Effective Population Size and the Efficacy of Selection on the X Chromosomes of Two Closely Related Drosophila Species

摘要: The prevalence of natural selection relative to genetic drift is central interest in evolutionary biology. Depending on the distribution fitness effects new mutations, importance these forces may differ species with different effective population sizes. Here, we survey variation at 105 orthologous X-linked protein coding regions Drosophila melanogaster and its sister D. simulans, two closely related distinct demographic histories. We observe significantly higher levels polymorphism evidence for stronger codon usage bias consistent a larger historical size average this species. Despite differences, estimate that <10% newly arising nonsynonymous mutations have deleterious nearly neutral range (i.e., -10 < N(e)s 0) both inferred distributions models translate into surprisingly high estimates fraction "adaptive" divergence (∼ 85-90%). histories, differences apparently played little role dynamics evolution species, adaptive (α) remain even if account recent 10-fold growth. Furthermore, although several studies noted strong signatures recurrent genes involved immunity, reproduction, sexual conflict, intragenomic our finding randomly chosen proteins (with respect function) suggests many other factors likely contribute signature Drosophila.