The developmental-genetics of canalization

Abstract

Canalization, or robustness to genetic or environmental perturbations, is fundamental to complex organisms. While there is strong evidence for canalization as an evolved property that varies among genotypes, the developmental and genetic mechanisms that produce this phenomenon are very poorly understood. For evolutionary biology, understanding how canalization arises is important because, by modulating the phenotypic variation that arises in response to genetic differences, canalization is a determinant of evolvability. For genetics of disease in humans and for economically important traits in agriculture, this subject is important because canalization is a potentially significant cause of missing heritability that confounds genomic prediction of phenotypes. We review the major lines of thought on the developmental-genetic basis for canalization. These fall into two groups. One proposes specific evolved molecular mechanisms while the other deals with robustness or canalization as a more general feature of development. These explanations for canalization are not mutually exclusive and they overlap in several ways. General explanations for canalization are more likely to involve emergent features of development than specific molecular mechanisms. Disentangling these explanations is also complicated by differences in perspectives between genetics and developmental biology. Understanding canalization at a mechanistic level will require conceptual and methodological approaches that integrate quantitative genetics and developmental biology.

Different developmental environments reveal multitrait plastic responses in South American Anostomidae fish

“…Accordingly, phenotypic plasticity induced by environmental signals might precede adaptive evolution in certain scenarios (Levis & Pfennig, 2016;Stearns, 1989;West-Eberhard, 2005), an statement supported by empirical studies describing plastic variation in particular traits as a function of specific environmental signals (Aubret & Shine, 2008;Bento et al, 2010;Brakefield et al, 1996;Sicard et al, 2014;Whitehead et al, 2012). In agreement with the idea of "developmental bias" (Hallgrimsson et al, 2019;Laland et al, 2015;Uller, Moczek, Watson, Brakefield, & Laland, 2018), intrinsic properties of developing systems may produce new phenotypes in response either to mutations or to environmental inputs. Specifically, in M. macrocephalus, we show that different environments influence developmental trajectories and reveal plastic responses that integrate morphological and behavioral variation into phenotypes that perform appropriately in conditions mimicking predator escape.…”

Phenotypes to remember: Evolutionary developmental memory capacity and robustness

“…It requires that the neighborhood (according to a given metric) of the embryonic states must also be in the basin of their corresponding adult states. Therefore, some inputs of variation should produce little or no phenotypic variation at all, a phenomenon that has received a lot of attention under the labels of canalization, robustness or buffering (Waddington, 1942;Nijhout, 2002;Hallgrimsson et al, 2019). The recovery performance of the network changes with increasing amount of perturbations (Fig.…”

Testing the evolutionary constraints of metamorphosis: The ontogeny of head shape inTriturusnewts

“…; Hallgrimsson et al. ; Takahashi ; Klingenberg ). The observed similar ontogenetic pattern of variance in Triturus species and their hybrids indicates that the same underlying mechanism of developmental canalization exists, regardless of the genetic differences between the two species or the new genetic combinations of their hybrids.…”

“…Reduced phenotypic variance should reflect canalization of development, the tendency of developmental processes to follow particular trajectories, buffer, and channel phenotypic variation (Waddington 1942(Waddington , 1953(Waddington , 1957Wagner et al 1997;Zelditch et al 2012;Hallgrimsson et al 2018;Takahashi 2019;Klingenberg 2019). The observed similar ontogenetic pattern of variance in Triturus species and their hybrids indicates that the same underlying mechanism of developmental canalization exists, regardless of the genetic differences between the two species or the new genetic combinations of their hybrids.…”