article published yes Andrea Mrnjavac author 353FAC84-AE61-11E9-8BFC-00D3E5697425 Kseniia Khudiakova author 4E6DC800-AE37-11E9-AC72-31CAE56974250000-0002-6246-1465 Nicholas H Barton author 4880FE40-F248-11E8-B48F-1D18A9856A870000-0002-8548-5240 Beatriz Vicoso author 49E1C5C6-F248-11E8-B48F-1D18A9856A870000-0002-4579-8306 GradSch department BeVi department Optimal Transport and Stochastic Dynamics project Prevalence and Influence of Sexual Antagonism on Genome Evolution project Differentiated X chromosomes are expected to have higher rates of adaptive divergence than autosomes, if new beneficial mutations are recessive (the “faster-X effect”), largely because these mutations are immediately exposed to selection in males. The evolution of X chromosomes after they stop recombining in males, but before they become hemizygous, has not been well explored theoretically. We use the diffusion approximation to infer substitution rates of beneficial and deleterious mutations under such a scenario. Our results show that selection is less efficient on diploid X loci than on autosomal and hemizygous X loci under a wide range of parameters. This “slower-X” effect is stronger for genes affecting primarily (or only) male fitness, and for sexually antagonistic genes. These unusual dynamics suggest that some of the peculiar features of X chromosomes, such as the differential accumulation of genes with sex-specific functions, may start arising earlier than previously appreciated. https://research-explorer.ista.ac.at/download/12521/14068/2023_EvLetters_Mrnjavac.pdf application/pdfno Oxford University Press2023 eng GeneticsEcologyEvolutionBehavior and Systematics 2056-3744 37065438 00102169220000110.1093/evlett/qrac004 71 https://research-explorer.ista.ac.at/record/18531 Mrnjavac, Andrea, et al. “Slower-X: Reduced Efficiency of Selection in the Early Stages of X Chromosome Evolution.” <i>Evolution Letters</i>, vol. 7, no. 1, qrac004, Oxford University Press, 2023, doi:<a href="https://doi.org/10.1093/evlett/qrac004">10.1093/evlett/qrac004</a>. A. Mrnjavac, K. Khudiakova, N.H. Barton, B. Vicoso, Evolution Letters 7 (2023). Mrnjavac, Andrea, Kseniia Khudiakova, Nicholas H Barton, and Beatriz Vicoso. “Slower-X: Reduced Efficiency of Selection in the Early Stages of X Chromosome Evolution.” <i>Evolution Letters</i>. Oxford University Press, 2023. <a href="https://doi.org/10.1093/evlett/qrac004">https://doi.org/10.1093/evlett/qrac004</a>. Mrnjavac, A., Khudiakova, K., Barton, N. H., &#38; Vicoso, B. (2023). Slower-X: Reduced efficiency of selection in the early stages of X chromosome evolution. <i>Evolution Letters</i>. Oxford University Press. <a href="https://doi.org/10.1093/evlett/qrac004">https://doi.org/10.1093/evlett/qrac004</a> Mrnjavac A, Khudiakova K, Barton NH, Vicoso B. 2023. Slower-X: Reduced efficiency of selection in the early stages of X chromosome evolution. Evolution Letters. 7(1), qrac004. Mrnjavac A, Khudiakova K, Barton NH, Vicoso B. Slower-X: Reduced efficiency of selection in the early stages of X chromosome evolution. <i>Evolution Letters</i>. 2023;7(1). doi:<a href="https://doi.org/10.1093/evlett/qrac004">10.1093/evlett/qrac004</a> A. Mrnjavac, K. Khudiakova, N. H. Barton, and B. Vicoso, “Slower-X: Reduced efficiency of selection in the early stages of X chromosome evolution,” <i>Evolution Letters</i>, vol. 7, no. 1. Oxford University Press, 2023. 125212023-02-06T13:59:12Z2026-08-06T22:31:02Z