Parthenogenesis

by

Tanja Schwander

• LAST REVIEWED: 13 January 2014
• LAST MODIFIED: 13 January 2014
• DOI: 10.1093/obo/9780199941728-0011

Introduction

Parthenogenesis is the development of an unfertilized egg into a new individual. Coined by Carl Theodor Ernst von Siebold (b. 1804–d. 1885) in 1871, the literal meaning of parthenogenesis is “virgin reproduction”—reproduction in the absence of males. Historically, parthenogenesis has been used to refer to various forms of virgin reproduction by females, including cases of haplodiploid sex determination systems under which haploid, unfertilized eggs develop into males and females develop from fertilized (diploid) eggs. Currently, parthenogenesis in animals mostly refers to the production of daughters without genetic contributions from males (“female-producing parthenogenesis,” or thelytoky). It includes the rare examples of sperm-dependent parthenogenesis that require copulation, moving away from the original etymology. Among animals, female-producing parthenogenesis is estimated to occur in approximately one in a thousand species, with the incidence varying largely among groups. Classic examples of the extremes are mammals and birds without any parthenogenetic species, and aphids and water fleas, in which parthenogenetic generations are part of every species’ live cycle. In plants, the term “parthenogenesis” refers to a very specific process, in which the embryo develops mitotically from the egg cell. Thus plant “apomixis” is more comparable to animal parthenogenesis, although many apomictic plants remain dependent on pollen for the differentiation of the endosperm (the nutritive tissue within seeds). There are also many parallels between parthenogenesis and selfing, yet self-fertilizing hermaphrodites are not parthenogens, as their reproduction requires the union of female and male gametes. Female-producing parthenogenesis (and apomixis in plants) is widely studied in questions relating to the maintenance of sexual reproduction. This mode of reproduction would avoid certain costs associated with sexual reproduction, including the breaking up of co-adapted gene complexes, the production of sons as well as costs involved in mate finding, and copulation in the species without sperm dependence. In this context, female-producing parthenogenesis is often used interchangeably with asexuality, although parthenogenesis does not necessarily generate clones. Many forms of parthenogenesis involve meiosis, whereby ploidy levels (reduced during meiosis) are maintained between generations using specific cell regulatory or developmental mechanisms that can act before, during, or after the meiotic divisions. These different types of parthenogenesis are likely to arise using different mechanisms from bisexual ancestors.

General Overviews

Many reviews on costs and benefits of sexual reproduction include discussions of parthenogenesis, including the seminal contribution in Maynard Smith 1978. Probably the most comprehensive list to date of species reproducing parthenogenetically, as well as a discussion of modes of parthenogenesis in animals, is presented in Bell 1982, a review on the evolution of sexual reproduction. Reviews focusing more specifically on parthenogenesis include Suomalainen, et al. 1987 and Hughes 1989; a review on parthenogenesis in vertebrates is presented in Avise 2008. The most recent overview, Schön, et al. 2009, assembles case studies of different parthenogenetic groups and notably integrated studies on both plants and animals. White 1973 provides detailed discussions of cellular processes underlying parthenogenesis, as well as interactions between polyploidy and parthenogenesis.

• Avise, J. C. 2008. Clonality: The genetics, ecology and evolution of sexual abstinence in vertebrate animals. Oxford: Oxford Univ. Press.

  This book presents an excellent and complete review of the ecology and evolution of parthenogenesis in vertebrates. It is suitable for all researchers with an interest in parthenogenesis.

• Bell, G. 1982. The masterpiece of nature: The evolution and genetics of sexuality. Berkeley: Univ. of California Press.

  Bell’s book is a reference source among researchers studying sexual and parthenogenetic reproduction, especially in an ecological context. This book is best for graduate students and professionals looking for detailed information on historical and classical hypotheses, and for those seeking a broad survey of reproductive modes in animals.

• Hughes, R. N. 1989. A functional biology of clonal animals. London and New York: Chapman and Hall.

  This book presents a general overview of parthenogenetic modes of reproduction in animals and good reviews of the ecology and life history of individual groups characterized by parthenogenesis.

• Maynard Smith, J. 1978. The evolution of sex. New York: Cambridge Univ. Press.

  Although a seminal piece for the evolution of sex rather than specifically for parthenogenesis, the book discusses possible origins of new parthenogenetic strains from sexual ancestors (see also Evolution of Parthenogenesis). An argumentation on how likely different types of parthenogenesis are to generate new parthenogenetic strains is presented in a genetic framework.

• Schön, I., K. Martens, and P. J. van Dijk, eds. 2009. Lost sex: The evolutionary biology of parthenogenesis. Dordrecht, The Netherlands: Springer.

  DOI: 10.1007/978-90-481-2770-2

  The most recent collection of chapters covering reviews of parthenogenesis in different animal taxa as well as apomixis in plants.

• Suomalainen, E., A. Saura, and J. Lokki. 1987. Cytology and evolution of parthenogenesis. Boca Raton, FL: CRC Press.

  This textbook focuses on cellular mechanisms underlying parthenogenesis; explaining how parthenogenetic eggs are produced in diploid and polyploid groups (see Polyploidy and Parthenogenesis Modes) and what the expected consequences are for the genetic variability of a lineage and its persistence. It is an important resource for researchers working in the field.

• White, M. J. D. 1973. Animal cytology and evolution. 3d ed. Cambridge, UK: Cambridge Univ. Press.

  This book describes cellular mechanisms of parthenogenesis in different groups, with a special reference to interactions with sex determination systems and ploidy. It also provides good explanations of mechanisms underlying cyclical parthenogenesis, including the systems with very complex life histories (see Cyclical Parthenogenesis).