Fine structure of gene frequency landscapes in domestic cat: the Old and New Worlds compared

The dependence of variance of coat gene frequencies on geographic distance was studied in stray domestic cat populations by means of analysis of variance (ANOVA) and variance ratio test (F-test) with the data set containing 333 samples. The procedure included the stepwise estimation of variances within square pieces of territory of gradually increasing size performed separately for the Old and New Worlds. It is revealed that beginning with 200-300 km-size of square side, for the most loci studied, these distance-controlled variances are significantly less in the New World, thus indicating a smoother gene frequency landscape. In both worlds, the tb and t alleles show significantly higher variances than the other mutant alleles. The mean allele frequencies in the New World are significantly higher than in the western European area, from where colonization took place for alleles that constitute a "luxury" gene group (O, d, l, W) presumably formed by human preference. The results support in general the historical/immigration hypothesis, i.e., that domestic cat colonization of the New World proceeded by rapid population expansion without a great gene frequency change (bottleneck-like effect). A modification is suggested for the model: a biased colonization sample (a founder effect) in regards to O, d, l, and W alleles.