We are particularly interested in C4-like and incomplete or unoptimized C4 species. For example, Flaveria brownii (Acanthaceae) has a strong and functional C4 cycle but still retains Rubisco and C3 cycle activity in its mesophyll tissues, and also lacks certain characteristics of an optimized C4 phenotype, such as specific amino acid substitutions that modify the kinetics of key enzymes for C4 function.^22,23 Blepharis (Acanthaceae) also includes C4-like phenotypes, as well as an apparent species complex spanning C2 to C4 phenotypes.²⁴ C4 like and unoptimized C4 species are of interest because they may represent C4 evolution occurring in the present, before our eyes. Intraspecific variation in C4 cycle activity and integration may represent the evolutionary assembly of the C4 phenotype concurrent with speciation. In both cases, population genomics and modified GWAS approaches represent an unexplored route to new insight into late-stage C4 evolution. For this reason, we are taking a “deep dive” into Flaveria and Blepharis and sequencing as many species of both groups as possible, with a particular focus on population-level sequencing of both living and herbarium materials.