Introduction

This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book describes parthenogenesis, or "virgin birth", which is known from several groups and long before similar phenomena in plants and in animals. It also describes special types of asexual reproduction in higher algae, mosses, and ferns as apogamy and apospory. The book explains different types of apomixes. It discusses recent progress that has been made in studies of the genetic background of apomixis, although it still needs more information about its regulation and origin. The book also discusses the connections between apomixis and other traits like polyploidy, hybridization, self-incompatibility, and self-fertilization. It shows that other patterns in apomictic complexes than in sexual groups have to be assayed partly by other methods. Many biologists have been interested in geographical trends connected with the distribution of related sexual and apomictic taxa.