Most marine organisms are very different from terrestrial organisms in that they disperse their numerous offspring into ocean currents as tiny larvae to find a suitable place to live. A major focus of marine biology today is to try to see into this "black box" of where and how larvae disperse, as this has significant consequences for understanding and conserving marine animals and plants. The goal of this study is to better understand the role of "stepping-stones" of habitat in connecting distant populations to each other through larval dispersal. This goal will be achieved through a comparison of the population genetics of marine snail species that are able to use waterless atolls as stepping-stones to those of their close freshwater relatives that cannot. It is hypothesized that populations of the marine species will be better connected to one another than populations of freshwater species even though both have marine larvae.
It has long been assumed that fisheries and populations of marine organisms were inexhaustible because they could always be replenished from elsewhere. The recent collapse of many fisheries, combined with recent studies of marine population genetics, have shown that this is not the case; larvae may often return to their birthplace, or only disperse for a short distance. If this is so, it will be important to set up marine reserves in networks so that they are close enough together to "catch" larvae that disperse from neighboring reserves in a manner that is similar to the function of terrestrial greenbelts or corridors. An understanding of how natural marine stepping-stones work will be important to this effort.
