title: Determinants of life-history traits in a fish ectoparasite: a hierarchical analysis.
abstract: OBJECTIVE
  Unravelling the determinants of parasite life-history traits in natural settings is complex. Here, we deciphered the relationships between biotic, abiotic factors and the variation in 4 life-history traits (body size, egg presence, egg number and egg size) in the fish ectoparasite Tracheliastes polycolpus. We then determined the factors affecting the strength of the trade-off between egg number and egg size.
  
  
  METHODS
  To do so, we used 4-level (parasite, microhabitat, host and environment) hierarchical models coupled to a field database.
  
  
  RESULTS
  Variation in life-history traits was mostly due to individual characteristics measured at the parasite level. At the microhabitat level (fins of fish hosts), parasite number was positively related to body size, egg presence and egg number. Higher parasite number on fins was positively associated with individual parasite fitness. At the host level, host body size was positively related to the individual fitness of the parasite; parasites were bigger and more fecund on bigger hosts. In contrast, factors measured at the environmental level had a weak influence on life-history traits. Finally, a site-dependent trade-off between egg number and egg size existed in this population.
  
  
  CONCLUSIONS
  Our study illustrates the importance of considering parasite life-history traits in a hierarchical framework to decipher complex links between biotic, abiotic factors and parasite life-history traits.
authors.affiliation: Laboratoire Evolution et Diversité Biologique, U.M.R 5174, C.N.R.S - Université Paul Sabatier, 118 route de Narbonne, F-31062 Toulouse cedex 4, France.
authors.forename: G
authors.initials: G
authors.lastname: Loot
authors.affiliation: ONEMA, Le Nadar Hall C 5 sq Félix Nadar 94300 Vincennes, France.
authors.forename: N
authors.initials: N
authors.lastname: Poulet
authors.affiliation: Laboratoire Evolution et Diversité Biologique, U.M.R 5174, C.N.R.S - Université Paul Sabatier, 118 route de Narbonne, F-31062 Toulouse cedex 4, France.
authors.forename: S
authors.initials: S
authors.lastname: Brosse
authors.affiliation: Laboratoire Evolution et Diversité Biologique, U.M.R 5174, C.N.R.S - Université Paul Sabatier, 118 route de Narbonne, F-31062 Toulouse cedex 4, France.
authors.forename: L
authors.initials: L
authors.lastname: Tudesque
authors.affiliation: IRD, MIVEGEC (UMR CNRS/IRD/UM1), 911 Av. Agropolis, BP 64501, FR-34394 Montpellier cedex 5, France.
authors.forename: F
authors.initials: F
authors.lastname: Thomas
authors.affiliation: Laboratoire Evolution et Diversité Biologique, U.M.R 5174, C.N.R.S - Université Paul Sabatier, 118 route de Narbonne, F-31062 Toulouse cedex 4, France.
authors.forename: S
authors.initials: S
authors.lastname: Blanchet
mesh_terms: D000818:Animals; D049628:Body Size / Q000502:physiology; D052284:Clutch Size / Q000502:physiology; D033342:Copepoda / Q000502:physiology*; D004478:Ectoparasitic Infestations / Q000469:parasitology / Q000662:veterinary*; D005260:Female; D005393:Fish Diseases / Q000469:parasitology*; D005399:Fishes / Q000469:parasitology*; D006790:Host-Parasite Interactions; D008018:Life Cycle Stages / Q000502:physiology*; D008297:Male; D015053:Zygote / Q000166:cytology