title: Mutualistic ants contribute to tank-bromeliad nutrition.
abstract: OBJECTIVE
  Epiphytism imposes physiological constraints resulting from the lack of access to the nutrient sources available to ground-rooted plants. A conspicuous adaptation in response to that lack is the phytotelm (plant-held waters) of tank-bromeliad species that are often nutrient-rich. Associations with terrestrial invertebrates also result in higher plant nutrient acquisition. Assuming that tank-bromeliads rely on reservoir-assisted nutrition, it was hypothesized that the dual association with mutualistic ants and the phytotelm food web provides greater nutritional benefits to the plant compared with those bromeliads involved in only one of these two associations.
  
  
  METHODS
  Quantitative (water volume, amount of fine particulate organic matter, predator/prey ratio, algal density) and qualitative variables (ant-association and photosynthetic pathways) were compared for eight tank- and one tankless-bromeliad morphospecies from French Guiana. An analysis was also made of which of these variables affect nitrogen acquisition (leaf N and δ(15)N).
  
  
  RESULTS
  All variables were significantly different between tank-bromeliad species. Leaf N concentrations and leaf δ(15)N were both positively correlated with the presence of mutualistic ants. The amount of fine particulate organic matter and predator/prey ratio had a positive and negative effect on leaf δ(15)N, respectively. Water volume was positively correlated with leaf N concentration whereas algal density was negatively correlated. Finally, the photosynthetic pathway (C3 vs. CAM) was positively correlated with leaf N concentration with a slightly higher N concentration for C3-Tillandsioideae compared with CAM-Bromelioideae.
  
  
  CONCLUSIONS
  The study suggests that some of the differences in N nutrition between bromeliad species can be explained by the presence of mutualistic ants. From a nutritional standpoint, it is more advantageous for a bromeliad to use myrmecotrophy via its roots than to use carnivory via its tank. The results highlight a gap in our knowledge of the reciprocal interactions between bromeliads and the various trophic levels (from bacteria to large metazoan predators) that intervene in reservoir-assisted nutrition.
authors.affiliation: IRD, UMR AMAP (botAnique et bioinforMatique de l'Architecture des Plantes), Boulevard de la Lironde, TA A-51/PS2, F-34398 Montpellier Cedex 5, France. celine.leroy@ird.fr
authors.forename: Céline
authors.initials: C
authors.lastname: Leroy
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Carrias
authors.forename: Bruno
authors.initials: B
authors.lastname: Corbara
authors.forename: Laurent
authors.initials: L
authors.lastname: Pélozuelo
authors.forename: Olivier
authors.initials: O
authors.lastname: Dézerald
authors.forename: Olivier
authors.initials: O
authors.lastname: Brouard
authors.forename: Alain
authors.initials: A
authors.lastname: Dejean
authors.forename: Régis
authors.initials: R
authors.lastname: Céréghino
mesh_terms: D000818:Animals; D001000:Ants / Q000502:physiology*; D031229:Bromeliaceae / Q000502:physiology*; D005616:French Guiana; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000032:analysis; D010788:Photosynthesis; D013559:Symbiosis; D014867:Water / Q000378:metabolism*
chemical_list: D009587:Nitrogen Isotopes; D014867:Water; D009584:Nitrogen
keywords: Algae; Bromeliaceae; Formicinae; French Guiana; ants; food webs; mutualistic interactions; nitrogen; phytotelmata; stable isotopes; tank bromeliad; δ15N