Relationship of the percentage of changes by species (%chSp) of orthologs with synonymous (dS) and nonsynonymous (dN) substitution rates. A, relationship of dN with the %chSp. B, relationship of dS with the %chSp. dN and dS values were obtained with PAML . Dot colors: orange, R. etli; red, A. tumefaciens; blue, S. meliloti; green, B. melitensis; and yellow, M. loti.