“…Reconstructing the evolution of C 4 photosynthesis is challenging as it requires the complex coordination of anatomical, ultrastructural, biochemical, and gene regulatory changes from C 3 ancestors ( Hibberd and Covshoff, 2010 ; Gowik and Westhoff, 2011 ; Sage et al , 2012 , 2014 ; Williams et al , 2012 ; Hancock and Edwards, 2014 ). In bringing together these aspects, a model of C 4 evolution where Kranz anatomy is formed around individual veins has been developed over the last 30 years, which includes potential evolutionary precursors and a number of transitional, evolutionary-stable states ( Monson et al , 1984 ; Edwards and Ku, 1987 ; Sage, 2004 ; Gowik and Westhoff, 2011 ; Sage et al , 2012 , 2014 ).…”