SPATIAL GENETIC STRUCTURE OF COMMON WALNUT (JUGLANS REGIA L.) IN CENTRAL ASIA

Sampled and analyzed walnut populations were geographically isolated by arid lowland, mountain slopes and highland steppes. Clustering approaches produced convergent results, dividing the samples into four main genetic clusters. Most genetic cluster were confined to particular mountain ranges, showing distinct phylogeographic structure. The construction of synthetic overlay maps using GIS showed coincidence between genetic clusters of walnut samples and potential barriers to gene flow that likely promoted the isolation and local adaptation of walnut demes. The spatial arrangement of genetic clusters of Eurasian walnuts indicated that ancient trade routes facilitated walnut dispersal and gene flow over enormous distances.