Abstract
BackgroundSexual dimorphism in ecologically important traits is widespread, yet the differences in the genomic architecture between the two sexes are largely unexplored. We employed a genome-wide multilocus approach to examine the sexual differences in population subdivision, natural selection and linkage disequilibrium (LD) in a wild Siberian jay (Perisoreus infaustus) population, using genotypes at a total of 107 autosomal and Z-chromosomal microsatellites.ResultsMean observed heterozygosity was significantly higher in females (HO = 0.567) than in males (HO = 0.532), and autosomal markers (HO = 0.561) were more variable than Z-chromosomal markers (HO = 0.512). Genetic differentiation (FST = 0.002, P < 0.05) between the two sexes was low but significant and males were on average significantly more genetically related to each other than females. Genomescan analyses revealed that 3 out of 101 (3%) autosomal loci were under directional selection, while 4 out of 6 (67%) Z-chromosomal markers were indicated to be under balancing selection. This suggests a significantly greater but contrasting selection force on the Z-chromosome in comparison to autosomes, which is consistent with an overall significantly (P < 0.05) lower FSTvalue for Z-chromosomal (-0.014, 95% CI: -0.025 - -0.011) than for the autosomal loci (0.003, 95% CI: 0.001 - 0.004). Analysis of syntenic marker pairs revealed high levels of LD in both sexes but significantly (P < 0.05) lower levels of LD in the females both on autosomes and Z-chromosome, probably due to the higher rate of dispersal and the higher recombination rates on autosomes, as well as the pseudoautosomal markers. In both sexes LD decayed rapidly with genetic distance in a similar fashion on autosomes, while a more rapid decay of LD in Z-chromosome was detected in females than in males.ConclusionWe conclude that there are many clear differences in genomic architecture between the sexes studied here which can be at least partly understood in the light of higher dispersal rate of females as compared to males and the unusual structure of the Z-chromosome of the species.
Highlights
Sexual dimorphism in ecologically important traits is widespread, yet the differences in the genomic architecture between the two sexes are largely unexplored
Sexual dimorphism in genomic architecture - including the extent of linkage disequilibrium (LD) - is expected to occur both for selective and demographic reasons
Using sex-specific linkage maps, we investigated the decay of LD with genetic distance in the sexes
Summary
Sexual dimorphism in ecologically important traits is widespread, yet the differences in the genomic architecture between the two sexes are largely unexplored. We employed a genome-wide multilocus approach to examine the sexual differences in population subdivision, natural selection and linkage disequilibrium (LD) in a wild Siberian jay (Perisoreus infaustus) population, using genotypes at a total of 107 autosomal and Z-chromosomal microsatellites. Large differences in the forces of evolution - mutation, recombination, selection, gene flow, and genetic drift are known to occur between males and females Understanding the relative importance of evolutionary forces that shape patterns of sex-specific genomic dimorphism is essential to our understanding of. Sexual dimorphism in genomic architecture - including the extent of linkage disequilibrium (LD) - is expected to occur both for selective and demographic reasons. A multilocus approach as used e.g. in Drosophila, maize and humans (e.g. [14,15]) is a powerful way to disentangle the effects of sex-related evolutionary forces on genomic variation
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