Maximum Likelihood tree showing phylogenetic relationships of MCR and hydrothermal vent vestimentiferan symbionts based (a) 16S rRNA and (b) ITS sequences using the K2+G+I and K2+G models, respectively. MCR Escarpia and Lamelliabrachia sp.2 symbiont sequences are highlighted in bold; numbers following names refer to specimen number while numbers in parenthesis, following clone representative sequence, indicate number of clones analyzed per specimen. An asterisk indicates that although Escarpia 689 was chosen as the representative sequence for haplotype 1, the latter was shared by Escarpia 199 (× 22), 689 (× 19); Lamellibrachia 387 (× 20), 389 (× 21) individuals. For 16S, ca. 1360 bp nucleotides were analyzed with sequences < 700 bp were excluded. The tree was rooted with methanotrophic Bathymodiolus mussel symbiont as an outgroup. ITS analysis included ca.575 nucleotides. The tree was rooted with the symbiont from Lucina floridana, a marine bivalve (clam) as an outgroup. Accession numbers follow host names and numbers at nodes (listed above 85) indicate the proportion of occurrences in 100 bootstrap replicates. Seep groups 1, 2 and, 3 and Vent group correspond to vestimentiferans symbionts highlighted in Thiel et al.