one or two. QTLs are analyzed using Qst. Qst looks at the relatedness of the traits in focus. In the case of QTLs, clines are analyzed by Qst. A cline (biology) is a change in allele frequency across a geographical distance. This change in allele frequency causes a series of intermediate varying phenotypes that when associated with certain environmental conditions can indicate selection. This selection causes local adaptation, but high gene flow is still expected to be present along the cline. For example, barn owls in Europe exhibit a cline in reference to their plumage coloration. Their feathers range in coloration from white to reddish-brown across the geological range of the southwest to the northeast. This study sought to find if this phenotypic variation was due to selection by calculating the Qst values across the owl populations. Because high gene flow was still anticipated along this cline, selection was only expected to act upon the QTLs that incur locally adaptive phenotypic traits. This can be determined by comparing the Qst values to Fst (fixation index) values. If both of these values are similar and Fst is based on neutral markers then it can be assumed that the QTLs were based on neutral markers (markers not under selection or locally adapted) as well. However, in the case of the barn owls the Qst value was much higher than the Fst value. This means that high gene flow was present allowing the neutral markers to be similar, indicated by the low Fst value. But, local adaptation due to selection was present as well, in the form of varying plumage coloration since the Qst value was high, indicating differences in these non-neutral loci. In other words, this cline of plumage coloration has some sort of adaptive value to the birds. Fixation indices Fixation indices are used when determining the level of genetic differentiation between sub-populations within a total population. FST is the script used to represent this index when using the formula: In this equation, HT represents the expected heterozygosity of the total population and HS is the expected heterozygosity of a sub-populations. Both measures of heterozygosity are measured at one loci. In the equation, heterozygosity values expected from the total population are compared to observed heterozygosity values of the sub-populations within this total population. Larger FST values imply that the level of genetic differentiation between sub-populations within a total population is more