Regions of high differentiation--worth a check.

B. Boursot and K. Belkhir in this issue of Genome Research point to an ascertainment bias in my use of SNPs to identify regions of high differentiation between a pair of house mouse subspecies. Here, I discuss additional points to consider and argue that the ultimate test for such regions should be an independent confirmation using unrelated samples. I provide evidence that regions of high differentiation as identified from laboratory strains and potentially biased SNP markers can be confirmed and therefore are worth a deeper investigation.