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Dissertation Defense:
Evolution and biogeography of
 hydrothermal vent organisms

Luis Hurtado
Monterey Bay Aquarium Research Institute

Friday, April 26, 2002
3:00 p.m.–Pacific Forum

Courtesy of Rich Lutz

To study several aspects of evolution and biogeography of hydrothermal vent creatures, I used molecular tools to examine genetic variation among individuals of several vent species. These species were collected at several localities throughout their distribution range in the East Pacific Ocean. For each species, I inferred levels gene flow and genetic differentiation among localities. The results shed light on the dispersal modes of these species and the factors that may restrict their dispersal. In some cases, the high degree of genetic differentiation suggested the possible existence of several species new to science. For all the species analyzed, I found that abrupt changes in genetic differentiation occur between particular localities. I propose several potential barriers that may affect dispersal of vent larvae in the East Pacific Ocean. Next, I used population genetic and phylogenetic analyses to study the mode of transmission of symbiotic bacteria in the vent clam Calyptogena magnifica. I found compelling evidence that the bacterial endosymbiont of this clam species is only transmitted vertically through the mother’s eggs. This suggests that the bacteria may have lost their ability to reinfect C. magnifica from the environment. This symbiosis may parallel the first stages in the acquisition of mitochondria and other organelles by eukaryotic cells. Finally, I used molecular clocks to test whether vent vestimentiferan tubeworms correspond to an ancient or recent evolutionary lineage.

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