Ian Dworkin

Are canalizing mechanisms contributing to evolutionary change as frequently as we think? Or at all?

McMaster University, Canada

e-mail: dworkin@mcmaster.ca

Changes in mechanisms that modulate phenotypic expression, collectively referred to as canalization, are often invoked to account for rapid evolutionary changes, specifically for related to changes of phenotypic plasticity or genetic assimilation of traits. Waddington originally related models of canalization to changes in ‘epigenetic landscapes”. Waddington’s original view of such landscapes was notably, and possibly necessarily, abstract, remaining a subject of much confusion. There have been notable advancements in theoretical and empirical understanding of genetic, cellular, and developmental mechanisms modulating phenotypic expression of traits, influencing patterns of within and among-individual variation. At the same time, research has shown distinctions between robustness to environmental and genetic perturbations. This suggests considerably more diversity in mechanism and outcome than Waddington first described in relations to canalization. Despite this, canalization per se, is often invoked when there are evolved changes in plasticity, loss or gain of genetic assimilation among other forms of phenotypic evolution. In this talk, I will use examples from research in our lab, and beyond, to discuss whether canalization needs to be invoked at all as an explanation for such findings. I will argue that we should focus on  specifics of mechanisms across various systems, to determine whether there are generalities, and whether canalizing mechanisms are likely the predominant mechanism explaining evolutionary changes in these systems.  I will end with a brief discussion on whether we should abandon the abstractions of canalization in favour of (in the short term) cataloging the various mechanisms that modulate phenotypic expression, or whether the abstractions remains informative.