Commentary: evidence that sexually antagonistic male coloration factors are clustered in a rarely recombining region near the guppy male-determining locus

A recently published genome sequence of a YY guppy male supports long-standing suggestions about the Y-linked region of this fish-that it includes both the male-determining locus and also male coloration factors that have sexually antagonistic effects. Selection against effects of these factors in females is expected to maintain associations with the male-determining locus, and to select for closer linkage in the region, and might lead to suppressed recombination and "evolutionary strata". The new finding that two sequenced Y chromosomes differ specifically in this region suggests that these represent two different Y haplotypes carrying different coloration factors that have been maintained for long enough that their sequences have become differentiated. As theory predicts, such a genome region will show complex peaks and troughs of sequence diversity, and it may be very difficult to locate the individual male-determining and male coloration loci, even when both types of factors have been maintained long-term by frequency-dependent balancing selection.