Parthenogenesis

The advantage of sexual and parthenogenetic reproduction has long interested biologists and remains a central issue in Evolutionary Theory. Among insects a number of parthenogenetic forms are known, with a great diversity of mechanisms and distinctive features printed in their life history. This chapter does not intend to be a taxonomic revision of this reproductive mode, since a recent comprehensive documentation of reproductive transitions in insects in two parts is available (written by scholars Alisa Vershinina, Vladimir E. Gokhman and Valentina Kuznetsova), as well as recent reviews about constraints and genomic signatures printed by this reproductive mode, for example. Rather, in this manuscript we find all these aspects together, with many examples of insects and an update of old theories and new ideas that study of insect parthenogenesis has allowed to propose. We begin with a brief history of discovery of parthenogenesis, in which insects played a prominent role. Then, we review mechanisms that allow to get new life without fertilization, modes by which transitions between sexual and parthenogenesis occurs, constraints that may limit expansion of this reproductive mode in several taxa, as well as genomic and ecological footprints of this curious reproductive mode. A great diversity is found in insects in every aspect of parthenogenesis that we address this chapter. The advantage of sexual and parthenogenetic reproduction has long interested biologists and remains a central issue in Evolutionary Theory. This chapter begins with a brief history of discovery of parthenogenesis, in which insects played a prominent role. It reviews mechanisms that allow to get new life without fertilization, modes by which transitions between sexual and parthenogenesis occurs, constraints that may limit expansion of this reproductive mode in several taxa, as well as genomic and ecological footprints of this curious reproductive mode. The chapter addresses a great diversity which is found in insects in every aspect of parthenogenesis. Parthenogenesis is better regarded as an incomplete form of sexual reproduction. Restoration of diploidy post-meiosis is slightly more complicated requiring fusion of haploid nuclei from same gametic sex or ploidy restoration. Interspecific hybridization can disrupt meiosis and development and create opportunities for selection of cytological and developmental processes that rescue egg production and division.