Presentation Detail

Evolutionary Ecology

Wood, Corlett W. [1], Brodie III., Edmund [1].

Evolutionary response when selection and heritability covary.

The environment is known to affect two key drivers of adaptive trait evolution: the strength of selection on a trait, and the amount of heritable variation in that trait. Variation in the strength and direction of selection is common across taxa, and evidence is accumulating that environmental quality, stressfulness, and novelty all affect the abundance of heritable variation. As a result, environmental heterogeneity has the potential to generate an association between selection and heritable variation in natural populations. This covariance could substantially alter basic evolutionary dynamics, accelerating evolution if genetic variation is abundant in the same environments that generate strong selection, and forestalling evolutionary change if selection is strong only when heritable variation is scarce. Although this covariance has been shown to significantly alter the response to selection in the wild, the current deficit of quantitative predictions makes it difficult to broadly assess its ramifications for trait evolution in natural populations. Here we explore the evolutionary consequences of covariance between selection and heritable variation. First, we draw on probability theory to generate quantitative predictions of the effect of this covariance on the mean and variance of the response to selection. Second, to evaluate the degree to which this phenomenon may accelerate or arrest trait evolution in the wild, we take a modeling approach that incorporates known distributions of selection and heritable variation in natural populations. We simulated replicate populations composed of 1000 subpopulations with a specified covariance between selection and heritable variation, and calculated the response to selection in each subpopulation. We found that this covariance has a moderate effect on the mean and dramatically alters the variance of the response to selection in these simulated populations. Finally, we synthesize existing empirical estimates of the covariance between selection and heritable variation to predict its likely magnitude and direction under field conditions. These results have wide-ranging implications for evolution in heterogeneous environments. Covariance between selection and heritable variation may contribute to the perennial difficulty of predicting trait evolution in the wild, and partially account for microevolutionary stasis in the face of strong selection. Furthermore, this phenomenon may constitute an unappreciated mechanism that maintains variation in quantitative traits if negative covariance between the two parameters is common. Understanding the factors that constrain and facilitate adaptive evolution under dynamic environmental conditions is critical to characterizing species' potential to respond to selection, particularly in the context of emerging challenges such as climate change.

1 - University of Virginia, Biology, 485 McCormick Road, Charlottesville, VA, 22904, USA

Keywords:
Response to selection
heterogeneous environment
additive genetic variation.

Presentation Type: Regular Oral Presentation
Session: 66
Location: Alpine C/Snowbird Center
Date: Sunday, June 23rd, 2013
Time: 11:00 AM
Number: 66003
Abstract ID:743
Candidate for Awards:W.D. Hamilton Award for Outstanding Student Presentation