Genetic Substructuring of the populations from the area of South-Eastern Europe

Despite of an overall low differentiation in human population, especially in Europe area, varial local factors such as geographic, cultural or continuing reproductive isolation can enhance genetic discontinuity. As some of the few persisting isolates among contemporary South- Eastern European (SE European) human groups, isolated Croatian islands are among the most suitable models for analyses of human population differentiation. In this study the data obtained by means of the analysis of 9 autosomal STR loci of microsatelite DNA in Croatian islands and Slovenian populations were integrated with the published data from other Croatian islands and wide SE European region. The sample was defined hierarchically in two levels: the first one included 7 Croatian islands sub-populations and the second one included 10 neighboring SE European populations. We detected lower genetic differentiation at the higher lever of grouping of SE European populations (K = 3) than at the level of sub-populations of Croatia islands (K = 6). Results obtained with the clustering algorithm implemented by STRUCTURE illustrate that a relatively small number of loci is sufficient to reveal consistent structure when differentiation is high. These findings are supportive of the notion that specific genetic features of isolated Croatian islands have been shaped through the constant interaction of population genetic characteristic and wide spectrum of environmental influences through history. Due to strong influence of genetic drift, small isolates rapidly acquire very distinctive alleles frequencies.