Independent stratum formation on the avian sex chromosomes reveals inter-chromosomal gene conversion and predominance of purifying selection on the W chromosome

Alison E Wright, Peter W Harrison, Stephen H Montgomery, Marie A Pointer, Judith E Mank

Research output: Contribution to journalArticle (Academic Journal)peer-review

Abstract

We used a comparative approach spanning three species and 90 million years to study the evolutionary history of the avian sex chromosomes. Using whole transcriptomes, we assembled the largest cross-species dataset of W-linked coding content to date. Our results show that recombination suppression in large portions of the avian sex chromosomes has evolved independently, and that long-term sex chromosome divergence is consistent with repeated and independent inversions spreading progressively to restrict recombination. In contrast, over short-term periods we observe heterogeneous and locus-specific divergence. We also uncover four instances of gene conversion between both highly diverged and recently evolved gametologs, suggesting a complex mosaic of recombination suppression across the sex chromosomes. Lastly, evidence from 16 gametologs reveal that the W chromosome is evolving with a significant contribution of purifying selection, consistent with previous findings that W-linked genes play an important role in encoding sex-specific fitness.

Original languageEnglish
Pages (from-to)3281-95
Number of pages15
JournalEvolution
Volume68
Issue number11
DOIs
Publication statusPublished - Nov 2014

Bibliographical note

© 2014 The Authors. Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

Keywords

  • Animals
  • Biological Evolution
  • Birds/classification
  • Female
  • Gene Conversion
  • Male
  • Sex Chromosomes

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