Fidelity varies in the symbiosis between a gutless marine worm and its microbial consortium

Table 2 Levels of partner fidelity between O. algarvensis and its symbiotic consortia based on analyses in this study

	Observations					Indication
Symbiont	Significant effect on genetic distance		Mitochondria-symbiont co-divergence pattern^c	Relative abundance^d	Other	Fidelity
**Ca.Thiosymbion**	Mitochondria^a		Strong	41.6%	Detected in all host individuals. High genomic divergence between host maternal lineages A and B at both locations	Strict
Gamma3	Mitochondria^a	Location^b	Present	28.3%	Detected in all host individuals. A single switch from an A- to a B-host observed	Strong
Delta1a			Weak	5.3%	Detected in all A-hosts from both locations but in < 50% of B-hosts from both locations	Moderate
Delta1b		Location^b	Present	6.1%	Not detected in A-hosts from Sant’ Andrea but detected in 65–100% of other host individuals	Moderate
Delta3	NA^e	NA^e	NA^e	0.3%	Detected in only 0–15% of host individuals	NA^e
Delta4		Location^b	Weak	14.9%	Detected in 85–100% of host individuals	Weak
Spirochete			Absent	3.4%	Detected in all host individuals	Absent

^aPairwise genetic distances of symbionts were explained by their host mitochondrial lineages A or B (A- or B-hosts)
^bPairwise genetic distances of symbionts were explained by locations
^cRefer Supplementary Fig. S8 and Supplementary Table S6
^dMean relative read abundances across all host individuals
^eNot assessed due to the very low abundance of this symbiont in only six host individuals