4.3 Article

Widespread genomic signatures of reproductive isolation and sex-specific selection in the Eastern Yellow Robin, Eopsaltria australis

Journal

G3-GENES GENOMES GENETICS
Volume 12, Issue 9, Pages -

Publisher

OXFORD UNIV PRESS INC
DOI: 10.1093/g3journal/jkac145

Keywords

speciation; hybrid zones; mitonuclear; Haldane's Rule; sex-specific selection; sex chromosomes; inversions

Funding

  1. Australian Research Council (Victorian Department of Sustainability and Environment) [DP180102359, LP0776322]
  2. Australian Research Council (Museum of Victoria) [DP180102359, LP0776322]
  3. Australian Research Council (Victorian Department of Primary Industries) [DP180102359, LP0776322]
  4. Australian Research Council (Parks Victoria) [DP180102359, LP0776322]
  5. Australian Research Council (North Central Catchment Management Authority) [DP180102359, LP0776322]
  6. Australian Research Council (Goulburn Broken Catchment Management Authority) [DP180102359, LP0776322]
  7. Monash School of Biological Sciences
  8. BirdLife Australia
  9. Holsworth Wildlife Research Endowment

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The Eastern Yellow Robin, a common passerine in Australia, exhibits divergence between its mitochondrial and nuclear genomes, potentially due to admixture and chromosomal inversion. Despite the absence of assortative mating, there is evidence of reproductive isolation between populations, with greater differentiation in females. This suggests that the species experiences postzygotic isolation, consistent with Haldane's Rule.
How new species evolve is one of the most fundamental questions in biology. Population divergence, which may lead to speciation, may be occurring in the Eastern Yellow Robin, a common passerine that lives along the eastern coast of Australia. This species is composed of 2 parapatric lineages that have highly divergent mitochondrial DNA; however, similar levels of divergence have not been observed in the nuclear genome. Here we re-examine the nuclear genomes of these mitolineages to test potential mechanisms underlying the discordance between nuclear and mitochondrial divergence. We find that nuclear admixture occurs in a narrow hybrid zone, although the majority of markers across the genome show evidence of reproductive isolation between populations of opposing mitolineages. There is an 8 MB section of a previously identified putative neo-sex chromosome that is highly diverged between allopatric but not parapatric populations, which may be the result of a chromosomal inversion. The neo-sex chromosomal nature of this region, as well as the geographic patterns in which it exhibits divergence, suggest it is unlikely to be contributing to reproductive isolation through mitonuclear incompatibilities as reported in earlier studies. In addition, there are sex differences in the number of markers that are differentiated between populations of opposite mitolineages, with greater differentiation occurring in females, which are heterozygous, than males. These results suggest that, despite the absence of previously observed assortative mating, mitolineages of Eastern Yellow Robin experience at least some postzygotic isolation from each other, in a pattern consistent with Haldane's Rule.

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