Conservation of synteny between guppy and Xiphophorus genomes.

The guppy and fish in the genus Xiphophorus have both been important model systems for the study of natural and sexual selection for over 50 years. Whereas the guppy is unique in the degree to which the environmental variables shaping phenotypic variation are known, Xiphophorus has the advantage that genomic resources have been developed due to the utility of this taxon for the study of melanoma. If linkage maps for the guppy and Xiphophorus are similar, genomic resources developed in Xiphophorus will be useful in the guppy. The authors used an F2 mapping cross of divergent populations of the guppy to construct partial female and male genetic linkage maps incorporating microsatellite markers derived from Xiphophorus mapping efforts. Flanking regions for a sample of microsatellites occurring in maps for both taxa were sequenced in the guppy and compared to published sequences from Xiphophorus. This confirmed that these loci were homologous and estimated the divergence in neutral nuclear DNA to be 0.21 substitutions per site. The female map comprises 16 linked markers on six linkage groups, and the male map comprises 24 markers on nine linkage groups. Linkage relationships among loci homologous in the guppy and Xiphophorus primarily show conservation of genetic architecture between species, but several major changes were detected.