Affiliations: 1) Institute of Population Genetics, University of Veterinary Medicine (Vetmeduni), Vienna, Austria; 2) Vienna Graduate School of Population Genetics, Vienna, Austria
Keywords: Other (Phenotypic plasticity)
Phenotypic plasticity is the phenomenon of genetically identical individuals producing different phenotypes in response to the environment. Plasticity is frequently considered to be beneficial as it helps to survive changes in the environment - particularly in the context of local adaptation. Here, we approach plasticity from a different angle. Rather than asking how plasticity contributes to local adaptation, we study a globally plastic trait and ask to what extent the underlying mechanisms are shared between populations from three different continents. Density is one such trait and larval density, particularly in holometabolous insects such as Drosophila, has been shown to vary with the availability of food and affects many life-history traits, growth rate, body size etc. We used gene expression to study the mechanistic basis of phenotypic plasticity in response to larval crowding in Drosophila simulans. As expected, larval density results in highly plastic gene expression pattern in all three populations - more than 1400 genes exhibited significant gene expression differences. 42% of the differentially expressed genes were population specific. Even when we consider functionally similar genes (based on GO category), 78.8% (460) of the differentially expressed population specific genes reflect a functional divergence among local populations. We conclude that plastic traits shared among populations have experienced re-wiring of their mechanistic basis for example by directing one type of stress response towards a different stress. This suggests that the comparison of diverged natural populations may provide an excellent approach to understand how the regulatory network of conserved traits could evolve between species.