The genomic landscape of species divergence in Ficedula flycatchers

Hans Ellegren*, Linnéa Smeds, Reto Burri, Pall I. Olason, Niclas Backström, Takeshi Kawakami, Axel Künstner, Hannu Mäkinen, Krystyna Nadachowska-Brzyska, Anna Qvarnström, Severin Uebbing, Jochen B.W. Wolf

*Corresponding author for this work
366 Citations (Scopus)


Unravelling the genomic landscape of divergence between lineages is key to understanding speciation. The naturally hybridizing collared flycatcher and pied flycatcher are important avian speciation models that show pre-as well as postzygotic isolation. We sequenced and assembled the 1.1-Gb flycatcher genome, physically mapped the assembly to chromosomes using a low-density linkage map and re-sequenced population samples of each species. Here we show that the genomic landscape of species differentiation is highly heterogeneous with approximately 50 'divergence islands' showing up to 50-fold higher sequence divergence than the genomic background. These non-randomly distributed islands, with between one and three regions of elevated divergence per chromosome irrespective of chromosome size, are characterized by reduced levels of nucleotide diversity, skewed allele-frequency spectra, elevated levels of linkage disequilibrium and reduced proportions of shared polymorphisms in both species, indicative of parallel episodes of selection. Proximity of divergence peaks to genomic regions resistant to sequence assembly, potentially including centromeres and telomeres, indicate that complex repeat structures may drive species divergence. A much higher background level of species divergence of the Z chromosome, and a lower proportion of shared polymorphisms, indicate that sex chromosomes and autosomes are at different stages of speciation. This study provides a roadmap to the emerging field of speciation genomics.

Original languageEnglish
Issue number7426
Pages (from-to)756-760
Number of pages5
Publication statusPublished - 29.11.2012

Research Areas and Centers

  • Academic Focus: Center for Infection and Inflammation Research (ZIEL)


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