This dissertation documents an analysis of genetic diversity in the Botrychium lunaria complex using starch gel enzyme electrophoresis and statistical analysis of genetic relationships. The study resulted in identifying the genetic variation within and between the entities comprising the complex and revealed their geographic distribution. These results provided a basis for inferring what entities comprise the complex and how the entities may be recognized taxonomically. This study also examines the biogeography of the B. lunaria complex. I used the results of enzyme electrophoresis studies, statistical analysis and Geographical Information Systems (GIS) mapping to investigate the complex's origins, the relationships between its entities, how the entities arose and their patterns of geographic distribution. Studies revealed considerable genetic diversity within the B. lunaria complex as well as distinct geographic patterns to the complex's genetic diversity. In addition, I determined how the genetic entities should be recognized taxonomically and at which taxonomic levels they should be recognized. Geographic distribution of the members of the B. lunaria complex reflects their phylogenetic relationships. Their genetic composition, migration patterns and divergence times reveal genetic isolation that can probably be attributed to Quaternary glacial-interglacial cycles. The present distribution of members of the B. lunaria complex can also be explained, in part, by long distance dispersal via spores. Divergences between taxa occurred during different glacial periods. Distributions of taxa also indicate post-glacial spread of taxa and genotypes. Beringia, the landmass connecting eastern Siberia and Alaska, is a center of moonwort diversity as well as providing a colonization route between Eurasia and North America.