Frigid, dark, and energy-deprived, the deep sea was long considered hostile to life. However, new sampling technologies and intense international research efforts in recent decades have revealed a remarkably rich fauna and an astonishing variety of novel habitats. These recent discoveries have changed the way we look at global biodiversity. In "Deep-Sea Biodiversity," Michael Rex and Ron Etter present the first synthesis of patterns and causes of biodiversity in organisms that dwell in the vast sediment ecosystem that blankets the ocean floor. They provide the most comprehensive analysis to date of geographic variation in benthic animal abundance and biomass. The authors document geographic patterns of deep-sea species diversity and integrate potential ecological causes across scales of time and space. They also review the most recent molecular population genetic evidence to describe how and where evolutionary processes have generated the unique deep-sea fauna. "Deep-Sea Biodiversity" offers a new understanding of marine biodiversity that will be of general interest to ecologists and is crucial to responsible exploitation of natural resources at the deep-sea floor.