ASIP and freckles: Here there was an association between melanism and variation in ASIP: all nine jet-black melanic individuals, sampled from a single population in northern Georgia, were homozygous for a single bp substitution (G361T) leading to a Gly121Cys mutation, whereas all other colour group 2 individuals (n = 32) were heterozygous or homozygous for other alleles (Fisher’s exact test: P < 10− 10) (Table 1 and Additional file 3).