Understanding the fitness consequences of correlated shifts in ecological parameters is a central challenge in contemporary biology. We studied two genotypes of the waterflea, Daphnia pulex that exhibit striking genotype x environment (GxE) interaction in response to shifts in phosphorus (P) supply, which also alters dietary carbon (C) content. Genotype1 (G1) had higher fitness under a LoC:HiP (C:P~100) diet, while Genotype2 (G2) performed better in C:P~800 diet. Dual 14C/33P radiotracer assays clearly show that this GxE interaction is driven by physiological differences in the processing of C and P. G1 was more efficient in C processing, while G2 was more efficient in P use. Microarrays revealed that the genotypes differed in the expression of 6057 genes. Most of these genes were involved in pathways already known to be sensitive to stoichiometric imbalances. Our study provides the first step to couple functional genomics with ecologically explicit frameworks to understand the complexity of processes underlying GxE interactions.
Overall design
2 genotypes of Daphnia pulex, two dietary treatments (high and low phosphorus Scenedesmus algal, C:P= 100, and 800, respectively), exposed 6hours and 3days
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