A central problem in evolutionary quantitative genetics has been to attempt to dissect the genetic basis of complex traits. A variety of inferential methods have been developed to probe this issue. Here, I use experimental evolution, next generation sequencing and standing genetic variation in the nematode Caenorhabditis remanei to dissect the genetic basis of two model complex traits: oxidative and heat stress response.
Pleiotropy, when one gene affects more than one trait, is an important phenomenon to understand when attempting to understand the genetic architecture of a complex trait. Previous work in the nematode C. elegans found that abiotic stress response is controlled by a handful of genes of major effect, and that mutations in one gene can affect the ability of the organism to respond to multiple types of stressors. I used experimental evolution to probe the extent of pleiotropy between the genes selected for resistance to one of two abiotic stressors: acute heat and oxidative. In contrast to expectations, I find that acute heat stress response and acute oxidative response are polygenic, complex traits. Additionally, I find that the evolved responses do not share a genetic basis. This lack of correlation is reflected at the levels of phenotype, gene expression and genomic response to selection.
In addition to the complex interactions within an organism, the genetic architecture of complex traits and response to selection are affected by population dynamics. Here, I investigate the effect of gene flow on patterns and extent of phenotypic and genetic divergence between populations in distinct environments—a standard lab environment and a chronic heat stress environment. Gene flow of lab-adapted individuals into chronic heat stress adapted populations did not affect phenotypic adaptation, but greatly decreased the number of genomic sites that responded to selection. These results fit predictions that gene flow of non-locally adapted individuals will create an additional barrier for local adaptation, and the strength of selection of locally adapted alleles must not only be greater than the strength of random effects, but also be stronger than the effects of gene flow.
This work includes unpublished co-authored material.
|Advisor:||Phillips, Patrick C.|
|Commitee:||Conery, John, Cresko, William, Harms, Michael, Streisfeld, Matthew|
|School:||University of Oregon|
|School Location:||United States -- Oregon|
|Source:||DAI-B 79/12(E), Dissertation Abstracts International|
|Subjects:||Evolution and Development|
|Keywords:||Caenorhabditis remanei, Complex rraits, Genetic architecture, Nematode|
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