Model for biological control of canalization and evolvability. In any individual the strength of signaling through Hsp90 target pathways is directly proportional to the level of Hsp90 function (top panel), but the phenotypic effects of changes in signaling strength are often highly nonlinear, creating thresholds (the inflection point, second from top).

Abstract

<div><p>A simple consequence of steep non-linearity is that sensitivity to all kinds of perturbation and stochastic effects is expected to be highest at the inflection point (second panel from bottom).</p> <p>This simple relationship between sensitivity to variation and the steepness of the signaling-phenotype relationship at the inflection point, the inverse of canalization (bottom panel), suggests why all variation increases in concert for individuals and/or populations near trait thresholds.</p></div