We read with great interest the recent work in PNAS by Bergero et al. (1) describing differences in male and female recombination patterns on the guppy ( Poecilia reticulata ) sex chromosome. We fully agree that recombination in males is largely confined to the ends of the sex chromosome. Bergero et al. interpret these results to suggest that our previous findings of population-level variation in the degree of sex chromosome differentiation in this species (2) are incorrect. However, we suggest that their results are entirely consistent with our previous report, and that their interpretation presents a false controversy. Our population genomic results indicate that crossing over between the X and Y is rare across most of … [↵][1]1To whom correspondence may be addressed. Email: a.e.wright{at}sheffield.ac.uk. [1]: #xref-corresp-1-1