Evolutionary analyses of D. melanogaster autosomal genes and systems of selection. (A) The ratios of nonsynonymous substitution rate to synonymous substitution rate (dN/dS) across different gene expression groups. Diploid (purple) and haploid (green) groups were considered those genes overexpressed in mitosis, and meiosis or post-meiosis, respectively (Methods). Total sample sizes of diploid and haploid genes were 2348 and 2212, respectively, for dN/dS. Mann-Whitney-Wilcoxon test was used as the statistical test: (***) P < 0.001. (B) Haploid selection advantage over diploid selection is shown as haploid cells (green) carrying new allele a immediately present a new phenotype (dark green). However, for diploid cells (purple), heterozygote cells do not present a different phenotype (all light purple). The new allele a effect is hidden by the dominant allele A (dashed red arrow).
