Genotype-Environment Interaction and the Evolution of Phenotypic Plasticity

Abstract

Studies of spatial variation in the environment have primarily focused on how genetic variation can be maintained. Many one-locus genetic models have addressed this issue, but, for several reasons, these models are not directly applicable to quantitative (polygenic) traits. One reason is that for continuously varying characters, the evolution of the mean phenotype expressed in different environments (the norm of reaction) is also of interest. Our quantitative genetic models describe the evolution of phenotypic response to the environment, also known as phenotypic plasticity (Gause, 1947), and illustrate how the norm of reaction (Schmalhausen, 1949) can be shaped by selection. These models utilize the statistical relationship which exists between genotype-environment interaction and genetic correlation to describe evolution of the mean phenotype under soft and hard selection in coarse-grained environments. Just as genetic correlations among characters within a single environment can constrain the response to simultaneous selection, so can a genetic correlation between states of a character which are expressed in two environments. Unless the genetic correlation across environments is ± 1, polygenic variation is exhausted, or there is a cost to plasticity, panmictic populations under a bivariate fitness function will eventually attain the optimum mean phenotype for a given character in each environment. However, very high positive or negative correlations can substantially slow the rate of evolution and may produce temporary maladaptation in one environment before the optimum joint phenotype is finally attained. Evolutionary trajectories under hard and soft selection can differ: in hard selection, the environments with the highest initial mean fitness contribute most individuals to the mating pool. In both hard and soft selection, evolution toward the optimum in a rare environment is much slower than it is in a common one. A subdivided population model reveals that migration restriction can facilitate local adaptation. However, unless there is no migration or one of the special cases discussed for panmictic populations holds, no geographical variation in the norm of reaction will be maintained at equilibrium. Implications of these results for the interpretation of spatial patterns of phenotypic variation in natural populations are discussed.

Inbreeding depression in adaptive plasticity under predation risk in a freshwater snail

“…with predators). Therefore, depending on the strength and direction of the genetic correlations among traits across environments, the evolution of plasticity may be facilitated or constrained by selection in certain environments (Via & Lande 1985). While it is known that inbreeding depression can change across environments (e.g.…”

Allopatric origins of microbial species

“…In fact, these processes directly counteract each other. Relatively high migration rates prevent local adaptation and vice versa ( Via & Lande 1985). In order to understand how the balance between in situ evolution and dispersal affects different species, we must describe the population genetic parameters that are involved in both the processes.…”

Evolutionary bet-hedging in the real world: empirical evidence and challenges revealed by plants

“…All else being equal, theory predicts that selection will act to reduce temporal variation in fitness (Cohen 1966). In environments that exhibit reliable cues about their future state, species may evolve mechanisms that allow them to respond appropriately to prevailing conditions via phenotypic plasticity (Via & Lande 1985). However, when reliable cues for predicting environmental variation at the intergenerational scale are unavailable, individuals are forced to apply a life-history strategy without 'knowing' how it will impact future fitness.…”