title: Warm vegetarians? Heat waves and diet shifts in tadpoles.
abstract: Temperature can play an important role in determining the feeding preferences of ectotherms. In light of the warmer temperatures arising with the current climatic changes, omnivorous ectotherms may perform diet shifts toward higher herbivory to optimize energetic intake. Such diet shifts may also occur during heat waves, which are projected to become more frequent, intense, and longer lasting in the future. Here, we investigated how heat waves of different duration affect feeding preferences in omnivorous anuran tadpoles and how these choices affect larval life history. In laboratory experiments, we fed tadpoles of three species on animal, plant, or mixed diet and exposed them to short heat waves (similar to the heat waves these species experience currently) or long heat waves (predicted to increase under climate change). We estimated the dietary choices of tadpoles fed on the mixed diet using stable isotopes and recorded tadpole survival and growth, larval period, and mass at metamorphosis. Tadpole feeding preferences were associated with their thermal background, with herbivory increasing with breeding temperature in nature. Patterns in survival, growth, and development generally support decreased efficiency of carnivorous diets and increased efficiency or higher relative quality of herbivorous diets at higher temperatures. All three species increased herbivory in at least one of the heat wave treatments, but the responses varied among species. Diet shifts toward higher herbivory were maladaptive in one species, but beneficial in the other two. Higher herbivory in omnivorous ectotherms under warmer temperatures may impact species differently and further contribute to changes in the structure and function of freshwater environments.
authors.affiliation: cE3c Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências da Universidade de Lisboa, Bloco C2, Campo Grande, 1749-016, Lisboa, Portugal.|Animal Ecology/Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, S-75236, Uppsala, Sweden.
authors.forename: B M
authors.initials: BM
authors.lastname: Carreira
authors.affiliation: Centro de Estudos Florestais, Instituto Superior de Agronomia da Universidade de Lisboa, 1349-017, Lisboa, Portugal.
authors.forename: P
authors.initials: P
authors.lastname: Segurado
authors.affiliation: Animal Ecology/Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, S-75236, Uppsala, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Orizaola
authors.affiliation: cE3c Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências da Universidade de Lisboa, Bloco C2, Campo Grande, 1749-016, Lisboa, Portugal.
authors.forename: N
authors.initials: N
authors.lastname: Gonçalves
authors.affiliation: cE3c Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências da Universidade de Lisboa, Bloco C2, Campo Grande, 1749-016, Lisboa, Portugal.
authors.forename: V
authors.initials: V
authors.lastname: Pinto
authors.affiliation: Animal Ecology/Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, S-75236, Uppsala, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Laurila
authors.affiliation: cE3c Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências da Universidade de Lisboa, Bloco C2, Campo Grande, 1749-016, Lisboa, Portugal.
authors.forename: R
authors.initials: R
authors.lastname: Rebelo
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001001:Anura / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D060434:Herbivory / Q000502:physiology*; D006358:Hot Temperature; D007814:Larva / Q000502:physiology
keywords: 
  Discoglossus galganoi
  ; 
  Hyla arborea
  ; 
  Hyla meridionalis
  ; Amphibian; carnivory; climate change; diet regulation; herbivory; omnivory; stable isotope mixing models