Network Analysis on Y Chromosome Haplogroups in Western Balkan Populations

The region of Western Balkans has been inhabited since the Paleolithic era and was the route of farming from the Middle East to Europe during the Neolithic era (7th millennium BC). In the present study, Y-STR data from worldwide populations have been used to construct median-joining networks. The study was performed using Whit Athey’s Haplogroup Predictor, Y Utility and Network 4 software packages to construct networks, perform clustering of closely related Y chromosomes and calculate time estimates between individual nodes. The results of the study imply that geographically close populations cluster together on both worldwide and European level. It was observed that an elevated number of study populations and individual haplogroups increases the possibility that individuals of different racial and ethnic background cluster within the same or neighboring clades of network. An example is the case of the Nigerian population clustering closely with the populations from the Western Balkans. Subsequent time estimates performed based on the mutation frequency between the ancestral node and its descendant nodes revealed that I2a is the oldest haplogroup in the major area of the Balkan Peninsula (estimated separation time from its ancestral state: 4858 years), followed by haplogroups E1b1b (4088 years) and R1a (3910 years). This study is based on data collected from a single database and, therefore, gives approximations of the relative time distance between the nodes. Our results are nonetheless in accordance with previously published papers investigating the frequency of Y haplogroups based on Y-SNP variant frequencies, indicating that Western Balkan countries are mainly represented by I2a subclade (average for six countries 35.93%), followed by the other two haplogroups (average for six countries 23.16% and 10.62% regarding R1a and E1b1b, respectively).