Population genetics has made great strides in applying statistical analysis and mathematical modeling to understand how genes mutate and spread through populations over time. But real populations also live in space. Streams, mountains, and other geographic features often divide populations, limit migration, or influence gene flow. This book examines the processes that determine geographic patterns of genetic variation, providing a comprehensive guide to their study and interpretation. It has a unique focus on the mathematical relationships of spatial statistical measures of patterns to stochastic processes.