title: Terrestrial support of aquatic food webs depends on light inputs: a geographically-replicated test using tank bromeliads.
abstract: Food webs of freshwater ecosystems can be subsidized by allochthonous resources. However, it is still unknown which environmental factors regulate the relative consumption of allochthonous resources in relation to autochthonous resources. Here, we evaluated the importance of allochthonous resources (litterfall) for the aquatic food webs in Neotropical tank bromeliads, a naturally replicated aquatic microcosm. Aquatic invertebrates were sampled in more than 100 bromeliads within either open or shaded habitats and within five geographically distinct sites located in four different countries. Using stable isotope analyses, we determined that allochthonous sources comprised 74% (±17%) of the food resources of aquatic invertebrates. However, the allochthonous contribution to aquatic invertebrates strongly decreased from shaded to open habitats, as light incidence increased in the tanks. The density of detritus in the tanks had no impact on the importance of allochthonous sources to aquatic invertebrates. This overall pattern held for all invertebrates, irrespective of the taxonomic or functional group to which they belonged. We concluded that, over a broad geographic range, aquatic food webs of tank bromeliads are mostly allochthonous-based, but the relative importance of allochthonous subsidies decreases when light incidence favors autochthonous primary production. These results suggest that, for other freshwater systems, some of the between-study variation in the importance of allochthonous subsidies may similarly be driven by the relative availability of autochthonous resources.
authors.affiliation: Departamento de Ecologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro (UFRJ), Ilha do Fundão, PO Box 68020, Rio de Janeiro - RJ, Brazil.
authors.forename: Vinicius F
authors.initials: VF
authors.lastname: Farjalla
authors.affiliation: Department of Zoology & Biodiversity Research Centre, University of British Columbia, 6270 University Blvd., Vancouver, British Columbia, V6T 1Z4, Canada.|Biology Department and Center for Computational and Integrative Biology, Rutgers, The State University of NJ, Camden, New Jersey, 08103, USA.
authors.forename: Angélica L
authors.initials: AL
authors.lastname: González
authors.affiliation: Ecolab (UMR-CNRS 5245), Université de Toulouse, 118 route de Narbonne, 31062, Toulouse, France.
authors.forename: Régis
authors.initials: R
authors.lastname: Céréghino
authors.affiliation: CNRS, Ecologie des Forêts de Guyane (UMR-CNRS 8172), Campus Agronomique, F-97379, Kourou Cedex, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Dézerald
authors.affiliation: Departamento de Ecologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro (UFRJ), Ilha do Fundão, PO Box 68020, Rio de Janeiro - RJ, Brazil.
authors.forename: Nicholas A C
authors.initials: NA
authors.lastname: Marino
authors.affiliation: Graduate Program in Animal Biology, IBILCE, State University of São Paulo (UNESP), São José do Rio Preto-SP, Brazil.
authors.forename: Gustavo C O
authors.initials: GC
authors.lastname: Piccoli
authors.affiliation: 165 Braid Road, Edinburgh, EH10 6JE, UK.|Luquillo LTER, Institute for Tropical Ecosystem Studies, College of Natural Sciences, University of Puerto Rico at Rio Piedras, P.O. Box 70377, San Juan, Puerto Rico, 00936-8377, USA.
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Richardson
authors.affiliation: 165 Braid Road, Edinburgh, EH10 6JE, UK.|Luquillo LTER, Institute for Tropical Ecosystem Studies, College of Natural Sciences, University of Puerto Rico at Rio Piedras, P.O. Box 70377, San Juan, Puerto Rico, 00936-8377, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Richardson
authors.affiliation: Department of Animal Biology, Institute of Biology, University of Campinas (UNICAMP), PO Box 6109, Campinas-SP, CEP 13083-970, Brazil.
authors.forename: Gustavo Q
authors.initials: GQ
authors.lastname: Romero
authors.affiliation: Department of Zoology & Biodiversity Research Centre, University of British Columbia, 6270 University Blvd., Vancouver, British Columbia, V6T 1Z4, Canada.
authors.forename: Diane S
authors.initials: DS
authors.lastname: Srivastava
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000502:physiology*; D031231:Bromelia; D017753:Ecosystem; D020387:Food Chain; D005618:Fresh Water; D007448:Invertebrates / Q000502:physiology*
keywords: allochthonous carbon; allochthony; aquatic food webs; autochthonous carbon; autochthony; natural microcosms; stable isotopic analysis; tank bromeliads; tropics