The primary objective of these studies is to ascertain mechanisms of organism dispersal and rates of gene flow between deep-sea hydrothermal vent fields associated with contiguious and non-contiguous oceanic ridge systems. A second, but equally important objective of these studies will be to delimit the genetic boundaries and systematic relationships among the suite of molluscan species occupying these unusual abyssal environments. As hydrothermal vents share significant numbers of confamilial, congeneric and perhaps conspecific molluscan taxa with certain cold-water sulfide/methane seeps, the later environments will also be investigated as additional sources of larval recruitment to the ridge hydrothermal systems. Drs. Lutz and Vjrienhoek will sample the molluscan fauna associated with a number of geographically-separated vent and seep sites in the eastern Pacific, the Gulf of Mexico and along the mid-Atlantic Ridge. They will use electrophoretic and molecular techniques to examine three discrete models ("island" "linear stepping-stone", and "reservoir") of population structure, colonization, and gene flow in deep-sea vent populations. Morphological features associated with juvenile molluscan shells will be analyzed to infer modes of larval development of species sampled from the various vent and seep habitats. Inferences drawn from such analyses should provide a basis for an approximate rank-ordering of vent/seep molluscan species according to dispersal capability. This, in turn, when coupled with genetic studies, should permit us a test of the validity of several recent hypotheses concerning the evolutionary consequences of different life-history strategies associated with the spectrum of organisms encountered at deep-sea vents and seeps.
