PgmNr P373: The correlation across populations of mutation effects on fitness.

Authors:
Ryan Gutenkunst; Alec Coffman; Aaron Ragsdale; PingHsun Hsieh


Institutes
University of Arizona, Tucson, AZ.


Abstract:

Divergent selection, in which the same allele has different effects on fitness in different populations, drives environmental speciation. Much is known about patterns of genetic variation near loci with given divergent selection coefficients, but little is known about overall genomic patterns of divergent selection. To fill this gap, we developed a framework for inferring the joint distribution of fitness effects (DFE) between pairs of populations, based on a diffusion approximation to the joint allele frequency spectrum. We applied this framework to African and American populations of Drosophila melanogaster, first estimating demographic history and then the joint DFE. As expected, we found that genome-wide nonsynonymous mutation fitness effects were highly correlated between these two populations. Considering functional subsets of genes, however, revealed striking differences. For example, for muscle development genes the joint DFE has a correlation of roughly zero, whereas for neuronal development genes it is almost one. Divergent selection in these populations is thus operating much more strongly on the musculature than the brain, suggesting that adaptation is primarily physiological rather than behavioral. Future work will apply this general framework to other populations and species, thus quantifying how divergent selection varies with environmental and molecular context.