Table 1. Relative-rate test for comparing the molecular evolutionary rates of 16S rRNA gene sequences between Curculioniphilus symbionts of Curculionini weevils, Sodalis-allied symbionts of Sitophilus grain weevils and their free-living relatives.

Lineage 1	Lineage 2	Outgroup	K1a	K2b	K1-K2	K1/K2	P-valuec
Curculioniphilus symbionts of Curculionini weevilsd	Escherichia coli (J01695)	Vibrio cholera (X74694)	0.126	0.106	0.020	2.18	0.0293*
Sodalis-allied symbionts of Sitophilus weevilse	Escherichia coli (J01695)	Vibrio cholera (X74694)	0.121	0.107	0.014	1.63	0.1029
Sodalis-allied symbionts of Curculionini weevilsf	Escherichia coli (J01695)	Vibrio cholera (X74694)	0.107	0.106	0.001	0.12	0.9061
Sodalis glossinidius (AP008232)	Escherichia coli (J01695)	Vibrio cholera (X74694)	0.107	0.106	0.001	0.14	0.8901
Curculioniphilus symbionts of Curculionini weevilsd	Sodalis-allied symbionts of Sitophilus weevilse	Escherichia coli (J01695)	0.098	0.078	0.020	2.83	0.0047*
Curculioniphilus symbionts of Curculionini weevilsd	Sodalis-allied symbionts of Curculionini weevilsf	Escherichia coli (J01695)	0.099	0.063	0.036	5.14	< 0.0001*
Curculioniphilus symbionts of Curculionini weevilsd	Sodalis glossinidius (AP008232)	Escherichia coli (J01695)	0.099	0.069	0.030	4.39	< 0.0001*
Sodalis-allied symbionts of Sitophilus weevilse	Sodalis-allied symbionts of Curculionini weevilsf	Escherichia coli (J01695)	0.078	0.064	0.015	4.88	< 0.0001*
Sodalis-allied symbionts of Sitophilus weevilse	Sodalis glossinidius (AP008232)	Escherichia coli (J01695)	0.078	0.069	0.009	2.23	0.0255*
Sodalis-allied symbionts of Curculionini weevilsf	Sodalis glossinidius (AP008232)	Escherichia coli (J01695)	0.063	0.069	–0.006	–1.60	0.1092

The maximum likelihood tree in figure 1 was used as a guide tree.

^aEstimated mean distance between lineage 1 and the last common ancestor of lineages 1 and 2.

^bEstimated mean distance between lineage 2 and the last common ancestor of lineages 1 and 2.

^cP-value was generated using the program RRTree (Robinson-Rechavi and Huchon, 2000). Asterisks indicate statistically significant differences.

^dCurculioniphilus symbionts of C. sikkimensis (AB573633), A. pictus (AB573610) and K. antennatus (AB573611).

^eSodalis-allied symbionts of S. oryzae (AF005235), S. zeamais (M85269) and S. granarius (AY126638).

^fSodalis-allied symbionts of C. sikkimensis (AB514505), A. roelofsi (AB604872) and C. hachijoensis (AB604873).