Figure 8.

d_N/d_S for all genes, all taxa (including Epifagus) vs.Panax. Most genes evolve more quickly in Ipomoea than in Nicotiana (tobacco), indicating relaxed constraint on plastid genes even before evolution of parasitism in Convolvulaceae. Constraint is further relaxed in Cuscuta exaltata and is most relaxed in Cuscuta obtusiflora, although photosynthetically related genes remain highly constrained. In general, genes present in Epifagus virginiana are under higher levels of constraint than in Cuscuta obtusiflora, despite the retention of photosynthetic genes in Cuscuta.