Genetic Consequences of Biologically Altered Environments

Abstract

Evolvable traits of organisms can alter the environment those organisms experience. While it is well appreciated that those modified environments can influence natural selection to which organisms are exposed, they can also influence the expression of genetic variances and covariances of traits under selection. When genetic variance and covariance change in response to changes in the evolving, modified environment, rates and outcomes of evolution also change. Here we discuss the basic mechanisms whereby organisms modify their environments, review how those modified environments have been shown to alter genetic variance and covariance, and discuss potential evolutionary consequences of such dynamics. With these dynamics, responses to selection can be more rapid and sustained, leading to more extreme phenotypes, or they can be slower and truncated, leading to more conserved phenotypes. Patterns of correlated selection can also change, leading to greater or less evolutionary independence of traits, or even causing convergence or divergence of traits, even when selection on them is consistent across environments. Developing evolutionary models that incorporate changes in genetic variances and covariances when environments themselves evolve requires developing methods to predict how genetic parameters respond to environments—frequently multifactorial environments. It also requires a population-level analysis of how traits of collections of individuals modify environments for themselves and/or others in a population, possibly in spatially explicit ways. Despite the challenges of elucidating the mechanisms and nuances of these processes, even qualitative predictions of how environment-modifying traits alter evolutionary potential are likely to improve projections of evolutionary outcomes.

Does the definition of a novel environment affect the ability to detect cryptic genetic variation?

“…To investigate this, we compared “extreme” novelty, arising from change in a condition already present in a population's ancestry (Chevin & Hoffmann, 2017) to “absolute” novelty arising from a condition not experienced previously (Diamond & Martin, 2016; Snell‐Rood et al., 2018). As an extension of ancestral environments, we predicted that extreme novel environments would generate less genetic variation than absolute novel environments (Chevin & Hoffmann, 2017; D'Aguillo et al., 2022; Parsons et al., 2020; Radersma et al., 2020; Uller et al., 2018). In contrast, we predicted that absolute novel environments would induce a greater range of phenotypes due to insufficient time for natural selection to shape an adaptive plastic response (Alvarez et al., 2021; Auge et al., 2017; Chevin et al., 2010; Hoyle & Ezard, 2012).…”

“…Rather than a static feature of genotypes, accumulating evidence suggests that the contemporary environment can influence within‐generation expression of genetic variance (D'Aguillo et al., 2022; Hoffmann & Merilä, 1999; Stearns et al., 1991). This environment‐dependant variance arises when genotypes respond in different ways to an environmental change, known as a genotype‐by‐environment interaction (G × E; Saltz et al., 2018; Via & Lande, 1985, 1987).…”

“…Consequently, there is less variation in how genotypes respond to the environment, reducing G × E and the genetic variance available to selection (Arnold & Wade, 1984;Falconer & Mackay, 1996;Oostra et al, 2018). In contrast, novel environments that were rare or absent from a population's evolutionary history are hypothesized to increase G × E and the genetic variance available to selection; with genotypes exhibiting unrefined and more variable responses to the environment (Charmantier & Garant, 2005;Rutherford & Lindquist, 1998;Schlichting, 2008;Snell-Rood et al, 2018) and pre-existing differences amplified (D'Aguillo et al, 2019(D'Aguillo et al, , 2022. This increase in variation is known as the release of cryptic genetic variation (CGV); genetic variation is only expressed under atypical conditions that are rare or absent in the evolutionary history of a population.…”

Genotype by Environment Interaction on Early-Maturing and High-Yield Maize Hybrids

“…The combined analysis of variance (ANOVA) for harvest age and grain yield per hectare on ten genotypes in 14 research locations (seven locations, two seasons) revealed that genotypes, environments (season, location, season × location), and interactions (genotype × season, genotype × location, genotype × season × location) significantly affect harvest age and grain yield per hectare (p < 0.01) (as shown in Table 3). As a factor, genotypes resulted in a significant influence since the tested materials had different genetic backgrounds [36,37]. The combined ANOVA results revealed that genetics, environment, and interactions were the main determinants of harvest age and grain yield per hectare.…”

Changes in phenology can alter patterns of natural selection: the joint evolution of germination time and postgermination traits

“…This reduction in environmental variation can accelerate adaptation to the selected habitat (Whitlock, 1996), alter rates of adaptation by altering genetic parameters (e.g. heritability, pleiotropy, and epistasis) that are sensitive to environmental conditions (Saltz & Nuzhdin, 2014; D'Aguillo et al ., 2022), or lead to specialization of traits (Evans & Cabin, 1995; Whitlock, 1996; Donohue, 2003). Specialized traits, in turn, can favor more precise selection of the habitat to which those traits are specialized (Ravigné et al ., 2009), thus leading to evolutionary feedbacks, which predict associations between habitat tracking and specialization (Evans & Cabin, 1995).…”