Centaurea stuessyi Arnelas, Devesa & E. López, 2013

Arnelas, Itziar, Devesa, Juan Antonio & López, Eusebio, 2013, Centaurea stuessyi (Compositae: Cardueae), a new species from the eastern Iberian Peninsula, Phytotaxa 115 (2), pp. 42-48 : 43-44

Centaurea stuessyi Arnelas, Devesa & E. López , sp. nov. ( Fig. 1)

Type: — SPAIN. Tarragona : Rasquera, Balneario de Cardó, 479 m, 1 Jul 2009, I. Arnelas Seco 27/09 (holotype COFC 57443 !) .

Perennial, multi-stemmed. Lower leaves linear-spathulate or narrowly oblong-spathulate, with margins revolute and scabrid, the rest linear. Capitula discoid. Involucre (13)15–18(21) × 5–8(10) mm, ± ovoid; involucral bracts with a linear-subulate appendage, pectinate-fimbriate, recurved or reflexed. Appendage of the middle bracts (2.5)3–4.5(6) × 0.3–0.5 mm, with (1)6–8 pairs of fimbriae (0.5) 1–2.5 mm long. Corolla 13– 15(19) mm long. Stamens with uniformly pilose filament; anthers 5–7 mm long. Achenes 3.5–4.5(5) × 1.3– 1.8 mm, cylindrical or oblong-obovoid, loosely pubescent. Pappus double, persistent, the outer with 2–3 rows of paleae 0.5–1.5(2.5) mm long. Pollen polar axis 43.8± 1.8 µm, equatorial axis 38.25± 1.9 µm.

Distribution and ecology: — Centaurea stuessyi is endemic to NE Spain (Castellón, Tarragona and Teruel provinces) ( Fig. 2 ). This species is growing on rocky hillsides on limestone, dolomite, and gypsum, at elevations of 320–980 m, flowering from April to June.

Etymology: —The name of the species honors the American botanist Tod F. Stuessy, a great expert on Asteraceae .

Additional specimens examined (paratypes): — SPAIN. Castellón : Morella ( Els Ports ), Mas de Garró road, near Barranc de Torre Miró, 26 Jul 1988, Aguilella, Riera & Baeza ( VAL 167646 , 167647 & 167648) ; La Puebla de Alcolea , 30 Jun 2009, Arnelas ( COFC 58133 ) ; Roca del Falcó , Zorita del Maestrazgo, 5 Jun 1990, Laguna ( VAL 72748) . Tarragona : Arens de Lledó, 1 Jul 2009, Arnelas ( COFC 58131 ) ; Arnés , valle del río Algás, 5 Jun 1991, Mateo ( VAL 74251) ; Bot , 1 Jul 2009, Arnelas ( COFC 58134 ) ; Calaceite , 7 Jul 1919, Rubió ( BC 34499 ) ; Horta de Sant Joan , Natural Park of El Port, road to Les Roques de Benet, 1 Jul 2009, Arnelas ( COFC 58132 ) ; Rasquera , balneario de Cardó, 1 Jul 2009, Arnelas ( COFC 57443 ) ; Roca Foradada , 6 May 1942, Font Quer ( BC 92952 ) ; Serra de Montsiá Ulldecona , 13 Jun 1916 Font Quer ( MA 134621) ; Ulldemolins , without date, Batalla ( BC 141320) . Teruel : Aguaviva, near La Peña de Alicante, 13 Jul 1981, Aguilella ( VAL 13076) ; idem, Jul 1981, Aguilella & Mateo ( VAL 187705 ) ; Arens de Lledó , 28 May 1989, Mateo ( VAL 64468) ; Calaceite , 14 Sep 2008, Arnelas ( COFC 58946 ) ; idem, valley of Algás , to Caseres, 27 Apr 1996, Mateo, Fabregat & Lopez Udias ( VAL 97159) ; Mazaleón , valley of Matarraña, to Maella, 27 Apr 1996, Mateo, Fabregat & Lopez Udias ( VAL 97158) ; Torre de Arcas , 26 Jun 1988, Mateo ( VAL 59041) .

Discussion: — Centaurea stuessyi is an endemic species located in the mountains of the Teruel and Tarragona provinces (NE Iberian Peninsula). Table 1 shows the main quantitative and qualitative characters to differentiate the new species and the most closely related allies: C. antennata s. l. and C. linifolia , the species occurring in the Castellón, Tarragona and Teruel provinces ( Fig. 2 ). Centaurea stuessyi differs from C. antennata s. l. in having basal leaves oblong-spathulate, linear-spathulate or linear, and from C. linifolia in having discoid capitula. Our chromosome study indicated that the new species has a different chromosome number. In the two populations studied, this was found to be 2 n = 44, unlike the 2 n = 22 presented by C. antennata and C. linifolia (vide Arnelas & Devesa 2010). The chromosome number 2 n = 44 reported by Gardou (1972) for C. linifolia may belong to the new NR tetraploid species. Regrettably it was not possible to examine the voucher specimen of this report and to confirm the presence of plants of this floral morphotype in the province of Barcelona. Furthermore, in accordance with other authors (e.g. Gould 1957) the pollen of these discoid plants with tetraploid chromosomes is larger in size ( Table 1). From the material gathered in the several collecting campaigns conducted during the years 2007–2009 and the study of herbarium material, it is inferred that the new species is confined to a very specific area that coincides with the area of overlap of C. linifolia and C. antennata subsp. antennata ( Fig. 2 ). In no case did we observe populations with plants of an intermediate type between the two floral morphs. Furthermore, the morphological and geographical differentiation is also supported by the molecular analysis carried out by Arnelas (unpublished data). Particularly, AFLP multilocus analysis showed the genetic proximity of the new taxon to C. antennata subsp. antennata and C. linifolia suggesting the possible hybrid origin of C. stuessyi ; however, the results of Bayesian analysis showed genetic differentiation of the new taxa from its putative parents C. antennata subsp. antennata and C. linifolia . This result is corroborated by a recent nuclear sequence study in the cited species showing a clear separation of the new species from its relatives (Arnelas, unpublished data).

Chromosome number: —The chromosome study was performed on plants of two populations of C. stuessyi (Castellón, COFC 58133; Tarragona, COFC 57443), in both cases on somatic metaphases of root meristems. The roots were treated with an antimitotic – 0.002 M 8-hydroxyquinoline ( Tjio & Levan 1950) – for 4 hours, and then were fixed and preserved in a mixture of absolute alcohol and ferric acetate (3:1) ready for staining with alcoholic acetic-carmine ( Snow 1963) for not more than 24 h. For imaging, we used a Moticam 2000 digital camera mounted on a Mootic BA300 microscope. The present count in the two studied populations of C. stuessyi indicates the same chromosome number: 2 n = 44.

Palynology: —The pollen characteristics were studied from pollen grains of pre-anthesis capitula obtained from natural populations or herbarium sheets. The grains were cleaned by the acetolysis method described by Erdtman (1960) and modified by Hideux (1972). All the samples are preserved in the University of Cordoba's Pollen Collection. The study was carried out in 7 populations of C. antennata subsp. antennata (voucher VAL 165297), C. antennata subsp. meridionalis (vouchers MA 408934 and MA 541884), C. linifolia (vouchers COFC 57478, COFC 57479 and COFC 58491) and in the new species (voucher VAL 97158). Measurements were made in 20 grains for each population. The results obtained from the pollen study indicated that the pollen of tetraploid plants with discoid capitula are larger in size than that of C. linifolia and of C. antennata s. l. ( Table 1).

Figures

FIGURE 2. Distribution ranges of Centaurea antennata (subsp. antennata and subsp. meridionalis), C. linifolia and C. stuessyi.