title: Biotic and abiotic factors investigated in two Drosophila species - evidence of both negative and positive effects of interactions on performance.
abstract: Multiple environmental factors acting in concert can interact and strongly influence population fitness and ecosystem composition. Studies investigating interactions usually involve only two environmental factors; most frequently a chemical and another abiotic factor such as a stressful temperature. Here we investigate the effects of three environmental factors: temperature, an insecticide (dimethoate) and interspecific co-occurrence. We expose two naturally co-occurring species of Drosophila (D. hydei and D. melanogaster) to the different environments during development and examine the consequences on several performance measures. Results are highly species and trait specific with evidence of two- and three-way interactions in approximately 30% of all cases, suggesting that additive effects of combined environmental factors are most common, and that interactions are not universal. To provide more informative descriptions of complex interactions we implemented re-conceptualised definitions of synergism and antagonism. We found approximately equal proportions of synergistic and antagonistic interactions in both species, however the effects of interactions on performance differed between the two. Furthermore, we found negative impacts on performance in only 60% of interactions, thus our study also reveals a high proportion of cases with positive effects of interactions.
authors.affiliation: Department of Chemistry and Bioscience, Section of Biology and Environmental Science, Aalborg University, Fredrik Bajers Vej 7H, DK-9220 Aalborg E, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Ørsted
authors.affiliation: Department of Bioscience, Section of Genetics, Ecology and Evolution, Aarhus University, Ny Munkegade 114, DK-8000 Aarhus C, Denmark.
authors.forename: Mads Fristrup
authors.initials: MF
authors.lastname: Schou
authors.affiliation: Department of Chemistry and Bioscience, Section of Biology and Environmental Science, Aalborg University, Fredrik Bajers Vej 7H, DK-9220 Aalborg E, Denmark.|Department of Bioscience, Section of Genetics, Ecology and Evolution, Aarhus University, Ny Munkegade 114, DK-8000 Aarhus C, Denmark.
authors.forename: Torsten Nygaard
authors.initials: TN
authors.lastname: Kristensen
mesh_terms: D000818:Animals; D004117:Dimethoate / Q000008:administration & dosage*; D004330:Drosophila / Q000187:drug effects / Q000254:growth & development*; D004331:Drosophila melanogaster / Q000187:drug effects / Q000254:growth & development; D007306:Insecticides / Q000008:administration & dosage*; D013045:Species Specificity; D013312:Stress, Physiological; D013696:Temperature
chemical_list: D007306:Insecticides; D004117:Dimethoate