Figure 6
From: The origin and evolution of geminivirus-related DNA sequences in Nicotiana
A model for double integration of GRD that is consistent with both the distribution of GRD in extant species of Nicotiana and the signature of purifying selection in the ancestors of modern GRD sequences. Parameter ω is the ratio of nonsynonymous to synonymous substitution rates, and is a precise measure of election pressure. Values of ω<1 indicate purifying selection, whereas ω=1 indicates neutral evolution.
