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The Genetic Basis of Physical Traits

Traits can evolve in response to selection from the environment only when traits have a genetic basis. Thus, the genetic and developmental architecture of traits are highly relevant for the outcome of selection. Most basically, in order for a trait to evolve in response to selection from the environment, there must be some degree of genetic variation in that trait (the measure of which we call heritability). And, the more genetic variation (the higher the heritability), the greater the likelihood for that trait to evolve if the environment changes.

It is more complex than that, however, because often traits are plastic, meaning they may be expressed differently in different environments. Furthermore, there can be genetic variation in plasticity—also known as genotype x environment interactions—which means that different genotypes may have very different plastic responses to environmental change. 

A theme throughout our research is understanding the genetic underpinnings of phenotype as the driver of evolutionary change. We look at genetic variation in traits, genetic variation in plasticity, and genetic correlations between traits that co-evolve.

 

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Evolutionary responses to environmental change can only occur through changes in the genetics. Therefore, a theme throughout our research is understanding the genetic underpinnings of phenotype as the vehicle for evolutionary change. We implement classic quantitative genetics breeding designs to tease apart the effects of genetics versus the environment in shaping phenotypic variation. Understanding the magnitude of genetic variation underlying phenotype allows us not only to better understand how selection has shaped traits, but also the potential for evolutionary response to change.

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Genotype x Environment Interactions

Understanding the genetic and developmental architecture of sexual traits can provide important insight into the evolution of sexual traits and speciation. The expresion of sexual traits (e.g., male signals and female mate preferences) are shaped by genetics and the environment. However, a third source of variation in these traits is also important: genetoype by environment interactions (GxE). GxE arises when different genotypes respond to environmental variation in a different way. Also referred to as genetic variation in plasticity, understanding GxE ... For example, with global warming

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Genetic correlations among traits

In many organisms, sexual traits and preferences show patterns of tight correspondence across populations and closely related species. This apparent coevolution of traits and preferences can produce divergence among species, eventually leading to reproductive isolation. However, the mechanisms generating these coevoluationary patterns is still poorly understood. One mechanism was proposed by R.A. Fisher in 1933 (year?): selection on male traits by female preference will generate a genetic coupling between the trait and preference, as sons will bear the favored traits and daughters the preference. This phenomenon should occur any time there is genetic variation present in both signal and preference, and there is selection on the male signal. 

When selection on one trait influences the evolution of another trait through indirect selection, genetic covariance is generated...


Genetic variation in traits

Selection can only have an effect on phenotype is a trait is heritable—that is, if that trait has underlying genetic variation, or genetic differences among individuals account for part of the variation in phenotype expressed. We study heritability because we are interested in two questions. First, how strong has past selection been on a given trait? Low heritabilty suggests strong selection removing individuals with less favorable phenotypes. Second, how will phenotype respond to changes in selection? With high heritability, selection can lead to a change in phenotype. By understanding these two facets of variability in traits, we can assemble a better picture of why a trait is the way it is today, and how it might respond when the environment changes. One project is the temperature experiment (with link to this project?) [might also talk about how genetic variaiton in sexual traits is an assumption of most models of sexual selection, and that ties into my 2015 paper]