Submitted to: International Journal of Plant Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/26/2003
Publication Date: 2/24/2004
Citation: Massa, A.N., K.B. Jensen, S.R. Larson, and D.J. Hole. 2004. Morphological Variation in Bromus section Ceratochloa germplasm of Patagonia. Can. J. of Bot. 82: 136-144. Interpretive Summary: Taxonomic treatments of taxa within South American Bromus species is controversial and disagreements exist regarding the number of species and morphological criteria that delimit taxa. This study explored the extent of morphological variation among six species of Bromus sect. Certaochloa distributed throughout the Patagonian region of Argentina and Chile. Results indicate that hexaploid germplasm of Bromus sect. Ceratochloa from Patagonia represent a single variable species, and that morphological variants within hexaploids are valid at the infraspecific level. Based on our data, two species are recognized within Bromus sect. Ceratochloa germplasm of Patagonia. These are B. catharticus Vahl and B. coloratus Steud. Bromus catharticus includes the hexaploid germplasm, and B. coloratus the octoploids.
Technical Abstract: South American representative of Bromus sect. Ceratochloa make up a morphologically diverse group of grasses localized to the southern Andes of Argentina and Chile. This study describes patterns of morphological variation among 30 accessions representing six species, correlates morphological and molecular data, and proposes a taxonomic realignment within sect. Ceratochloa of South America. Plant materials included 28 hexaploid (2n=6x=42) accessions and two octoploid (2n=8x=56) accessions representing B. catharticus Vahl, B. coloratus Steud., B. lithobius Trin., B. mango Desv., B. stamineus Desv. and B. tunicatus Phil. Based on multivariate analysis of 26 characters, morphological patterns were not congruent with previous taxonomic classifications. Two groups of hexaploid accessions were recognized. Group one consisted of B. coloratus, B. lithobius, and B. stamineus and group two consisted of B. catharticus, B. mango, and B. tunicatus. The Mantel test statistic showed a high correlation (r = 0.70, P< 0.001) between distances based on morphology and genetic similarities based on the proportion of shared DNA fragments. Overall, results indicated that hexaploids represent a single variable species (B. catharticus subsp. catharticus and subsp. stamineus) may exist within the hexaploids. Bromus coloratus is reserved for the octoploid accessions.