Identification of sex-linked SNP markers in wild populations of
monomorphic birds
Abstract
Single-nucleotide polymorphism (SNP) analyses are a powerful tool for
population genetics, pedigree reconstruction and phenotypic trait
mapping. SNPs could also be useful for sexing individuals in species
with reduced sexual dimorphism, yet this possibility remains poorly
explored. Here, we develop a novel protocol for molecular sexing of
birds based on the detection of unique Z- and W-linked SNP markers. Our
method is based on the identification of two unique loci, one in each
sexual chromosome. Individuals are considered males when they are
heterozygotic for the Z-linked SNP and females when they are homozygote
for the Z-linked SNP and have the W-linked SNP. We validated the method
in the Jackdaw (Corvus monedula), a species whose reduced sexual
dimorphism makes it difficult to sex individuals in the wild. We
assessed the reliability of the method with 36 individuals of known sex,
and found that their sex was correctly assigned in 100% of cases. The
sex-linked markers also proved to be widely applicable to discriminate
males and females from a sample of 927 genotyped individuals of
different maturity stages with an accuracy of 99.5%. Given that SNP
markers are increasingly used in quantitative genetic analyses of wild
populations, the approach we propose has a great potential to be
integrated into broader genetic research programmes without the need of
additional sexing techniques.