title: Two species of feminizing microsporidian parasite coexist in populations of Gammarus duebeni.
abstract: The amphipod crustacean Gammarus duebeni hosts two species of vertically transmitted microsporidian parasites, Nosema granulosis and Microsporidium sp. A. Here it is demonstrated that these co-occurring parasite species both cause infected females to produce female-biased broods. A survey of European G. duebeni populations demonstrates that these two parasites co-occur in six of 10 populations. These findings contrast with the theoretical prediction that two vertically transmitted feminizing parasites should not coexist in a panmictic population of susceptible hosts at equilibrium. Possible explanations for the co-occurrence of the two feminizing microsporidia in G. duebeni include the recent invasion of a new parasite, horizontal transmission of one or both parasites and the spread of alleles for resistance to the dominant parasite in host populations.
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham, UK. j.ironside@bham.ac.uk
authors.forename: J E
authors.initials: JE
authors.lastname: Ironside
authors.forename: J E
authors.initials: JE
authors.lastname: Smith
authors.forename: M J
authors.initials: MJ
authors.lastname: Hatcher
authors.forename: R G
authors.initials: RG
authors.lastname: Sharpe
authors.forename: D
authors.initials: D
authors.lastname: Rollinson
authors.forename: A M
authors.initials: AM
authors.lastname: Dunn
mesh_terms: D033304:Amphipoda / Q000469:parasitology*; D000818:Animals; D006790:Host-Parasite Interactions / Q000502:physiology; D016816:Microsporida / Q000502:physiology*; D016881:Microsporidiosis / Q000503:physiopathology* / Q000635:transmission*; D008954:Models, Biological; D011157:Population Dynamics; D012606:Scotland; D012744:Sex Ratio