Centaurea ibn-tattoui M. Chambouleyron, M. Bidat & J.F. Léger, 2014

Chambouleyron, Mathieu, Bidat, Matthieu & Léger, Jean-François, 2014, Centaurea ibn-tattoui (Asteraceae), a new narrow endemic species from northeastern Morocco, Phytotaxa 174 (3), pp. 157-164 : 157-162

Centaurea ibn-tattoui M. Chambouleyron, M. Bidat & J.F. Léger , sp. nov. Figs. 1–5

This new taxon belongs to Centaurea sect. Acrocentron ( Cassini 1826: 37) Candolle (1837: 586) , and is close to five taxa: C. carolipauana Fernández Casas & Susanna (1982: 2) , C. lainzii Fernández Casas (1975: 9) , C. occasus Fernández Casas (1997: 221) , C. prolongoi Boiss. ex Candolle (1838: 303) , endemic to the western Mediterranean Basin, and C. tauromenitana Gussone (1844: 512) , endemic to Sicily. It differs from the latter by it smaller and less lobed leaves, and from the first four by its intermediate and inner involucral bracts with a laciniate, scarious appendage ( Fig. 1 ) which is usually not spiny (except sometimes a short stiff spine on the intermediate bracts, soon deciduous). The involucral bracts appear to be rather variable, as shown in Fig. 1 , but generally with a characteristic large and scarious appendage.

Type: — MOROCCO. Debdou mountains , Province of Guercif , Municipality of Mahirija (more known as Lamrija, locally), at a place called Nif Ziane, on cliffs, elevation 800 m, coordinates ( WGS84 ): N 33.87811° / W 3.39477°, 28 June 2013, M. Chambouleyron s.n. (Holotype: ECWP!, isotypes: RAB!, BC!, P!) .

Diagnosis: —Hemicryptophyte (perennial), 30–70 cm tall. Stems erect, branched. Young plant covered with dense glandulous hairs, quickly disappearing with age (only scarce, short glandulous hairs remain on the leave veins). Stem lanate at petiole insertion of lower leaves. Leaves alternate, green, with a central vein white-yellow to green, margins and sometimes faces scabrid. Basal and lower cauline leaves 10–22 × 1.5–3 cm (including petiole), decreasing in size from base to top, petiolate, lyrate-pinnatipartite or lyrate-pinnatisect, with lobules oblong, lanceolate or ovatelanceolate, with margins entire or sparsely dentate. Upper leaves entire, narrowly lanceolate and sessile. Capitula few, terminal and solitary. Involucre 12–25 × 13–24 mm, globose. Involucral bracts appressed, imbricate, apparently arranged in 6–7 rows, green, gradually increasing in length inwards, inconspicuously veined, glabrous; appendage decurrent, grey-white, scarious, erose, dentate, lacerate or fimbriate, with a central spot dark. Outer involucral bracts 3–4.5 × 2.5–3 mm, with an apical spine ca. 1 mm long; intermediate ones 10–12 × 7–10 mm, sometimes mucronate, or occasionally with an apical spine up to 4 mm long, soon deciduous; inner bracts 16–19 × 3–6 mm, with a proportionally reduced, unarmed appendage. Flowers deep yellow, 16–22 mm long. Achenes greyish-white, 4.3–5.2 × 2–2.4 mm (widest face), compressed, sparsely covered with white, sericeous hairs (0.1–0.3 mm long) on the faces, and with dense hairs 0.5–2 mm long around the insertion areole. Pappus biseriate, the outer whorl of setae 5–7.5 mm long, inequal, brown (sometimes purple in the distal part), the inner one with setae 1–1.5 mm long, white. Flowering: April to June.

Rank: —The differences in morphology of the involucral bracts and leaves, and the geographic isolation from closely related taxa are the criteria that we consider important enough to justify the rank of species for this taxon.

Etymology: —This species is dedicated to our friend and excellent botanist, Dr. Mohamed Ibn Tattou from the Institut Scientifique, Rabat, Morocco, in regard to his major contribution to the knowledge of Moroccan flora.

Ecology: —On calcareous, Jurassic( Medioni1972, 1977),subvertical cliffs,facing north or north-west,at elevations of 800 to 1 400 m. Upper thermo- to mesomediterranean vegetation stages. Arid and semi-arid bioclimates.

This species grows among saxicole taxa: Cheilanthes acrostica , Ephedra fragilis , Rupicapnos africana , Malva subovata , Viola saxifraga , Lobularia maritima subsp. maritima , Sedum sp. , Umbilicus patens , Saxifraga globulifera , Sanguisorba ancistroides , Rhamnus lycioides subsp. oleoides , Polygala rupestris , Micromeria debilis , Teucrium faurei , Linaria tristis subsp. mesatlantica , Chiliadenus rupestris .

Known distribution: —This taxon appears to be endemic to a small area of the Debdou mountains ( Fig. 6 ), pertaining to the biogeographical unit Tell Atlas, Debdou-Mekam (“XX-3”) according to Sauvage & Vindt (1952), or Debdou (“XV-a”) according to Dobignard (1989) and Dobignard et al. (1992). This unit corresponds to the geographical unit “Om-3: Debdou” of Fennane & Ibn Tattou (1998, 2005). The species has been found on three cliffs, with an overall population estimated around 600 individuals.

Conservation status: —According to IUCN criteria ( IUCN 2012) and the present distribution knowledge, this new species should be listed as Vulnerable (VU) because its area of occupancy (A00) is less than 10 km ², with <5 known localities, and number of mature individuals <1000. According to Fennane and Ibn Tattou’s criteria (1998), it should be added to their list of rare, threatened and endemic plants of Morocco as a Very Rare (RR) and Endemic taxon (E), since its known distribution counts less than five localities. However, new prospective effort is needed in northeastern Morocco mountains and Middle Atlas to locate eventual new populations of this species and better evaluate its status and distribution.

Figures

FIGURE 1. Centaurea ibn-tattoui: outer (a–b), intermediate (c–d) and inner (e) involucral bracts, intermediate bract of an immature capitulum (f), variability of intermediate bracts (g–h and i–j).

FIGURE 2. Intermediate bracts of Centaurea prolongoi (a: Fernández Casas 1997), C. occasus (b: López & Devesa 2013), C. lainzii (c: López & Devesa 2013), C. carolipauana (d: González Bueno et al. 1988), C. tauromenitana (e: drawn from P 00044012).

FIGURE 3. Centaurea ibn-tattoui: achene.

FIGURE 4. Centaurea ibn-tattoui: habit.

FIGURE 5. Centaurea ibn-tattoui: flowering capitulum.

FIGURE 6. Locality of Centaurea ibn-tattoui, and prospected area.