Molecular evolution by male reproductive tissue and spermatogenesis stage. (A) Mouse male reproductive tract and spermatogenesis cell types ordered from earliest to latest developmental stages. Numbers represent median d_N/d_S values for each tissue- or cell type with gene counts in parentheses. Coagulating gland was excluded because data were only available for one gene in this tissue. The box on the scale indicates the median phylogeny-wide d_N/d_S (0.12) across all genes, and (*) indicate significant differences from this median d_N/d_S (Wilcoxon rank-sum test FDR-corrected p < .05). (B) Proportion of genes enriched in each cell type with evidence for positive selection based on BUSTED model-averaged p-values. The dotted line represents the proportion of genes with evidence for positive selection out of all genes included in the test for selection (no cell types were significantly different from the genome-wide average; FDR-corrected Pearson’s chi-squared p > .05). (C) Proportion of genes enriched in each cell type that were testis-specific, with (*) indicating significance as above. Figure concept and male reproductive tract outline in (A) adapted from Dean et al. (2009); the preleptotene cell was traced from Endo et al. (2015), and all other cell images were adapted from Larson et al. (2018).