title: Patterns and mechanisms in instances of endosymbiont-induced parthenogenesis.
abstract: Female-producing parthenogenesis can be induced by endosymbionts that increase their transmission by manipulating host reproduction. Our literature survey indicates that such endosymbiont-induced parthenogenesis is known or suspected in 124 host species from seven different arthropod taxa, with Wolbachia as the most frequent endosymbiont (in 56-75% of host species). Most host species (81%, 100 out of 124) are characterized by haplo-diploid sex determination, but a strong ascertainment bias likely underestimates the frequency of endosymbiont-induced parthenogenesis in hosts with other sex determination systems. In at least one taxon, hymenopterans, endosymbionts are a significant driver of transitions from sexual to parthenogenetic reproduction, with one-third of lineages being parthenogenetic as a consequence of endosymbiont infection. Endosymbiont-induced parthenogenesis appears to facilitate the maintenance of reproductive polymorphism: at least 50% of species comprise both sexual (uninfected) and parthenogenetic (infected) strains. These strains feature distribution differences similar to the ones documented for lineages with genetically determined parthenogenesis, with endosymbiont-induced parthenogens occurring at higher latitudes than their sexual relatives. Finally, although gamete duplication is often considered as the main mechanism for endosymbiont-induced parthenogenesis, it underlies parthenogenesis in only half of the host species studied thus far. We point out caveats in the methods used to test for endosymbiont-induced parthenogenesis and suggest specific approaches that allow for firm conclusions about the involvement of endosymbionts in the origin of parthenogenesis.
authors.affiliation: Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
authors.forename: W-J
authors.identifier: 0000-0003-2585-6406
authors.initials: WJ
authors.lastname: Ma
authors.affiliation: Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
authors.forename: T
authors.initials: T
authors.lastname: Schwander
mesh_terms: D000818:Animals; D004171:Diploidy; D005260:Female; D006927:Hymenoptera; D010312:Parthenogenesis; D013559:Symbiosis; D020577:Wolbachia / Q000235:genetics / Q000502:physiology
keywords: 
  Wolbachia
  ; bacteria; endosymbionts; gamete duplication; haplo-diploid sex determination; infectious parthenogenesis; thelytoky