title: Interactive effects of genotype and food quality on consumer growth rate and elemental content.
abstract: Consumer body stoichiometry is a key trait that links organismal physiology to population and ecosystem-level dynamics. However, as elemental composition has traditionally been considered to be constrained within a species, the ecological and evolutionary factors shaping consumer elemental composition have not been clearly resolved. To this end, we examined the causes and extent of variation in the body phosphorus (P) content and the expression of P-linked traits, mass specific growth rate (MSGR), and P use efficiency (PUE) of the keystone aquatic consumer Daphnia using lake surveys and common garden experiments. While daphnid body %P was relatively constrained in field assemblages sampled across an environmental P gradient, unique genotypes isolated from these lakes showed highly variable phenotypic responses when raised across dietary P gradients in the laboratory. Specifically, we observed substantial inter- and intra-specific variation and differences in daphnid responses within and among our study lakes. While variation in Daphnia body %P was mostly due to plastic phenotypic changes, we documented considerable genetic differences in daphnid MSGR and PUE, and relationships between MSGR and body P content were highly variable among genotypes. Overall, our study found that consumer responses to food quality may differ considerably among genotypes and that relationships between organismal life-history traits and body stoichiometry may be strongly influenced by genetic and environmental variation in natural assemblages.
authors.affiliation: Environmental and Life Science Graduate Program, Trent University, Peterborough, Ontario, K9J 7B8, Canada.
authors.forename: Clay
authors.initials: C
authors.lastname: Prater
authors.affiliation: Environmental and Life Science Graduate Program, Trent University, Peterborough, Ontario, K9J 7B8, Canada.
authors.forename: Nicole D
authors.initials: ND
authors.lastname: Wagner
authors.affiliation: Department of Biology, Trent University, Peterborough, Ontario, K9L 1Z8, Canada.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Frost
mesh_terms: D000818:Animals; D003621:Daphnia / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D063427:Food Quality; D005838:Genotype; D060106:Lakes; D010758:Phosphorus / Q000378:metabolism
chemical_list: D010758:Phosphorus
keywords: 
  Daphnia
  ; G × E interaction; ecological stoichiometry; life-history evolution; phenotypic plasticity; phosphorus use efficiency; reaction norm