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Tuesday, April 24 • 12:00pm - 1:30pm
Phylogenetic Comparative Analysis Of DNA Methylation Rates In Reptiles

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In addition to playing a role in genomic function, DNA methylation influences evolution by regulating transcription. Technological advances, such as High-Performance Liquid Chromatography (RP-HPLC), have allowed scientists to explore genomic regulatory changes that contribute to species diversity and phenotypic variability. Epigenetic modifications of notable interest include 5-methylcytosine (5mC) and CpG (GC), as they are related to neutral selection on the cellular level. To understand how these regulatory changes evolve in a phylogenetic context, we analyzed these quantitative traits phylogenetically by mapping them to a mitochondrial phylogeny inferred de novo across 28 reptile species. Previous studies in reptiles concluded that there was no significant correlation between DNA methylation and environmental stimuli, but these studies did not correct for the non-independence of evolutionarily related species and thus violated a fundamental statistical assumption. To model these traits, we corrected these traits and ran phylogenetic comparative analyses in RStudio®. First, we examined the extent of the phylogenetic non-independence problem by estimating measures of phylogenetic signal for each quantitative trait. We then repeated regressions from a previous study, following phylogenetic correction, and inferred correlation between our two epigenetic modifications. Finally, we fit a series of evolutionary models to examine the evolution of these traits across the reptile phylogeny and selected the best model using an AICc model selection procedure. We found phylogenetic signal in GC but not 5mC, and that phylogenetic correction did not affect results, likely owing to the relatively small number of tips and the lack of phylogenetic signal in one of the traits. The evolution of these traits is best approximated by an Ornstein-Uhlenbeck model, suggesting that local optima exist for these quantitative characters and predicting a loss of phylogenetic signal (convergence or homoplasy). This study is important because the results can be used to understand the modifications to the genome influencing phenotypic diversity.


Tuesday April 24, 2018 12:00pm - 1:30pm PDT
Sherrill Center Concourse

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