The alignment between phenotypic plasticity, the major axis of genetic variation and the response to selection

Abstract

Phenotypic plasticity is the ability of a genotype to produce more than one phenotype in order to match the environment. Recent theory proposes that the major axis of genetic variation in a phenotypically plastic population can align with the direction of selection. Therefore, theory predicts that plasticity directly aids adaptation by increasing genetic variation in the direction favoured by selection and reflected in plasticity. We evaluated this theory in the freshwater crustacean Daphnia pulex, facing predation risk from two contrasting size-selective predators. We estimated plasticity in several life-history traits, the G matrix of these traits, the selection gradients on reproduction and survival, and the predicted responses to selection. Using these data, we tested whether the genetic lines of least resistance and the predicted response to selection aligned with plasticity. We found predator environment-specific G matrices, but shared genetic architecture across environments resulted in more constraint in the G matrix than in the plasticity of the traits, sometimes preventing alignment of the two. However, as the importance of survival selection increased, the difference between environments in their predicted response to selection increased and resulted in closer alignment between the plasticity and the predicted selection response. Therefore, plasticity may indeed aid adaptation to new environments.

Characterizing morphological (co)variation using structural equation models: Body size, allometric relationships and evolvability in a house sparrow metapopulation

“…This suggests that plasticity may aid adaptive phenotypic integration, and that both genetic and (permanent) environmental factors in this system tend to affect morphometric characters through similar physiological pathways (Pigliucci ; Lind et al. ).…”

“…Importantly, the rela-tively consistent results from the SEM, as applied to the genetic and environmental covariation in the present study, indicate that the PE matrix partly aligns with the G matrix. This suggests that plasticity may aid adaptive phenotypic integration, and that both genetic and (permanent) environmental factors in this system tend to affect morphometric characters through similar physiological pathways (Pigliucci 2001a;Lind et al 2015).…”

The predictability and magnitude of life‐history divergence to ecological agents of selection: a meta‐analysis in livebearing fishes

“…Thus, even divergence mediated by developmental plasticity may often reflect the initial stages of evolved divergence (Lind et al . , but see Ghalambor et al . ).…”

“…S2). However, evidence for plasticity's role in mediating evolved differences is rapidly growing (West-Eberhard 2003;Lind et al 2015), and, in many cases, genetic divergence to selective agents may have begun as plastic responses before becoming fixed via genetic accommodation (e.g. Schlichting & Wund 2014).…”

“…Schlichting & Wund 2014). Thus, even divergence mediated by developmental plasticity may often reflect the initial stages of evolved divergence (Lind et al 2015, but see Ghalambor et al 2015). Future research should nonetheless evaluate the relative roles of plastic and genetic differences underlying predictable divergence to multiple selective agents.…”