---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
_id: '23121'
abstract:
- lang: eng
  text: 'A widespread observation in molecular evolution is that X-linked genes evolve
    faster—and often adapt faster—than autosomal genes. Three main ideas have been
    put forward to explain “faster-X” adaptation. The first is that new beneficial
    mutations are typically partially recessive with respect to fitness, leading to
    more efficient selection in hemizygous males. The second is that sex differences
    in recombination, or sex differences in variance in reproductive success, enhance
    the effective population size on the X chromosome relative to autosomes. Both
    ideas have limitations: the first conflicts with theories of dominance, in which
    beneficial mutations are proposed to be partially dominant, while the second only
    applies to some taxa. Here we tested a third, newly-proposed theory, in which
    mutations with large “scaled phenotypic effects” (i.e., large effects relative
    to the distance to a phenotypic optimum) experience more positive selection on
    the X. Specifically, we used three proxies for scaled phenotypic effects—amino-acid
    dissimilarity, amino-acid conservation, and gene age—and estimated X and autosomal
    rates of adaptation of nonsynonymous mutations across effect-size classes. We
    did this in three lineages with a well-documented faster-X: Drosophila melanogaster,
    Mus musculus, and Homo sapiens. As expected, we found that large-effect mutations
    were more likely to be under purifying selection and less likely to be under positive
    selection than small-effect mutations. However, contrary to the new theory, faster-X
    adaptation was not enriched among large-effect mutations. Overall, our results
    highlight an unresolved gap between patterns of sex chromosome evolution and theories
    of dominance for fitness.'
article_number: evag259
article_processing_charge: Yes
article_type: original
author:
- first_name: Filip
  full_name: Ruzicka, Filip
  id: 347955dd-57b0-11ee-9095-c28bdd368f4b
  last_name: Ruzicka
- first_name: Beatriz
  full_name: Vicoso, Beatriz
  id: 49E1C5C6-F248-11E8-B48F-1D18A9856A87
  last_name: Vicoso
  orcid: 0000-0002-4579-8306
biorxivid: 1
citation:
  ama: Ruzicka F, Vicoso B. Is faster-X adaptation due to large-effect mutations?
    An empirical test of a new theory. <i>Genome Biology and Evolution</i>. 2026.
    doi:<a href="https://doi.org/10.1093/gbe/evag259">10.1093/gbe/evag259</a>
  apa: Ruzicka, F., &#38; Vicoso, B. (2026). Is faster-X adaptation due to large-effect
    mutations? An empirical test of a new theory. <i>Genome Biology and Evolution</i>.
    Oxford University Press. <a href="https://doi.org/10.1093/gbe/evag259">https://doi.org/10.1093/gbe/evag259</a>
  chicago: Ruzicka, Filip, and Beatriz Vicoso. “Is Faster-X Adaptation Due to Large-Effect
    Mutations? An Empirical Test of a New Theory.” <i>Genome Biology and Evolution</i>.
    Oxford University Press, 2026. <a href="https://doi.org/10.1093/gbe/evag259">https://doi.org/10.1093/gbe/evag259</a>.
  ieee: F. Ruzicka and B. Vicoso, “Is faster-X adaptation due to large-effect mutations?
    An empirical test of a new theory,” <i>Genome Biology and Evolution</i>. Oxford
    University Press, 2026.
  ista: Ruzicka F, Vicoso B. 2026. Is faster-X adaptation due to large-effect mutations?
    An empirical test of a new theory. Genome Biology and Evolution., evag259.
  mla: Ruzicka, Filip, and Beatriz Vicoso. “Is Faster-X Adaptation Due to Large-Effect
    Mutations? An Empirical Test of a New Theory.” <i>Genome Biology and Evolution</i>,
    evag259, Oxford University Press, 2026, doi:<a href="https://doi.org/10.1093/gbe/evag259">10.1093/gbe/evag259</a>.
  short: F. Ruzicka, B. Vicoso, Genome Biology and Evolution (2026).
corr_author: '1'
date_created: 2026-10-12T13:56:46Z
date_published: 2026-10-10T00:00:00Z
date_updated: 2026-10-14T08:17:09Z
day: '10'
ddc:
- '570'
department:
- _id: BeVi
doi: 10.1093/gbe/evag259
external_id:
  biorxivid:
  - 10.64898/2026.02.06.704462
fulldoi: https://doi.org/10.1093/gbe/evag259
has_accepted_license: '1'
keyword:
- evolutionary biology
- population genetics
- sex chromosomes
- adaptation
- genetic divergence
- McDonald-Kreitman test
- Fisher’s geometric model
language:
- iso: eng
license: https://creativecommons.org/licenses/by-nc/4.0/
main_file_link:
- open_access: '1'
  url: https://doi.org/10.1093/gbe/evag259
month: '10'
oa: 1
oa_version: Published Version
publication: Genome Biology and Evolution
publication_identifier:
  eissn:
  - 1759-6653
publication_status: epub_ahead
publisher: Oxford University Press
quality_controlled: '1'
scopus_import: '1'
status: public
title: Is faster-X adaptation due to large-effect mutations? An empirical test of
  a new theory
tmp:
  image: /images/cc_by_nc.png
  legal_code_url: https://creativecommons.org/licenses/by-nc/4.0/legalcode
  name: Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
  short: CC BY-NC (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
year: '2026'
...