Examination of vestimentiferan worms attributed to the genus Ridgeia from more than 50 vent sites in the northeast Pacific indicates that only one species is present. We amalgamate Ridgeia piscesae Jones and R. phaeophiale Jones under the name R. piscesae and include other forms previously suspected to be different species. Allozyme evidence supports the hypothesis that the populations belong to a highly plastic phenotype. The distance data indicate no substantial genetic differences among populations along Juan de Fuca Ridge and across a transform fault to the northern Gorda Ridge. Morphological data indicate that the original distinction of two species on the basis of obturacular saucer number and tube colour was based on the extremes of a continuum of characteristics that relate to animal size, levels of predation, and probably vent fluid conditions. The intriguing effect of habitat on phenotype in this abundant vent animal requires further investigation now that the taxonomy is better understood.
Phenotypic Variation and Fitness in a Metapopulation of Tubeworms (Ridgeia piscesae Jones) at Hydrothermal Vents
