| Whether a species will flourish or face extinction under a new climate regime is largely determined by its dispersal ability, its adaptive capacity or some combination of these processes. These processes have also played important roles in the evolutionary histories of species, ultimately shaping their contemporary distributions. In terrestrial studies, a landscape genetics approach is often used to explain how geographic, ecological and evolutionary processes interact to structure spatial genetic variation across populations, but these approaches have only begun to be used in marine ecosystems. This dissertation fills an emerging niche in marine ecology by taking an interdisciplinary seascape genetics approach to investigating the interplay of climate, dispersal and adaptation as shallow-water marine fishes respond to environmental heterogeneity over space and climatological shifts over time.;I begin by developing MARSPEC, a publicly available GIS database containing 18 high-resolution climate layers for the world ocean derived from satellite and in situ measures of sea surface temperature, salinity and bathymetry. I validate the use of these climate surfaces in questions related to marine spatial ecology by successfully predicting the invasion potential of the red lionfish, Pterois volitans, in the western North Atlantic and Caribbean Sea. Furthermore, I demonstrate that oceanographic dispersal barriers and salinity will limit the invasive spread of this fish in the face of future climate change.;Next I use microsatellite DNA analysis and spatial statistics to investigate the relative roles of environmental heterogeneity, gene flow, and historical processes in shaping the spatial scale of local adaptation in an estuarine fish, the Atlantic Silverside (Menidia menidia). I found that neutral processes, such as isolation by distance and secondary contact, could explain phenotypic dines as easily as selective ones, and that populations are genetically differentiated along a salinity gradient.;Finally, I test the hypothesis that strong genetic structure and species boundaries are maintained by environmental preferences rather than dispersal limitations in three Indo-West Pacific clownfish. Using paleo-niche models and mitochondrial DNA analysis, I determined that ecological divergence in Pleistocene refugia was an important diversifying force at multiple taxonomic levels within a marine biodiversity hotspot. |
