Population genetics and biogeography of vestimentiferan tube worms

Molecular markers were used to assess the geographical ranges and estimate rates of gene flow in several species of vestimentiferan tube worm from the eastern Pacific Ocean. Small specimens (<5 cm) of Tevnia jerichonana and Oasisia alvinae are difficult to distinguish morphologically; however, species-specific allozymes allowed unequivocal identification of specimens from sites along the East Pacific Rise (EPR). Both T. jerichonana and O. alvinae were found at 9°, 11° and 13°N latitude; only O. alvinae occurred at 21°N; and neither occurred along the Galapagos Rift. Estimated rates of gene flow were sufficient (i.e. Nm>1.0) to counteract significant genetic drift in each species, and dispersal appeared to occur in a predominantly stepping-stone fashion. In addition, DNA sequence information from a 637 bp region of the mitochondrial COI gene was used to examine genetic diversity and geographical continuity in new Ridgeia piscesae specimens from the northeastern Pacific. The range of this species is now known to include sites ranging between 41°N on the Gorda Ridge and 49°N on the Southern Explorer Ridge. Sequence divergence throughout this range did not exceed 0.8%, which is consistent with intraspecific levels of sequence variation in other vent and seep species. Finally, the global distribution of vestimentiferan tube worms is reviewed.