TanyaPhung_TAGC16_final.pptx (6.47 MB)
Examining the effect of natural selection on linked neutral divergence
Version 2 2016-07-26, 01:07
Version 1 2016-07-21, 15:28
presentation
posted on 2016-07-26, 01:07 authored by Tanya PhungTanya PhungThis is the slide for my talk that I presented this talk at The Allied Genetics Conference in Orlando, Florida in July 2016.
Abstract: A
major goal in evolutionary biology is to understand the processes
that shape patterns of genetic variation across genomes. One process
that has received a lot of attention is natural selection. In
particular, numerous studies in a variety of species have shown that
neutral genetic diversity (intra-species differences) has been
reduced at sites linked to those under selection. However, the effect
of selection on neutral sequence divergence (inter-species
differences) remains ambiguous. While some empirical studies have
reported correlations between divergence and recombination which is
interpreted as empirical evidence for natural selection reducing
neutral linked divergence, theoretical arguments argued otherwise,
especially for species that have diverged long ago. Here we address
these outstanding issues by examining how natural selection has
affected divergence between both closely and distantly related
species. We show that neutral divergence is negatively correlated
with functional content and positively correlated with estimates of
background selection from primates, which is a measure of how
negative selection affects linked neutral sites. These patterns
persist even when comparing humans and mice, species that split 75
million years ago. Coalescent models indicate that background
selection can generate these patterns, suggesting that natural
selection has affected linked divergence between distantly related
species. Our theoretical and simulation results show that even when
the contribution of ancestral polymorphism to divergence is small,
background selection in the ancestral population can still explain a
large proportion of the variance in divergence across the genome.
Thus, the view that selection does not affect divergence at linked
neutral sites needs to be reconsidered. These findings also suggest
that the effects of natural selection affecting linked neutral sites
cannot be ignored when studying neutral divergence. Our work has
important implications for understanding evolution of genomes and
interpreting patterns of genetic variation.