Cryptic Evolution: Does Environmental Deterioration Have a Genetic Basis?

Abstract

Cryptic evolution has been defined as adaptive evolutionary change being masked by concurrent environmental change. Empirical studies of cryptic evolution have usually invoked a changing climate and/ or increasing population density as the form of detrimental environmental change experienced by a population undergoing cryptic evolution. However, Fisher (1958) emphasized that evolutionary change in itself is likely to be an important component of ''environmental deterioration,'' a point restated by Cooke et al. (1990) in the context of intraspecific competition. In this form, environmental deterioration arises because a winning lineage has to compete against more winners in successive generations as the population evolves. This ''evolutionary environmental deterioration'' has different implications for the selection and evolution of traits influenced by resource competition than general environmental change. We reformulate Cooke's model as a quantitative genetic model to show that it is identical in form to more recent developments proposed by quantitative geneticists. This provides a statistical framework for discriminating between the alternative hypotheses of environmental change and environmental deterioration caused by evolutionary change. We also demonstrate that in systems where no phenotypic change has occurred, there are many reasonable biological processes that will generate patterns in predicted breeding values that are consistent with what has been interpreted as cryptic evolution, and care needs to be taken when interpreting these patterns. These processes include mutation, sib competition, and invisible fractions.

Successful by Chance? The Power of Mixed Models and Neutral Simulations for the Detection of Individual Fixed Heterogeneity in Fitness Components

“…First, a phenotypic response to selection on components of fitness is not necessarily expected. For example, environmental deterioration, which may be the result of an increase in mean competitiveness (Fisher 1958;Hadfield et al 2011), may mask a genetic change. Second, only the additive genetic part of the variation can respond to selection, and genetic variation may be renewed through migration, mutations, and balancing selection (Fisher 1958;Charlesworth 2015).…”

Competition as a source of constraint on life history evolution in natural populations

“…Under this scenario, directional selection on individual growth will cause correlated evolution of a more competitive environment. This phenomenon, termed 'evolutionary environmental deterioration' (Fisher, 1958) or the 'treadmill of competition' (Wolf, 2003), arises because as a population evolves a winning lineage finds itself competing against more and more winners in each successive generation (Hadfield et al, 2011). The social environment 'deteriorates' with each generation, a change that offsets the increase in mean growth rate predicted by the breeder's equation (Fisher, 1958;Cooke et al, 1990;Frank and Slatkin, 1992).…”

“…However, the view that competition contributes only environmental variance may be overly simplistic if among-individual variation in competitive ability itself has a genetic component Bijma and Wade, 2008;Hadfield et al, 2011). In this case, genetic influences on focal phenotype can arise not just from an individual's own genes (direct genetic effects), but also from genes present in the competitive environment provided by others-so-called associative (Griffing, 1967(Griffing, , 1976 or indirect genetic effects (IGEs; Moore et al, 1997).…”

“…Here I pose the question: are IGEs an important source of evolutionary constraint for resourcedependent traits in natural populations? Existing theory tells us that they could be (Hadfield et al, 2011), but we currently have little idea of how prevalent or large genetically determined competitive effects are. Consequently, we cannot know to what extent competitionwhich is fairly ubiquitous in natural populations-may contribute to the frequent observation of phenotypic stasis for heritable traits under directional selection (Cooke et al, 1990;Merilä et al, 2001).…”

The quantitative genetics of indirect genetic effects: a selective review of modelling issues

“…In this perspective, IGEs create an environment that can respond to selection (for example, Hadfield et al, 2011). Thus, in the context of the classical quantitative genetic model where the trait value of an individual is decomposed into the heritable effect of its genotype and a residual labelled as environment, P ¼ G þ E, the E-term is partly heritable when IGEs occur.…”