Variation in community structure within hydrothermal vent mussel beds of the East Pacific Rise

Patterns in invertebrate community structure associated with mussel beds at 3 hydrothermal vents on the northern East Pacific Rise (NEPR) were explored using quantitative, replicate sampling methods and were compared to those of southern East Pacific Rise (SEPR) mussel beds (similar to3000 km apart). Univariate measures of diversity (H', J') did not differ among 3 NEPR mussel beds. Diversity by most estimates was lower at NEPR mussel beds than at SEPR mussel beds. Invertebrate faunas of NEPR and SEPR mussel beds belong to the same biogeographic province, and the numerically dominant species at NEPR mussel beds were also numerical dominants at SEPR mussel beds. Pasterns of community structure within and among NEPR mussel beds, between NEPR and SEPR mussel beds, and between 'young' (<6 yr) and 'old' (>8 yr) mussel beds could be differentiated using multivariate techniques based on species-abundance matrices. Overall, these observations suggest that NEPR and SEPR mussel-bed communities are remarkably similar, differing primarily in the relative abundances of their shared, numerically dominant species and in the composition of the rare species.