Fig. 4.

Evolution of lodicules as indicated by B class gene expression. A schematic of the grass family phylogeny with the position of the outgroups examined in this study as described by the Grass Phylogeny Working Group. Lodicules evolve in the grasses after the divergence of the basal grass Streptochaeta. B class genes are consistently expressed in stamens and the organ whorl just outside the stamens. This whorl just outside the stamens is the inner tepals of Elegia and Joinvillea, the bracts X–XII of Streptochaeta, and the lodicules of the grasses. Both position and B class gene expression indicate lodicules are modifications of the inner tepals, with bracts X–XII of Streptochaeta being an intermediate step in this process. BEP clade, Bambusoideae, Erhartoideae, and Pooideae; PACCAD clade, Panicoideae, Arundinoideae, Centothecoideae, Chloridoideae, Aristidoideae, and Danthonioideae.