Javascript is not activated in your browser. This website needs javascript activated to work properly.
You are here

Patterns of molecular evolution of an avian neo-sex chromosome.

  • Irene Pala
  • Dennis Hasselquist
  • Staffan Bensch
  • Bengt Hansson
Publishing year: 2012
Language: English
Pages: 3741-3754
Publication/Series: Molecular biology and evolution
Volume: 29
Issue: 12
Document type: Journal article
Publisher: Oxford University Press

Abstract english

Newer parts of sex chromosomes, neo-sex chromosomes, offer unique possibilities for studying gene degeneration and sequence evolution in response to loss of recombination and population size decrease. We have recently described a neo-sex chromosome system in Sylvioidea passerines that has resulted from a fusion between the first half (10 Mb) of chromosome 4a and the ancestral sex chromosomes. In the present study, we report the results of molecular analyses of neo-Z and neo-W gametologues and intronic parts of neo-Z and autosomal genes on the second half of chromosome 4a in three species within different Sylvioidea lineages (Acrocephalidea, Timaliidae and Alaudidae). In line with hypotheses of neo-sex chromosome evolution, we observe (i) lower genetic diversity of neo-Z genes comparatively to autosomal genes, (ii) moderate synonymous and weak non-synonymous sequence divergence between neo-Z and the neo-W gametologues and (iii) lower GC content on neo-W than on neo-Z gametologues. Phylogenetic reconstruction of eight neo-Z and neo-W gametologues suggests that recombination continued after the split of Alaudidae from the rest of the Sylvioidea lineages (i.e. after approximately 42.2 MYA) and with some exceptions also after the split of Acrocephalidea and Timaliidae (i.e. after approximately 39.4 36 MYA). The Sylvioidea neo-sex chromosome shares classical evolutionary features with the ancestral sex chromosomes, but as expected from its more recent origin shows weaker divergence between gametologues.


  • Biological Sciences
  • recombination cessation
  • ZW gametolog divergence
  • avian neo-sex chromosome


  • Sex chromosome evolution and sex-biased expression
  • Centre for Animal Movement Research
  • Molecular Ecology and Evolution Lab
  • ISSN: 0737-4038
Dennis Hasselquist
E-mail: dennis [dot] hasselquist [at] biol [dot] lu [dot] se



+46 46 222 37 08



Research group


Doctoral students and postdocs

Research fellows


PhD Students, main supervisor

PhD Students, assistant supervisor


Interview about my research in the Swedish podcast "Forskarn & jag"