User:Srproulx
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Stephen Proulx Department of Ecology and Evolution (and marine biology)
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Research in the Proulx lab focuses on developing theoretical frameworks to understand the fundamental processes involved in evolution. We use a variety of empirical data to inform and test our models. In the lab, we take the experimental evolution approach to test fundamental aspects of evolution and to develop new ideas about how evolution operates in nature.
Theoretical Principles of Evolution
All living things are shaped by the events of the past. Their evolutionary history determines both the traits that we see in them today, and their ability to respond to natural and artificial selection. The past evolutionary pressure on genome structure has created organisms that are more or less sensitive to perturbations in the environment and mutations in their own genetic code. Our research has focused on some of the fundamental aspects of the evolutionary process.
A major aspect of our research program has been to consider how variable conditions alter the evolutionary process. We know that organisms face an environment that is always changing, that their competitors evolve and respond behaviorally, and that conditions vary from place to place. Each of these factors can alter the way that natural selection operates. A current research interest is the evolution of transcription control in response to fluctuating environments and the evolution of genetic architecture in response to migration between habitats.
Experimental Evolution and the Genetics of Adaptation
We take an experimental evolution approach to understand the outcome of selection at the genetic and phenotypic level. Ongoing work examines the evolution of phenotypic plasticity and maternal effects in the nematode C. elegans and the evolution of sporulation strategies in the yeast S. cerevisiae.
Gene Networks and Transcription Regulation
No gene is an island. All genes interact with other genes and gene products to produce the observable traits that determine fitness and allow natural selection to operate. Recent empirical advances have allowed the large scale exploration of genetic interactions through protocols such as microarrays, high throughput genetic interaction approaches, and the yeast two-hybrid assay. At the same time ecologists have been producing datasets with interactions between large numbers of species. These kinds of datasets can be characterized mathematically as networks because they involve interactions of varying strengths between a group of similar ``nodes.
I have analyzed the application of the network approach to both ecological and evolutionary problems and explored how network analysis techniques taken from social sciences and physics can be applied to these biological problems. One of the major challenges in this area is to understand how genetic networks come to have the patterns that we observe. Will natural selection tend to cause gene networks to have power law degree distributions? Will robustness evolve as a general feature of these networks? I have developed analytical models to determine the opportunity for canalizing selection to create robust gene networks. The conclusion of these studies is that genetic robustness is unlikely to evolve through direct selection unless a large number of genes can be buffered by a single gene. Environmental robustness, on the other hand, can easily evolve even if it is controlled by a single gene.
In order to understand how patterns arise in genetic networks we must understand where new genes come from and are how they are inserted into the existing genetic network. In particular, the adaptive landscape plays a critical role in determining the likelihood of gene duplication and the time required for duplication or subfunctionalization. The longstanding explanation for gene duplication is that redundancy between duplicate gene pairs allows the divergence of gene function. This restrictive model is a slow, partially neutral process. I have approached this problem by asking how natural selection can lead to gene duplication and have shown that genetic divergence is selected for under largely similar conditions regardless of how many gene copies there are. My work has shown that adaptive forces can lead to the rapid formation of gene families and the evolution of novel genetic function. I have extended my framework to include both changes in coding and regulatory regions and found that a form of stochastic tunneling can allow genetic variation necessary for adaptive duplication to accumulate even when the intermediate steps are not positively selected.
Sexual Selection, Sex Allocation, and Reproductive Strategies
Mate choice can have profound impacts on gene flow between populations and on adaptation to local conditions. We have investigated a number of processes that can both select for changes in the mating system and feedback onto the ecological dynamics of species. We have shown that sexual selection can improve local adaptation and that local adaptation can maintain male displays and resolve the paradox of the lek. The specific nature of mate choice is also important, and we have shown that assortative mating has different selection strength than female preferences for high quality males. We are continuing to work on the interplay between local adaptation, mate choice, and the evolution of genetic architecture.
