Agrostula P.M. Peterson, Romasch., Soreng & Sylvester, 2020

Peterson, Paul M., Sylvester, Steven P., Romaschenko, Konstantin, Soreng, Robert J., Barbera, Patricia, Quintanar, Alejandro & Aedo, Carlos, 2020, A phylogeny of species near Agrostis supporting the recognition of two new genera, Agrostula and Alpagrostis (Poaceae, Pooideae, Agrostidinae) from Europe, PhytoKeys 167, pp. 57-82 : 57

publication ID

https://dx.doi.org/10.3897/phytokeys.167.55171

persistent identifier

https://treatment.plazi.org/id/4C2FE805-65B8-59BC-BF12-5B3287C017EA

treatment provided by

PhytoKeys by Pensoft

scientific name

Agrostula P.M. Peterson, Romasch., Soreng & Sylvester
status

gen. nov.

Agrostula P.M. Peterson, Romasch., Soreng & Sylvester gen. nov.

Type.

Agrostis truncatula Parl.

Diagnosis.

The one species of Agrostula differs from all other species of Agrostis by its glumes being dorsally rounded, not keeled, smooth throughout, and with apices blunt to truncate and erose to denticulate. Further differentiation can be made by the combination of perennial habit, leaf blades with pillars of sclerenchyma that are continuous between the adaxial and abaxial surface of the blades, panicles open and diffuse, florets ½ the length of the glumes, lemmas equally wide as long, widest at (or near) apex, apices broadly truncate, irregularly 5 to 7 denticulate to erose, awnless, paleas c. ½ the length of the lemma, anthers longer than the lemma, caryopsis surface rugose-papillose, and its ecology, being found growing in very shallow soils.

Description.

Perennials moderately to densely tufted. Culms 10-40 cm tall, erect, arching, or geniculate-ascendant, slender, smooth, usually with 3 or 4 nodes extended above the basal foliage. Tillers intravaginal, extravaginal innovations absent. Leaves mostly basal, in fascicles of few to many leaves; sheaths often as long as or sometimes longer than the internodes, glabrous, smooth; ligules 0.5-4 mm long, longer than they are wide in subsp. truncatula and shorter than they are wide in subsp. durieui , oblong, hyaline, glabrous, smooth, apices truncate to acute, dentate; basal and tiller ligules 0.5-2.5 × 1-2.5 mm; upper culm ligules 3-4 × 1-2.5 mm in subsp. truncatula; blades flat, conduplicate, or convolute, straight to sometimes recurved after flowering, acute, firm to rigid, glabrous, abaxially scabrous, adaxially scabrous; blades of lower culm and tillers 3-7 cm long, 0.7-2 mm in diameter as flat, folded or rolled; blades of upper culm 1-4 cm long, 0.5-1.2 mm in diameter as flat, folded or rolled. Inflorescence c. 2-20 × 2-12 cm, a panicle, diffuse and open, broadly ovoid; panicle branches divaricate, capillaceous, with spikelets present only in the distal 1/3- ½, glabrous, smooth; pedicels generally twice as long as the spikelets or longer, thickened, apices clavate, glabrous, smooth. Spikelets 1-1.7 mm long, 1-flowered, disarticulating above the glumes, dorsally compressed or very weakly laterally compressed; glumes equal or subequal, ovoid-lanceolate, membranous, 1-veined, the vein inconspicuous, dorsally rounded, smooth throughout, apices truncate to blunt and minutely notched, erose to denticulate; floret c. ½ the length of the glumes, sessile; lemmas 0.5-0.8 mm long in subsp. truncatula and (0.7-)0.9-1(-1.2) mm long in subsp. durieui , broadly ovoid, equally wide as long, widest at (or near) apex, membranous, dorsally rounded, 5-veined, veins usually evident to distinct, with at least the outer veins excurrent, usually glabrous or sometimes pubescent, smooth throughout, apex broadly truncate and denticulate, with the veins terminating in 5 to 7 teeth 1/8-1/5 the length of the lemma, awnless; paleas 0.3-0.5 mm long, c. ½ the length of the lemma, glabrous, smooth, apices bifid, denticulate; calluses rounded, blunt, glabrous or almost so, abaxially smooth; rachilla prolongation absent. Flowers perfect; lodicules 0.1-0.3 mm long, c. ½ as long as the palea, 2 in number, acute; anthers 0.7-1 mm long, 3 in number; ovaries glabrous. Caryopses 0.8-1.1 mm long, generally longer than the lemmas, only partially concealed at maturity, ellipsoid, surface rugose-papillose, ventrally sulcate, sulcus distinct, almost without rostellum; hilum narrowly elliptic c. 1/6-1/3 the length of the caryopsis; endosperm liquid. 2 n = 14 + 0-4B ( Garde 1951; Björkman 1960; Fernandes and Queiros 1969; Queiros 1974, 1979; Romero García and Blanca López 1988).

Distribution and ecology.

Iberian Peninsula and northern Africa, distributed in France, Spain, Portugal, and Morocco. Found in Mediterranean, Iberian-Atlantic and cold temperate, often high-elevation, environments of the Pyrenees. Forms part of pioneer grassland species assemblages which grow on very shallow and sandy ‘skeleton’ soils, apparently reliant on climatic humidity in addition to precipitation for its water supply. Usually flowering from June to July.

Notes.

Agrostula truncatula also differs in its leaf blade anatomy from most other species of Agrostis in having pillars of sclerenchyma which are continuous between the adaxial and abaxial surface of the blades. These continuous pillars of sclerenchyma are exceptionally thick and found only on the margins and central vein in subsp. truncatula, while subsp. durieui has thinner continuous sclerenchyma packets in the margins, central and primary veins ( Romero García and Blanca López 1988: fig. 4C-F). Costal cells and intercostal long cells of the abaxial blade surface are also distinct, with A. truncatula differing from species of Agrostis in the Iberian Peninsula in having paired s0-z cells in the costal zone, and l3 type long cells in the intercostal zone ( Romero García and Blanca López 1988). Stomata are also apparently absent on the abaxial blade surface, a character found in only a few other species in the Iberian Peninsula, i.e., Agrostis reuteri and Alpagrostis setacea (Romero García & Blanca López, 1988).

Kingdom

Plantae

Phylum

Tracheophyta

Class

Liliopsida

Order

Poales

Family

Poaceae