  We derive an expression for the variation between parallel trajectories in
phenotypic evolution, extending the well known result that predicts the mean
evolutionary path in adaptive dynamics or quantitative genetics. We show how
this expression gives rise to the notion of fluctuation domains - parts of the
fitness landscape where the rate of evolution is very predictable (due to
fluctuation dissipation) and parts where it is highly variable (due to
fluctuation enhancement). These fluctuation domains are determined by the
curvature of the fitness landscape. Regions of the fitness landscape with
positive curvature, such as adaptive valleys or branching points, experience
enhancement. Regions with negative curvature, such as adaptive peaks,
experience dissipation. We explore these dynamics in the ecological scenarios
of implicit and explicit competition for a limiting resource.
