Introduction

The genus Festuca L. (Poaceae, Loliinae) is one of the most critical groups of the European flora. The high level of morphological plasticity within Festuca together with nomenclatural complexity makes its systematic interpretation difficult (Angelov & Ivanova 2012). The number of species fluctuates constantly according to the changing perspectives in the field of systematics. Generally speaking, however, it can be said that Festuca comprises 400–450 species with a cosmopolitan distribution across the temperate regions and mountain areas in the tropics (Clayton & Renvoize 1986; Watson & Dallwitz 1992). The primary centre of diversification of the genus is found in the meadows, alpine grasslands and steppes of Eurasia and N Africa. About 100 taxa (more than 80 species) are found in the Iberian Peninsula, 38 of these taxa endemic to this area, and 13 or so constituting Ibero-Maghrebian endemics (Cebolla & Rivas Ponce 2003; Devesa & al. 2013).

During recent field exploration and study of the vascular flora of the S Catalonian coastal mountain chain and adjacent areas, some plants belonging to the Festuca rubra L. aggregate (F. sect. Aulaxyper Dumort.) came to our attention. These plants were initially equated with F. trichophylla (Ducros ex Gaudin) K. Richt, and presumed to be either that species or the closely related local endemic F. paucispicula Fuente & Sánchez Mata (≡ F. rubra subsp. font-queri Litard.), a seldom-collected plant of disturbed sites in these coastal mountains. However, on closer examination it was discovered that, though superficially similar, these plants possessed sufficient distinguishing characteristics to warrant their recognition as a distinct species.

Going back to July, 2002, living material of this fescue was collected during a field trip to the Ports massif. This material was subsequently cultivated first in the nursery area and then planted out in the Botanic Garden of Barcelona, where its growth has been monitored. In 2014, a further trip to this and the Serra de Cardó, both in the province of Tarragona, was made in order to observe the grass in the field and make a more detailed study of the Festuca material collected there.

In the present contribution, morphological, cytogenetical and ecological data set out below support the description of plants from the Ports mountain area and from the mountains of Cardó and Montsià as belonging to a new species, Festuca dertosensis.

Material and methods

Morphological and anatomical observations were undertaken on herbarium specimens from BC and BCN (herbarium codes according to Thiers [continuously updated]). Representative herbarium material examined is listed in the Appendix. In addition, field observations were made on individuals from several populations of the Ports mountain area and Cardó (including the type locality of Festuca paucispicula).

For the study of leaf anatomy, fully-developed basal (innovation) leaves were rehydrated, sectioned and mounted in water, to be observed under a Nikon stereoscopic zoom microscope.

For the chromosome counts, root tips from plants growing in pots were pretreated in distilled water for 24 h at 4 °C. This material was fixed in a solution of absolute ethanol and glacial acetic acid (3:1) for 30 min in the dark. Subsequently, the material was transferred to a new solution of absolute ethanol and glacial acetic acid (3:1) for 4 h in the dark. After this step, the material was conserved at -20 °C in the same solution. For chromosome counts, root-tip meristems were excised, hydrolysed for 10–12 min on 1NHCl at 60 °C, washed with distilled water, stained with 1% aceto-orcein and squashed on a drop of 9 : 1 45% acetic acid: glycerol. Slides were observed with a Zeiss Axioplan microscope and the best metaphase plates were photographed with an AcioCam-HRm camera.

The DNA 2C-value of three individuals of Festuca dertosensis was estimated using flow cytometry. One plant is from the Creu de Santos population, and the other two from Mont Caro. Pisum sativum ‘Express Long’ (2C = 8.37; Marie & Brown 1993) was used as internal standard. The total nuclear DNA content was calculated by multiplying the known DNA content in Pisum by the quotient between the 2C peak positions of the target species and the internal standard in the histogram of fluorescence intensities. The half peak coefficient of variation (HPCV hereinafter) was calculated for plants and standards in order to test the quality of assessments (see Garnatje & al. 2007 for more details).

Results

Our findings resulting from these morphological and cytological studies lead us to the conclusion that we are faced with a fescue sufficiently distinct to merit its recognition as a new taxon, for which we believe the rank of species to be the most appropriate, and which we describe as follows.

Festuca dertosensis Pyke & L. Sáez, sp. nov. — Fig. 1, 2, 3A–C.

Festuca subg. Festuca sect. Aulaxyper Dumort. Holotype: Spain, Catalonia, Tarragona province, Roquetes municipality, Portell de Caro, 31TBF7722, 1000 m, fissures in calcareous cliffs, 16 Jun 2014, L. Sáez & S. Pyke SBP6977 (BC 879690 [Fig. 1]; isotype: JACA R299666).

Diagnosis — Festuca dertosensis differs from F. paucispicula and F. trichophylla subsp. meridionalis Pyke & Molero in its basal leaf morphology and in the smooth abaxial leaf surface, a feature shared with F. rubra subsp. rubra. The epidermis of these plants lacks the small protuberances characteristic of the F. trichophylla group of species. The internal leaf anatomy, very close to that of F. heterophylla, distinguishes it from the previously-mentioned taxa. In addition, it can be distinguished from F. paucispicula by its glabrous ovaries and from F. heterophylla by its narrow, tightly-infolded cauline leaves, creeping habit and much smaller size.

Description—Chasmophytic grass, perennial, laxly caespitose, spreading, with extravaginal vegetative shoots and thin, diffuse underground stolons or rhizomes that exploit crevices between rocks. Culms (12-)15-25(-30) cm, ascending, smooth, glabrous, weakly striate below panicle. Innovation leaf sheaths at first closed almost to mouth, soon splitting, glabrous or weakly scabrid distally, reddish purple basally, becoming brown when dry and eventually decaying into fibres. Ligules very reduced, without auricles. Cauline leaves like basal ones, but with 5 veins and 3 ridges. Innovation leaf blades 3–15 cm, green or slightly glaucous, flexible, abaxially glabrous, with a ± acute, non-pungent apex; cross-section triangular, square or rhombic, 0.2-0.4(-0.6) mm wide (maximum folded width, sometimes wider in fresh state), with 3(-5) veins; sclerenchyma in 5(-7) strands of approximately equal size; adaxial grooves 2, ridge 1, with long, scattered hairs on adaxial surface; abaxial epidermis smooth, lacking protuberances. Panicles 3-7(-8) cm, with (4 or)5-13(-19) spikelets and 0-2 short branches scabrid on veins. Spikelets 8–10 mm (to apex of 4^th lemma, excluding awns), with 3-5(or 6) florets. Glumes unequal, margin broadly scarious, lower glume 3–4 mm, 1-nerved; upper glume 4–5.5 mm, 3-nerved, lanceolate, acuminate. Lemmas 4.8–6 mm with a thin, scarious margin, 5-nerved, glabrous except at apex, shortly ciliate on margin, with an awn of 1–3 mm. Paleas 5–6 mm, glabrous, with ciliate margin and apex, keels rough. Lodicules 0.9–1.1 mm, deeply indented. Ovary glabrous. Anthers 3.2–3.5 mm.

Fig. 1.

Festuca dertosensis — holotype specimen (BC 879690).

Fig. 2.

Festuca dertosensis - A: habit; B: details of spikelet. — All drawn from the holotype by L. Sáez.

Fig. 3.

Cross-sections of basal leaves with some portions of abaxial epidermis amplified — A–C: Festuca dertosensis; D–F: F. paucispicula; G–I: F. trichophylla subsp. meridionalis. — All drawn by L. Sáez.

Distribution and ecology — Festuca dertosensis is, as far as is known, restricted to the Ports massif and the Cardó and Montsià summit areas (all within the provinces of Tarragona and Castellón) (Fig. 4). The new species is clearly sciophilous and grows in ledges and fissures in limestone cliffs and among rocks (mainly N-facing aspects) between c. 600 m and 1400 m. It is also found on the ground at the foot of cliffs and descends exceptionally via screes to c. 500 m, as testified by the Bolòs sheet from Castellón province (see Appendix). Companion species include Agrostis schleichen Jord. & Verlot, Chaenorhinum crassifolium subsp. cadevallii (O. Bolòs & Vigo) Güemes, Festuca gautieri (Hack.) K. Richt, and the three locally endemic species Aquilegia paui Font Quer, Salix tarraconensis Pau and Thymus willkommii Ronniger.

Etymology — The specific epithet dertosensis derives from Tortosa, in Latin Dertosa, the Roman colony that became an important centre for the Ebro delta and surrounding area.

Leaf anatomy — The epidermal cell structure of Festuca dertosensis conforms to the pattern of F. rubra subsp. rubra, differing from F. trichophylla and its subspecies (Molero & al. 2015) in the absence of minute protuberances, which Al-Bermani & al. (1992) considered a significant unifying feature of their F. trichophylla group. This group is made up of F. nevadensis (Hack.) K. Richt., F. paucispicula, F. rothmaleri (Litard.) Markgr.-Dann. and F. trichophylla with its subspecies, including the plant now referred to as F. iberica (Hack.) K. Richt.

The leaf cross-section (Fig. 3), however, bears a strong resemblance to that of Festuca heterophylla Lam., a plant present in the region, where it grows in the mountains of the Prades area about 50 km from the Cardó site. This differs in being a more robust plant with dimorphic leaves, the basal ones capillary with a very similar cross-section, and the cauline leaves wider and flat in the fresh state. The leaf anatomy of F. dertosensis is also very close to that of F. plicata Hack. (F. sect. Festuca), which, however, is a densely caespitose, intravaginal, saxicolous species, with corrugated basal leaf sheaths, shorter and denser panicles, and awns often as long as the lemmas. This fescue does not seem to have been found further north than the Gúdar massif in the province of Teruel, some 90 km south of the Ports massif.

Comparative morphology — Although related species of the Festuca rubra and F. trichophylla groups can sometimes be found growing on inland cliffs, F. dertosensis is of clear preference a saxicolous species, its roots and slender hypogeal stolons (rhizomes, generally speaking) exploiting the cracks and ledges in the often vertical rock surfaces where it is most commonly found growing.

Fig. 4.

Distribution of Festuca dertosensis. The dots show the known populations

Apart from the method of anchorage and the internal leaf structure, the new taxon can be distinguished from Festuca trichophylla subsp. meridionalis by its smaller size, more diffuse habit, and shorter panicles with few spikelets. These reduced panicles have a parallel in F. paucispicula, which, however, differs in its thicker rhizomes, its shorter, somewhat scabrid leaves with scabrid-pubescent sheaths, and its pubescent ovaries.

A further species from the Festuca trichophylla group, F. iberica, does not appear to be present in the limestone coastal sierras where F. dertosensis is found. Apart from the distinct epidermal protuberances, this Ibero-Maghrebian taxon normally has scabrid leaves and a less spreading, more densely caespitose habit.

Festuca heterophylla and F. heteromalla Pourr. are large, normally terrestrial plants. Festuca dertosensis shares a similar leaf anatomy with the nemoral F. heterophylla, but differs from both species in its much smaller size, its reduced panicles with smaller spikelets, and its narrow, infolded cauline leaves. The pubescent ovary of F. heterophylla is an additional distinguishing feature.

Festuca rubra subsp. rubra and F. rubra subsp. juncea (Hack.) K. Richt, both differ from F. dertosensis in their leaf cross-section, which is not only larger in most cases but also has a distinct polygonal shape, with more veins, sclerenchyma strands and adaxial grooves. Subsp. juncea, probably not present in the mountains of this region, has wider, rush-like leaves (c. 1 mm wide), and subsp. rubra, introduced through agricultural, amenity and land-reclamation activities, is variable, but generally a stronger-growing plant with more consistent leaves. Both have longer, more branched panicles with more numerous spikelets. Subsp. juncea, here considered in its wider sense, which includes subsp. pruinosa (Hack.) Piper, also appears to have been distributed by humans beyond its supposed native range — high European mountains and N coasts of Europe.

Chromosome number and DNA content — Festuca dertosensis shows a chromosome number of 2n = c. 70 and a 2C = 20 pg (population of Caro) and 2C = 19.90 pg (Creu de Santos population), which corresponds to a 2C mean value of 19.95 pg. The HPCV were lower than 3% in all cases (for targeted plants and standards). Counts were made from a large number of root tips taken from four plants: one of these from Creu de Santos (Serra de Cardó) and three from the scattered population below the summit of Mont Caro, one of which is a cultivated plant originating from material collected in 2002, while the other two date back to a 2014 collection. Other decaploid fescues in F. sect. Aulaxyper include F. nevadensis, a high-mountain species, and F. duriotagana Franco & Rocha Afonso, a lowland species related to F. rubra and of a W Iberian Peninsula distribution. These fescues are clearly distinct from our plant.

Discussion

Festuca dertosensis has in the past apparently been taken for two, or probably three, related species. St.-Yves studied plants collected in the area in question between 1917 and 1949, including material collected by Pio Font i Quer (see Appendix), some of which was referred to as “forma inter var. trichophyllam Gaud, et var. genuinam Hack, medium tenens”. He would have included these plants among the “Hispania” references of his rubra (eu-rubra) var. yvesiana R. Lit. et R. Maire” and “var. trichophylla Gaud, subvar. setacea St.-Y.” entries in his Tentamen of Old World fescues (St.-Yves 1927). These at present would correspond to F. iberica and F. trichophylla s.l., respectively. Other material, for example sheet BC 148940, containing material collected by Antoni and Oriol de Bolòs, was interpreted as falling within F. rubra, with no infraspecific epithet. Cadevall (1936) also lumped all similar plants together under the name F. rubra, although in the footnote of this entry he mentioned the race F. trichophylla Ducros, without entering into more details. Font i Quer (1950) evidently equated these plants either with F. trichophylla or, more unlikely, with F. gautieri subsp. scoparia, rather than F. paucispicula, since he clearly stated on page 67, entry 58, that he had been unable to find further plants belonging to this species he himself had discovered (to be named later by Litardière as F. rubra subsp. font-queri), despite revisiting the Font del Oliver area, where he deemed it to have become extinct. He went on to say that “F. rubra L. ssp. eu-rubra Hack, var. trichophylla” grew in the rocky area close to Coll de Cosp, towards the Font del Teix, locality close to that of our recently collected material. He also annotated F. gautieri from the same general area, referring to plants growing in the Creu de Santos (“Creu dels Sants”) at 940 m, and near to the Font del Teix (sub F. pumila Chaix.). Litardière (1945) published the Coll de Cosp (“Cops” in the text) plants under the name “F. rubra subsp. eu-rubra var. yvesiana R. Lit. et Maire”. The specimen from this locality with his annotations, sheet BC 93049, “var. trichophylla fa. ad var. yvesiana” corresponds, in our understanding, to the new species. In the same paper he published I. rubra subsp. font-queri. Evidently, he considered these plants to be two distinct taxa. Bolòs & Vigo (2001), clearly influenced by Litardière's herbarium notes, equated the populations with F. rubra subsp. yvesiana, a combination made by these authors to accommodate these and other fescues of the region that could not easily be attributed to other close taxa. Royo & al. (2010) made a general reference to subsp. yvesiana, as well as mentioning subsp. font-queri in a text accompanied by a photograph of two herbarium specimens determined as such (Mont Caro, near summit, BF7520, 1400 m, 4 Jul 2009, S. Pyke SBP6247, Museu d'Amposta, Tarragona, sub F. paucispicula) but not subsequently studied. Over the years, several people, including the first of the authors of this paper, have taken the more frequently occurring saxicolous plant for the species at present known as F. paucispicula, but when the leaf anatomy and flowering material with sufficiently developed ovaries was studied, it became clear that they could not be attributed to this taxon. The new species is rather a shy flowerer, producing few fertile culms per plant, and it has not been easy to observe these details in some cases. Festuca paucispicula can look very similar. However, despite the superficial similarities, the anatomical differences (particularly the minute protuberances and generally dispersed prickle-cells of the epidermis, the 5-veined basal leaves and the pubescent ovary) lead us to consider the two as being distinct though sympatric species. The leaf sheaths are variable on specimens of both taxa, those of F. dertosensis being usually glabrous, and those of F. paucispicula being somewhat more pubescent, as observed by De la Fuente & Sánchez-Mata (1986). This value, however, appears to be inconsistent, and the limited material available of the latter species (we have consulted three sheets, from two localities) prevents us from getting a better picture.

What remains clear is that the true Festuca paucispicula is a rare plant consisting of scattered individuals or small groups, in all probability endangered, whereas F. dertosensis is locally abundant close to the summits of both Cardó and Mont Caro, with smaller colonies or isolated individuals in shaded places of the wider area, and does not appear to be endangered. The new taxon grows mainly on cliffs and among rocks, whereas F. paucispicula, from what we can deduce at present, is found in disturbed mountain pastures, anchoring itself by means of its thicker rhizomes to clay or stony soil and thereby helping to fix it.

Although we could not determine accurately the number of chromosomes of Festuca dertosensis, the amount of nuclear DNA suggests that this species is decaploid. After consultation of several studies related to DNA amount and chromosome numbers (Rice & al. 2015), we can affirm that a 2C value of c. 20 pg corresponds to 70 chromosomes. The diploid species of Festuca present 2C values ranging between c. 1.5 and 3.5 pg; this means about 2 pg corresponding to 1 Cx value, so this allows us to infer the ploidy level. Further fieldwork is required before we can provide karyological data for F. paucispicula.

Table 1.

Main distinctive morphological characters of Festuca dertosensis, F. heterophylla, F. paucispicula, F. rubra subsp. rubra and F. trichophylla subsp. meridionalis. Only basal (innovation) leaves were compared (cauline leaves are excluded from this table). “Leaf width” refers to maximum diameter of dry, infolded leaves. Material studied, including type specimens, is detailed in the Appendix.