Evolutionary history of contagious asexuality in Daphnia pulex

Susanne Paland, John K. Colbourne, Michael Lynch

Research output: Contribution to journalArticlepeer-review

105 Scopus citations


Asexual taxa are short-lived, suggesting that transitions to asexuality represent evolutionary dead-ends. However, with high rates of clonal origin and coexistence of asexuals and sexuals via selective asymmetries, asexuality may persist in the long term as a result of a dynamic equilibrium between clonal origin and extinction. Few such systems have been studied in detail. Here, we investigate the evolutionary history of asexual lineages of Daphnia pulex, which are derived from sexual relatives via the inheritance of a dominant female-limited meiosis-suppressing locus and inhabit ponds throughout northeastern North America (NA). Our extensive sampling and subsequent phylogenetic analysis using mitochondrial sequence data reveals a young and genetically diverse asexual assemblage, reflecting high rates of clonal origin due to the contagious nature of asexuality. Yet, asexuality is restricted to two phylogroups (B and C) with historical and/or present associations with northeastern NA and is absent from a northwestern phylogroup (A), supporting a recent northeastern origin of asexuality in this species. Furthermore, macrogeographic patterns of genetic variability indicate that phylogroups B and C recolonized northeastern NA from opposite directions, yet their presently overlapping geographic distributions are similarly divided into an eastern asexual and a western sexual region. We attribute these patterns to a recent contagious spread of asexuality from a northeastern source. If environment-mediated selective asymmetries play no significant role in determining the outcome of competitive interactions between sexuals and asexuals, regions of contact may be setting the stage for continued asexual conquests.

Original languageEnglish (US)
Pages (from-to)800-813
Number of pages14
Issue number4
StatePublished - Apr 2005
Externally publishedYes


  • Evolution of sex
  • Geographical parthenogenesis
  • Mismatch analysis
  • Mitochondrial DNA
  • Phylogeography
  • Sex-limited meiosis suppressor

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • Agricultural and Biological Sciences(all)


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