Bromus brevis, is a species of brome grass endemic also known by the common names pampus brome (English), cebadilla pampeana and cebadilla de la sierra (Spanish - Argentina), and by the indigenous name lanku kachu (Ranquel).[2][3][4][5] It was described by German botanist and zoologist Christian Gottfried Daniel Nees von Esenbeck in 1854 in Synopsis plantarum glumacearum.[6]
It is endemic to central and southwest Argentina, and introduced and naturalised in New Zealand and Australia.[7][1]
B. brevis is one of several species in the Bromus catharticus complex within the Bromus section Ceratochloa, all of which are hexaploids with the chromosome count 2n=42.[8]
Description
Bromus brevis is an annual to perennial grass with short, stiffly erect narrow, pubescent-leaved tufts, up to 30-75cm. It usually has short panicle inflorescences (8-15cm), born on erect culms. Spikelets are 1-2 cm, ovate-oblong, with light bicoloured yellowish-green florets. Lemmas are 7-9-nerved, with very short, silky, appressed hairs, and are awnless, mucronate, or have short awns (0.5-0.8mm).[5][6]
The distribution of Bromus brevis overlaps entirely with Bromus catharticus. From that species, it can be distinguished by its compact spikelet borne on short pedicels (1.5-5 mm long), on erect panicles. Spikelets are 9-24 mm long, often have awnless or mucronate lemmas, or have awns shorter than 3 mm.[9]
In Australia, B. brevis is found in the Northern, Central, and Southern Tablelands, as well as the North-Western and Central-Western Slopes, and in Eastern Tasmania.[15]
Habitat
Bromus brevis is a xeric plant (a plant that grows in dry habitats) from 0-2600 m.a.s.l, often found on sandy riverbanks and slopes. It is sometimes found on forest margins and permanent polyphytic meadows in the semi-arid Pampas and Puna grasslands.[16][17]
In New Zealand, its habitat is described as roadsides and waste ground.[5] Similarly, in Australia it is described as growing in disturbed areas, especially on granitic soils.[18]
B. brevis is one of several species in the Bromus catharticus complex within the Bromus section Ceratochloa, all of which are hexaploids with the chromosome count 2n=42.[8] A 1985 study produced an allodecaploid hybrid between B. catharticus and B. brevis, which had one basic, highly homologous genome, which formed up to 7 quadrivalents. This suggests that both species are allopolyploids.[21]
Breeding system
Like most species in Bromus section Ceratochloa, B. brevis flowers both through chasmogamy (outcrossing through open flowers) and cleistogamy (self-pollinating through closed flowers), with each kind of flower existing on the same spikelet.[22]
B. brevis maintains very high levels of fertility through selfing, with 91% of cleistogamous flowers producing seeds.[22]
Phenology
B. brevis can be annual, biennial, or perennial depending on conditions.[23][24] In Australia, it flowers from August to January.[15]
In Buenos Aires, Argentina, B. brevis begins flowering chasmogamously before flowering cleistogamously. It flowers chasmogamously from September to October, and cleistogamously from October to early January.[22]
Being a xeric grass, B. brevis is an important forage and fodder grass in arid and semi-arid regions of Argentina.[29]
B. brevis was known as lanku kachu to the Ranquel indigenous people, who ate it raw, or used it to make a flour for thickening meat broth or to make into bread.[4]
A segregate subspecies - B. brevis subsp. festucaroides was described in 1981, based on different forms of compression in anthers and caryopses. However, there is a whole range of forms between it and the type subspecies, so it is typically not recognised as distinct.[3]
B. brevis has at times been considered a variety or subspecies of B. catharticus. First in 1896, Carlo Luigi Spegazzini described Bromus unioloides var. rupestris, but noted that it has a very different appearance from Bromus unioloides (now called B. catharticus).[2] Then, in 1904, Eduard Hackel described Bromus unioloides var. brevis.[30]
Evidence for
These earlier positions were largely ignored until 1991, when Dr. Ana María Planchuelo attempted to define species boundaries within the Bromus catharticus complex of section Ceratochloa. She collected 16 morphological characteristics from 91 herbarium specimens of B. catharticus, B. brevis, B. bonariensis, and various varieties thereof, and analysed them phenetically. Based on the chosen characters, she found little differentiation between B. brevis and B. catharticus.[23] In 1998, based on this paper. she reinstated Bromus unioloides var. rupestris under the updated name Bromus catharticus var. rupestris.[17]
Evidence against
Evidence supporting the differentiation of the two species was published in a 1992 study (and a preceding doctoral thesis) by Dr. Carlos Naranjo. In these studies, he demonstrated using crossing experiments, phenetics, and chemotaxonomy that B. brevis and B. catharticus are distinct.[22][21]
Despite some records in the wild, he found that hybrids were difficult to produce between B. brevis and B. catharticus, and had low fertility when successful. From four hybrids produced between the two species, only 2.8% of flowers produced mature seeds, and only one fertile seed was obtained, indicating extremely low fertility. Additionally, the pollen fertility rate was 7.9%. This was possibly due to structural differences in chromosomes or genetic sterility. Additionally, hybridism is unlikely to occur in the natural environment due to pre-fertilisation barriers:
Most flowers in both species are cleistogamous (self-pollinating), and;
Chasmogamous flowers were found to be temporally isolated between species.[22][21]
Phenetic analysis, including 18 continuous and discrete characters, found that B. brevis was distinct from B. catharticus, but similar to B. parodiiand B. bonariensis, a result shared by crossing and chemotaxonomic results.[21]
A separate paper from 2015 sequenced the ndhF gene for 67 accessions of B. catharticus from throughout the Pampean Region, using B. brevis as a control. The result showed B. brevis as clearly a sister group to the B. catharticus accessions. However, the tree was not nested.[31]
Etymology
Bromus - from the Greek bromos (oat), out of broma (food).[32]
brevis - Latin for short, referring to the short culms.[15]
Gallery
B. brevis compact inflorescenceSward of B. brevisAn unusually large-panicled B. brevisA B. brevis spikelet
12Planchuelo, A.M. (1991). "ESTUDIOS SOBRE EL COMPLEJO BROMUS CATHARTICUS (POACEAE) I. EVALUACION ESTADISTICA DE LOS CARACTERES TAXONOMICOS". Kurtziana. 21: 243–257.
↑"Equipo Humano". Flora Argentina (in Spanish). Retrieved 2025-11-22.
12Museo Nacional de Buenos Aires.; Aires, Museo Nacional de Buenos (1905). Anales del Museo Nacional de Buenos Aires. Vol.ser.3:t.4 (1905). Buenos Aires: Impr. de Juan A. Alsina.
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