title: Predatory functional response and prey choice identify predation differences between native/invasive and parasitised/unparasitised crayfish.
abstract: BACKGROUND
  Invasive predators may change the structure of invaded communities through predation and competition with native species. In Europe, the invasive signal crayfish Pacifastacus leniusculus is excluding the native white clawed crayfish Austropotamobius pallipes.
  
  
  RESULTS
  This study compared the predatory functional responses and prey choice of native and invasive crayfish and measured impacts of parasitism on the predatory strength of the native species. Invasive crayfish showed a higher (>10%) prey (Gammarus pulex) intake rate than (size matched) natives, reflecting a shorter (16%) prey handling time. The native crayfish also showed greater selection for crustacean prey over molluscs and bloodworm, whereas the invasive species was a more generalist predator. A. pallipes parasitised by the microsporidian parasite Thelohania contejeani showed a 30% reduction in prey intake. We suggest that this results from parasite-induced muscle damage, and this is supported by a reduced (38%) attack rate and increased (30%) prey handling time.
  
  
  CONCLUSIONS
  Our results indicate that the per capita (i.e., functional response) difference between the species may contribute to success of the invader and extinction of the native species, as well as decreased biodiversity and biomass in invaded rivers. In addition, the reduced predatory strength of parasitized natives may impair their competitive abilities, facilitating exclusion by the invader.
authors.affiliation: School of Environment, Natural Resources and Geography, College of Natural Sciences, Bangor University, Bangor, United Kingdom.
authors.forename: Neal R
authors.initials: NR
authors.lastname: Haddaway
authors.forename: Ruth H
authors.initials: RH
authors.lastname: Wilcox
authors.forename: Rachael E A
authors.initials: RE
authors.lastname: Heptonstall
authors.forename: Hannah M
authors.initials: HM
authors.lastname: Griffiths
authors.forename: Robert J G
authors.initials: RJ
authors.lastname: Mortimer
authors.forename: Martin
authors.initials: M
authors.lastname: Christmas
authors.forename: Alison M
authors.initials: AM
authors.lastname: Dunn
mesh_terms: D000818:Animals; D003400:Astacoidea / Q000502:physiology*; D044822:Biodiversity; D058865:Introduced Species; D010271:Parasites; D011157:Population Dynamics; D011235:Predatory Behavior