Table 2.

Selection analyses results.

EGV1	EGV2	Connecting branch	P value for neg. selection	ω1	P1
BG1	BG2	FG	0	0.027	0.76
BG1	FG	BG2	0.021	0	0.32
FG	BG1	BG2	0.00029	0.18	0.80
FG	FG	BG1	0.00013	0	0.40

For each test, each clade was assigned to a foreground partition (FG) or one of two background partitions (BG1 and BG2). We report P values for significance tests for purifying selection along foreground lineages and the parameter point estimates for the foreground partition (w1 = dN/dS of negateively evolving codon sites and P1 = the proportion of all codon sites that are negatively evolving) under the alternative model (which allows purifying selection).