Abstract
BackgroundSex-specific DNA markers can serve as tools for molecular sex identification, as well as for population genetic inferences. We investigated the potential utility of a microsatellite marker located on sex chromosomes for molecular sexing of Fennoscandian nine-spined sticklebacks (Pungitius pungitius). In addition, we assessed the patterns of allelic differentiation between X and Y chromosomes across the populations to examine if the sex chromosomes had been highly differentiated prior to the postglacial recolonization of Fennoscandia.FindingsA clear and consistent sex difference in allele size distribution was observed at the Stn19 locus throughout the 15 populations investigated. Males were distinguishable by the presence of distinct male-specific alleles, which were lacking in all females. There was no indication of recombination between sex and the Stn19 locus in the 647 individuals tested. The degree of genetic differentiation between the X and Y chromosomes was much higher than that of interpopulation differentiation in the respective chromosomes.ConclusionsOur results indicate that the Stn19 locus can be used for molecular sex identification in Fennoscandian nine-spined sticklebacks. The consistent pattern of high allelic differentiation between the X and Y chromosomes in these populations suggests that the sex chromosomes were already highly differentiated prior to the postglacial recolonization of Fennoscandia.
Highlights
Sex-specific DNA markers can serve as tools for molecular sex identification, as well as for population genetic inferences
Our results indicate that the Stn19 locus can be used for molecular sex identification in Fennoscandian nine-spined sticklebacks
The consistent pattern of high allelic differentiation between the X and Y chromosomes in these populations suggests that the sex chromosomes were already highly differentiated prior to the postglacial recolonization of Fennoscandia
Summary
Sex-specific DNA markers can serve as tools for molecular sex identification, as well as for population genetic inferences. Even though many fish do not possess heteromorphic sex chromosomes, genetic sex determination has been found in a wide variety of fish species [1] This was initially demonstrated in species displaying sex-linked phenotypic traits such as skin pigmentation or coloration [2,3,4,5]. DNA markers tightly associated with phenotypic sex have been reported in several fish species [9,10,11,12,13] Such DNA markers can serve as simple and reliable diagnostic tools for sex identification of immature individuals
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