Molecular phylogeny in mytilids supports the wooden steps to deep-sea vents hypothesis.

Molecular data were used to study the diversity of mytilids associated with sunken-woods sampled in the Solomon Islands and discuss the 'wooden steps to deep-sea vent' hypothesis proposed by Distel et al. First, COI data used in a barcoding approach confirm the presence of four distinct species. Analyses of the 18S rDNA and COI dataset then confirmed that these sunken-wood mytilids belonged to a monophyletic group including all species from deep-sea reducing environments. Finally, we analyzed the relationships within this monophyletic group that include the Bathymodiolinae using a COI dataset and a combined analysis of mitochondrial COI and ND4 genes and nuclear rDNA 18S and 28S. Our study supported the 'wooden steps to deep-sea vent' hypothesis: one of the sunken-wood species had a basal position within the Bathymodiolionae, and all described vent and seep mussels included in our analyses were derived taxa within Bathymodiolinae.