Predator induced phenotypes are inherited over four generations in genetically identical Daphnia lumholtzi

Environmental variation can induce phenotypic changes through adaptation of populations and acclimation of individuals. Whereas adaptation can lead to persistent changes within a population via allele frequency shifts, induced plastic phenotypes have been thought to be ephemeral and lasting only through the affected generation. A growing number of studies have shown that induced phenotypes may be inherited, but it is unclear how persistent the inheritance of induced plastic phenotypes is across organisms. To directly address these questions, we measured the phenotypic effects of exposure to a predator cue in the water flea, Daphnia lumholtzi, which reproduces clonally allowing the isolation of the effects of direct environmental exposure from allelic variation. We measured the phenotypic effects of exposure to fish conditioned media in the F0, F3, F4, and F5 generations of genetically identical generations following cue exposure only in the F0 generation. We found evidence of predation induced morphologies into the F4 generation, with phenotypes receding in the F5 generation, four generations after cue removal. These results highlight the importance of the interaction between current and ancestral environments in determining phenotypic variation and highlights the importance in future studies of characterizing the molecular mechanisms of within and transgenerational phenotypic plasticity.