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Genomic architecture of hybrid male sterility in a species without sex chromosomes (Tigriopus californicus, Copepoda: Harpacticoida).

Kevin C OlsenThiago G LimaFelipe S BarretoRonald S Burton
Published in: Genome biology and evolution (2023)
Sterility among hybrids is one of the most prevalent forms of reproductive isolation delineating species boundaries and is expressed disproportionately in heterogametic XY males. While hybrid male sterility (HMS) due to the 'large X effect' is a well-recognized mechanism of reproductive isolation, it is less clear how HMS manifests in species that lack heteromorphic sex chromosomes. We evaluated differences in allele frequencies at approximately 460,000 SNPs between fertile and sterile F2 interpopulation male hybrids to characterize the genomic architecture of HMS in a species without sex chromosomes (Tigriopus californicus). We tested associations between HMS and mitochondrial-nuclear and/or nuclear-nuclear signatures of incompatibility. Genomic regions associated with HMS were concentrated on a single chromosome with the same primary 2 Mbp region identified in one pair of reciprocal crosses. Gene Ontology analysis revealed that annotations associated with spermatogenesis were the most overrepresented within the implicated region, with 9 protein-coding genes connected with this process found in the QTL of chromosome 2. Our results indicate that a narrow genomic region was associated with the sterility of male hybrids in T. californicus and suggest that incompatibilities among select nuclear loci may replace the large X effect when sex chromosomes are absent.
Keyphrases
  • copy number
  • genome wide
  • dna methylation
  • genetic diversity
  • transcription factor
  • small molecule
  • genome wide identification
  • protein protein
  • genome wide association study
  • genome wide association