Genome sequencing of fish from a natural population of the guppy, Poecilia reticulata, for studying sex chromosome evolution

This sequencing is part of an integrated programme of molecular genetic studies of sex chromosome evolution, and specifically, to use the guppy (Poecilia reticulata) to test the sexual antagonism (SA) hypothesis that suppressed recombination between X and Y chromosomes evolves to remove or mitigate inter-sexual conflict when genes with SA polymorphisms are closely linked to a sex-determining gene, i.e. located in the partially sex-linked (pseudo-autosomal) region, or PAR, of sex chromosome pairs. The guppy is a model system for studies of SA since male coloration phenotypes make males attractive to females, but also make fish conspicuous to predators (with females receiving no compensating benefit). Our study employs dense DNA-based markers to identify fully and partially sex linked sequences and study linkage disequilibrium patterns in the chromosome carrying these regions. The markers will subsequently be used in genetic mapping to determine the genomic locations of coloration genes, even in the presence of male-specific expression of some of these phenotypes. The sequences will also be used in population genetic analyses to test whether recombination rates between the male-determining region and genetic markers in the PAR differ between natural populations with low and high predation rates, and molecular evolutionary analyses to estimate the age of the guppy sex chromosome system.