Bromus pictus of the B. setifolius complex (section Pnigma): numerical taxonomy and chromosome evidence for species rank

Abstract

Two biotic sympatric taxa of the Bromus setifolius complex, which are presently considered as varieties, were studied using cytological and numerical taxonomy methods. The numerical taxonomy analysis (cluster and principal components analysis) based on 35 characters showed the existence of two phenetically significant groups. One is formed by individuals that correspond to B. setifolius Presl. and the other by individuals with the characters of Bromus pictus Hook. All plants of B. setifolius had 2n = 4x = 28, and all the B. pictus individuals had 2n = 10x = 70. Other cytological differences between the two taxa were found, e.g., karyotype formulae, type of satellites, basic genome length, asymmetry, C-banding patterns, and meiotic chromosome behavior. Cytological differences, which parallel the constant morphological features exhibited by each taxa, justify specific status. Taking into acount other characters, such as perenniality, breeding system, and reproductive isolation barrier, the relationships and evolution of these taxa are discussed. Key words: Bromus setifolius, Bromus pictus, numerical taxonomy, karyotype, C-banding.