Fig. 1. The evolution of genome size in the grasses inferred using the squared-change parsimony (SP) criterion. Ancestral genome sizes (in pg DNA per 2C nucleus) were reconstructed as continuous-valued characters on a cladogram of diploid grass species using SP with the rooted option. The phylogeny of the grasses was rooted using phylogenetic information derived from RNA structure. Closed and open circles indicate nodes with more than twofold increases or decreases in genome size, respectively. The node defining Bromeae leads to Bromus species and the node defining Triticeae leads to Triticum and Aegilops species.