This book aims at defining and reassessing the role of population genetics in conservation biology and seeks to identify the progress made in the field during the last decade. It deals with conservation genetics from several currently researched points of view, namely, ecological and demographic measures of rarity or population persistence, loss of genetic variation, inbreeding, reduced migration rates and increased selective pressures under stress and the role of social behaviour and metapopulation structure. The use of molecular variation as the basis of naming or selecting target taxa and some strategic decisions about genetic variance maximization in the conserved population or community units are analysed. Several case studies and scenarios illustrate the application of genetic information in conservation practices.