Festuca silana Ardenghi, Pallanza & Foggi, 2025

Pallanza, Mattia, Orsenigo, Simone, Ardenghi, Nicola Maria Giuseppe, Bernardo, Liliana, Šmarda, Petr, Šarhanová, Petra, Rossi, Graziano & Foggi, Bruno, 2025, Festuca silana (Poaceae), a new species from the Sila plateau in Italy, PhytoKeys 255, pp. 85-102 : 85-102

Festuca silana Ardenghi, Pallanza & Foggi sp. nov

Typus.

Italy • Sila piccola, Zagarise (Catanzaro), Latteria, Lato W del sentiero, Pendici SW del M. Gariglione (WGS 84: 39°07'29.4"N, 16°37'32.8"E), 1587 m, prateria meso-xerofila con roccia granitica affiorante, assieme a Patzkea paniculata , 06.07.2014, N. Ardenghi & L. Bernardo. (holotype: PAV-150000 !; isotypes: FI!, CLU!, W!, G!) .

Italy • Sila grande, Spezzano della Sila (CS), Vaccarizzo, Sponda S del Lago Cecita (WGS 84: 39°22'13.5"N, 16°30'40.1"E), 1150 m, prato arido con Astragalus parnassi subsp. clabricus , su sabbie granitiche con affioramenti rocciosi, 05.07.2023, M. Pallanza & L. Bernardo. (paratypes: PAV-150002 !, PAV-150003 !, FI!, CLU!, W!, G!) .

Italy • Sila grande, Casali del Manco (CS), Lago Ariamacina, Sponda N del lago (WGS 84: 39°20'00.8"N, 16°32'39.0"E), 1327 m, prato arido con Astragalus parnassi subsp. clabricus , su sabbie granitiche, 05.07.2023, M. Pallanza & L. Bernardo. (paratypes: FI!, CLU!, W!, G!) .

Italy • Sila grande, San Giovanni in Fiore (CS), Carlomagno, A W della SP 211 (WGS 84: 39°16'58.1"N, 16°32'36.1"E), 1535 m, prato mesofilo a Patzkea paniculata , su substrato granitico con spesso strato di suolo, 05.07.2023, M. Pallanza & L. Bernardo. (paratypes: PAV-150001 !, FI!, CLU!, W!, G!) .

Description.

Perennial herb, caespitose to densely caespitose, occasionally pruinose. Tiller shoots intravaginal. Culms (32.0 –) 44.7–57.2 (– 69.5) cm long and (0.52 –) 0.77–1.04 (– 1.29) mm in diameter, erect cylindrical, canaliculated, smooth to the touch, with 1 (– 2) visible nodes, dark brown to black in color, located in its lower third. Cauline leaves 1 (– 2), (1.6 –) 2.6–4.0 (– 5.3) cm long, sheathing the culm for (5.8 –) 8.0–10.3 (– 12.8) cm. Basal leaf sheath glabrous, on extremely rare occasions with few sparse hairs, open down to the base, yellowish in color, more rarely veined in red. Ligula 0.5–0.8 mm long, membranaceous, truncate, fringed, with two auricles at the sides. Basal leaf blade (7 –) 11.8–21.6 (– 31.7) cm long and (0.75 –) 0.94–1.06 (– 1.36) mm in diameter, smooth, somewhat rigid, conduplicate, bright to dark green. Cross section outline in an open U-V shape. Subepidermal sclerenchyma organized in 3 main strands located at the margins and keel of the leaf blade, thickened and often decurrent or accompanied by secondary strands opposing vascular bundles, forming an interrupted or irregular complete ring. Vascular bundles 7 (– 9). Ribs 2 (– 4). Abaxial surface of the leaf blade covered with a dense indumentum of (0.03 –) 0.04–0.07 (– 0.13) mm long hairs. Adaxial surface smooth, with small undulations between epidermal cells. Panicle (4 –) 6.4–8.6 (– 12.5) cm long, cylindrical to pyramidal during anthesis, dense, with 7–27 spikelets; branches 1–5, simple, antrorsely scabrid; nodes 7–12. Spikelets (6.24 –) 7.33–8.13 (– 8.87) long, laterally flattened, elliptic, green, with (3 –) 4–6 (– 8) fertile florets. Glumes 2, unequal, lanceolate, glabrous or rarely with few sparse hairs on the margins and apex. Lower glume (2.21 –) 2.55–3.12 (– 3.90) mm long, with a single nerve. Upper glume (2.46 –) 3.68–4.31 (– 5.12) mm long, 3 - nerved. Lemma (3.82 –) 4.81–5.26 (– 5.83) mm long, lanceolate, glabrous or more rarely with few sparse hairs near the apex, terminating in an apical awn (1.23 –) 1.83–2.52 (– 3.30) mm long. Palea 4.53–5.71 mm long, lanceolate, bifid, with 2 finely dentated keels. Anthers 3, (1.72 –) 2–2.44 (– 2.93) mm long, yellow to orange in color. Ovary glabrous. Stygmas 2, with a feather-like shape. Lodicules 2, bilobed, 0.83–1.06 mm long. Caryopsis 2.42–3.85 mm long, brown to dark orange at maturity, adherent to the palea (Fig. 4 ). Somatic chromosomes 42 (2 n = 6 x).

Eponym.

The new species is named after the Sila plateau where it typically occurs.

Diagnosis.

Differt a Festuca costei (St. - Yves ex Litard.) Markgr. - Dann. crassiore sclerenchyma in laminarum margine et carina, plerumque 7 (non (7 –) 9–11) fasciculis vascularibus, densioribus et longioribus trichomatibus in abaxiale superficie, minutis undulationibus inter epidermidis cellulas, 42 (non 28) chromosomatibus.

It differs from Festuca costei (St. - Yves ex Litard.) Markgr. - Dann. for the thicker sclerenchyma at margins and keel of the leaves, vascular bundles are rarely more than 7 (compared to the (7 –) 9–11 in F. costei ). Abaxial indumentum is more dense and with longer trichomes compared to F. costei . It also presents small undulations between epidermal cells. Somatic chromosomes 2 n = 6 x = 42 instead of 2 n = 4 x = 28 in F. costei .

Differt a Festuca marginata (Hack.) K. Richt. sclerenchyma plerumque decurrente vel completum anulum fingente potius quam in tribus discretis filis ordinato, fasciculis vascularibus raro plus quam 7 (non (7 -) 9–11 ut solet in F. marginata ), longioribus trichomatibus in densiore abaxiale superficie, longioribus aristis, undulationibus inter epidermidis cellulas, 42 chromosomatibus, non 14.

It differs from Festuca marginata (Hack.) K. Richt. in the sclerenchyma, usually decurrent or up to forming a complete ring instead of being organized in three discrete strands. Vascular bundles are rarely more than 7 (compared to the (7 –) 9–11 in F. marginata ). Abaxial indumentum is richer and with longer trichomes compared to F. marginata . Awns longer compared to F. marginata . Undulations are present in between epidermal cells. Somatic chromosomes 2 n = 6 x = 42 instead of 2 n = 2 x = 14 in F. marginata .

Differt a Festuca trachyphylla (Hack.) R. P. Murray sclerenchyma prope margines et carinam crassiore; foliis numquam scabris et colore viridi clariore (non glauco ut solet in F. trachyphylla ); spiculis numquam pubescentibus; foliarum vaginis quam saepissime glabris (non pubescentibus ut solet in F. trachyphylla ).

It differs from Festuca trachyphylla (Hack.) R. P. Murray in the sclerenchyma, thicker in the correspondence of margins and keel, the leaf blades never scabrid and of a brighter green color (opposed to the glaucus of F. trachyphylla ). Spikelets are never pubescent. Leaf sheaths are glabrous except for extremely rare exceptions (opposed to the commonly pubescent in F. trachyphylla ).

Distribution and ecology.

The species is only known from the Sila highland, currently from 13 populations (Fig. 5 ). It mainly grows in grassland and pasture communities (Anthemidetalia calabricae Brullo, Scelsi & Spampinato, 2001) on granitic sands in xerophilic to mesophilic conditions at altitudes between 1100 m and 1600 m. F. silana typically occurs in grasslands of xerophile to mesophile conditions, along with other Festuca taxa such as F. marginata subsp. marginata , F. trachyphylla , F. rubra subsp. commutata and F. cyrnea .

Conservation status.

Although the plant has a distribution limited to the Sila plateau, it is one of the dominant species in the grasslands that it inhabits and lacks any particular threat that could cause a decline in the population. Therefore, it had to be considered as Least Concern (LC) according to IUCN (2012).

Figures

Figure 4. Illustration of Festuca silana Pallanza, Ardenghi & Foggi based on the specimens from the locus classicus A overall habitus and morphology of the species B detailed appearance of the spikelet C detailed view of lemma and palea D 1 leaf cross-section of the holotype D 2 – D 5 different leaves cross-sections showcasing intraspecific variability.

Figure 5. Map of the Sila and known stations of F. silana occurring within the plateau.