RT Journal Article
SR Electronic
T1 How much does <em>N</em><sub><em>e</em></sub> vary among species?
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 861849
DO 10.1101/861849
A1 Nicolas Galtier
A1 Marjolaine Rousselle
YR 2019
UL http://biorxiv.org/content/early/2019/12/06/861849.abstract
AB Genetic drift is an important evolutionary force of strength inversely proportional to Ne, the effective population size. The impact of drift on genome diversity and evolution is known to vary among species, but quantifying this effect is a difficult task. Here we assess the magnitude of variation in drift power among species of animals via its effect on the mutation load – which implies to jointly infer the distribution of fitness effects of deleterious mutations (DFE). To this aim, we analyze the non-synonymous (amino-acid changing) and synonymous (amino-acid conservative) allele frequency distributions in a large sample of metazoan species, with a focus on the primates vs. fruit flies contrast. We show that a Gamma model of the DFE is not suitable due to strong differences in estimated shape parameters among taxa, while adding a class of lethal mutations essentially solves the problem. Using the Gamma + lethal model and assuming that the mean deleterious effects of non-synonymous mutations is shared among species, we estimate that the power of drift varies by a factor of at least 500 between large-Ne and small-Ne species of animals, i.e., an order of magnitude more than the among-species variation in genetic diversity. Our results therefore contribute to addressing Lewontin’s paradox, while further questioning the meaning of the Ne parameter in population genomics.