Many organisms have evolved the ability to respond to changing environmental conditions by altering development to produce different, adaptive phenotypes. Such developmental plasticity can be highly advantageous, allowing individuals within populations to adjust to changing environmental circumstances on short, non-evolutionary time scales. Considerable study has addressed the factors that promote the evolution of plasticity versus genetic adaptation as well as the potential costs and limits of plasticity. These studies have greatly advanced our understanding of the ecological and evolutionary role of plasticity. Far less understood, however, are the molecular and physiological mechanisms that underlie the determination and differentiation of different plastic phenotypes. I will discuss recent work in our lab investigating the epigenetic basis of the pea aphid wing plasticity, in which winged or wingless morphs are produced in response to a high or low-density maternal environment, respectively. These two morphs are genetically identical, yet display dramatically different phenotypes. In particular, I will present what we have learned so far about the different chromatin states that underlie the winged versus winged morphs.
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