PATTERNS OF DISPERSAL AND LARVAL DEVELOPMENT OF ARCHAEOGASTROPOD LIMPETS AT HYDROTHERMAL VENTS IN THE EASTERN PACIFIC

Patterns of dispersal and larval development were examined in four spe cies of archaeogastropod limpets from hydrothermal vents along the nor thern East Pacific Rise and Galapagos Rift. Allozyme analysis revealed that recognized subspecies Lepetodrilus elevatus elevatus (McLean) an d L.e. galriftensis (McLean), occurred sympatrically along the East Pa cific Rise and should be treated as full species. Larval shell charact eristics of L. elevatus (s.s.) and L. galriftensis and two other sympa tric species, Lepetodrilus pustulosus (McLean) and Eulepetopsis vitrea (McLean), suggest that all four species possess nonplanktotrophic mod es of development which may limit long-distance dispersal capabilities . Theoretical considerations suggest that species with limited long-di stance dispersal will migrate among habitat islands in a 'stepping-sto ne' fashion, and thus, are expected to exhibit genetic evidence of 'is olation-by-distance'. Notwithstanding, E. vitrea and L. pustulosus did not exhibit the expected decline in rates of gene flow with increasin g geographic distances between localities, Apparently for these two sp ecies, modes and rates of dispersal could not be predicted from a know ledge of larval shell morphology. Although L. elevatus and L. galrifte nsis exhibited trends that may be consistent with 'isolation-by-distan ce', the number of population samples available for this study were in adequate to reject the null hypothesis of genetic structure being inde pendent of geographical distance. Copyright (C) 1997 Elsevier Science B.V.