, Teucrium musimonum Humbert, Thymus atlanticus (Ball) Roussine subsp. atlanticus, Thymus willdenowii Boiss, Vella mairei Humbert, Viola saxifraga Maire.
The climate is typically Mediterranean, the Bou Naceur summit receives between 1200 and 1500 mm. The Climate at the top of Bou Naceur is humid semi-continental and very cold (Taleb, 1992).
Known distribution:—The species appears to be endemic to southeast side of the summit of Bou Naceur mountains (Fig. 5), Middle Atlas. This territory corresponds to the geographical unit “MA-2: Oriental Middle Atlas” of Fennane (2016). The overall population we counted exceeds 50 individuals.
Conservation:—Populations of C. achilleifolia are strictly limited to specific ecological conditions of Bou Naceur mountain. This population is naturally protected from overgrazing by its growing habit on an abrupt slope (the opposite exposition should be on nomadic passages). However, more inspections should be done to circumscribe the distribution of the species.
description: Published as part of Bakali, A. Homrani & Susanna, A., 2022, Centaurea achilleifolia (Asteraceae), a new endemic species from the Oriental Middle Atlas of Morocco, pp. 83-89 in Phytotaxa 542 (1) on pages 84-87, DOI: 10.11646/phytotaxa.542.1.7, http://zenodo.org/record/6404626