Bromus alonsae G. Leofanti & M.L. Echeverría, 2024

Leofanti, Gabriela Agustina, Echeverría, María Lis & Méndez, Alicia López, 2024, A new species of Bromus sect. Ceratochloa (Poaceae: Bromeae) from Argentina, Phytotaxa 669 (1), pp. 47-56 : 51-53

Bromus alonsae G. Leofanti & M.L. Echeverría sp. nov.

( Figs. 2A–E , 3A–H ; Table 1 ).

Type:— ARGENTINA. Buenos Aires, Partido Mar Chiquita, La Caleta , al borde del camino costero, a ambos lados de un canal, 37°46’52.3” S, 57°27’12.4” W, 4 m a.s.l, 4 November 2019, M.L. Echeverría & G.A. Leofanti 229 (holotype BAL! 317 ; isotype BA! ).

The new species, B. alonsae , is similar to B. catharticus var. catharticus but differs in growth habit (perennial with creeping or semi-creeping habit vs. annual or briefly perennial with erect or semi-erect habit), blade color (glaucous green vs. light green), blade pubescence (short and dense vs. variable to glabrous), vernation (folded to rolled vs. rolled), and flowering period (mid-October to late January vs. early September to mid-March).

Description: — Plants perennial, cespitose, with high tiller production, with records up to 81 per plant, and variable vernation, folded or rolled, in the same individual. Culms 20.5–46.5 cm tall, decumbent; nodes 4–8, glabrous to pubescent. Leaf sheaths 5.5–12.5 cm long, usually pubescent, sometimes glabrous, closed for most of their length and open at the upper part; auricles absent; ligules 2–4 mm long ( Fig. 3B ), membranous, apex lacerate; blades 17–35 cm long, glaucous-green, linear, flat, with short dense pubescence. Panicles ( Fig. 3E ) 15.6–25 cm long, loose, elliptic-pyramidal, semi-contracted, with 28–105 spikelets; branches close to the main axis; lower branches 7.2–10.6 cm long and upper branches 2.4–5 cm long; pedicels 0.1–2.1 cm long. Spikelets ( Fig. 3F ) 1.7–3.6 × 0.4–1 cm, ovate-lanceolate, laterally compressed, with 6–10 florets; glumes glabrous, ovate-lanceolate, usually unequal, the upper one 1–3 mm longer than the lower one, persistent, longer than half the length of the lowest lemma, apex acute and keeled; lower glume 0.8–1.5 cm long, 5–8 nerved; upper glume 0.9–1.7 cm long, 7–9 nerved; lemma ( Fig. 3G ) of the basal floret lanceolate, 1.1–2.2 cm long, 7–9 nerved, usually glabrous, apex acute and keeled with sub-apical awn, straight, 0.5–3 mm long, palea ( Fig. 3H ) of the basal floret shorter than the length of the lemma, 0.7–1.3 cm long. Stamens 3. Caryopsis linear-lanceolate. Plants hexaploid, 2n=6x=42.

Phenology:— Flowering and fruiting occur from mid-October to the end of January.

Vernacular name:— “cebadilla de los médanos”, “sand dune brome”

Ecology and distribution:— Populations of the new species are distributed along 160 km of the coastline between the localities of Mar Chiquita (37°44’43.2” S, 57°25’10.7” W) and Quequén (38°33’44” S, 58°37’31.2”W). The species grows on alkaline soils (pH 8.2–8.6) with low organic matter content (0.7–2.4%), and sandy to loamy-sandy texture. It is commonly associated with the exotic species Carpobrotus edulis (Linnaeus 1759: 1060) N. E. Brown (1926: 249) and the native species Poa lanuginosa Poiret (1804: 91) , Panicum racemosum ( Palisot de Beauvois 1812: 168) Sprengel (1824: 313) , Achyrocline saturejoides ( Lamarck 1788: 747) Candolle (1838: 220) , Calystegia soldanella ( Linnaeus 1753: 159) Roemer & Schultes (1819: 184) , Margyricarpus pinnatus ( Lamarck 1785: 567) Kuntze (1898: 77) , and Adesmia incana Vogel (1838: 76) . It grows in sympatry with other species of the genus: B. catharticus var. catharticus , B. auleticus , and B. rigidus .

Etymology:— Dedicated to Botany Professor Sara Isabel Alonso, who encouraged us to investigate and describe this new species to science.

Additional material examined:— Argentina. Buenos Aires. Pdo. Gral Pueyrredón, Playa Escondida , 38°13’32”S, 57°43’27.6” W, 15 m a.s.l., 3 November 2019, M.L. Echeverría 201 (BAL 332) ; Ibidem, Pdo. Gral. Pueyrredón, Playa Chica , 38°1’22.4”S, 57°31’38.6”W, 15 m a.s.l., 7 November 2019, G.A. Leofanti 2 (BAL 358) ; Ibidem, Pdo. Mar Chiquita, La Caleta , 37° 46’ 52.3” S, 57° 27’ 12,5” W, 3 m a.s.l, 4 November 2019, M.L. Echeverría & G.A. Leofanti 228 (BAL 316) ; Ibidem, Pdo. Mar Chiquita, Mar Chiquita , 37°44’45.6”S, 57°25’10.6”W, - 3 m a.s.l, 4 November 2019, M.L. Echeverría & G.A. Leofanti 244 (BAL 371) ; Ibidem, Pdo. Necochea, Costa Bonita , 38°33’43.9”S, 58°37’31.4”W, 11 November 2019, M.L. Echeverría & G. Leofanti 258 (BAL 343) ; Ibidem, Pdo. Necochea, Quequén , 38°33’11.7”S, 58°40’23.9”W, 11 November 2019, M.L. Echeverría 270 & G.A. Leofanti 244 (BAL 390) .

Figures

FIGURE 2. Bromus alonsae. A. Habitat, dunes. B. Habitat, cliff. C. General aspect of the clumps (habit). D. Panicle. E. B. catharticus var. catharticus panicle (arrow in the left) and B. alonsae panicle (arrow in the right). Photos by G.A. Leofanti.

FIGURE 3. Bromus alonsae. A. Habit. B. Ligular region of the leaf. C. Cross section of a leaf blade with folded vernation. D. Cross section of a leaf blade with rolled vernation. E. Panicle. F. Spikelet. G. Basal floret lemma. H. Basal floret palea. Illustrated by N. Russo.