Figure 2.

Simple cladogram of major cereal speciation. Numbers are in Ma (millions of years ago). Orange sun: grass speciation event 75 Ma. Blue stars: polyploidy events; the major grass polyploidy event immediately after the grass speciation event occurred approximately 70 Ma. The Ehrhartoideae clade, which includes rice, arose approximately 55 Ma. The Pooideae clade, which includes wheat and barley, arose around 44 Ma; Chloridoideae, which contains foxtail millet 28 Ma, and the Panicoids, which include maize and sorghum, arose approximately 24 Ma. The branch length is not proportional to the number of substitutions per site. (Online version in colour.)