Quantitative genetics of phosphorus content in the freshwater herbivore, Daphnia pulicaria

1. Phosphorus (P) is essential for growth of all organisms, and P content is correlated with growth in most taxa. Although P content was initially considered to be a trait fixed at the species level, there is growing evidence for considerable intraspecific variation. Selection on such variation can thus alter the rates at which P fluxes through food webs. 2. Nevertheless, prior work describing the sources and extent of intraspecific variation in P content were not genetically explicit, confounded by unknown genetic background and evolutionary history. We constructed an F2 recombinant population of the dominant freshwater grazer, Daphnia pulicaria to mitigate such issues. 3. F2 recombinants exhibited considerable variation in growth rate, P content (0.49% to 1.97%), P use efficiency (PUE; 51 to 208 mg biomass/mg P), and correlated traits such as hatching time of resting eggs, in common garden conditions. 4. These results clearly demonstrate the scope of genetic recombination in ...