## 3 Results and Discussion
### Population Differentiation and Structure  
Due to the anemophilic pollen dispersal mechanism, an increasing degree of differentiation correlated with geographical distance was anticipated. However, the results showed a low degree of genetic differentiation among populations and no evidence of geographic structuring across the sampled distribution of the species. No differentiation was observed between populations P7 Prelog and P3 Varazdin, as well as between P8 Novo Virje and P3 Varazdin, and P8 Novo Virje and P5 Krizevci (\(F_{ST}=0.00\)). The highest value of genetic differentiation was observed between populations P1 Ozalj, sampled from the southwestern part and P7 Prelog, sampled in the northern parts of the sampled area, the two populations most distant from each other. Only one pairwise \(F_{ST}\) between populations P1 Ozalj and P7 Prelog was significant (\(0.01<p<0.05\) after 10,000 permutations) (Table S2). The data obtained suggest pollen-mediated connectivity which reduces \(F_{ST}\) through increased pollen flow. The high gene flow between populations of \(H\). _Iupulus_ occurs at sufficient levels to minimize genetic difference. The low degree of genetic divergence among the studied populations can also be explained by a common genetic pool and the absence of differential selection pressure. High levels of gene flow allow for the maintenance of high genetic diversity and are expected to maintain genetic consistency among populations, reducing genetic divergence among populations [85]. Low gene flow rates are thought to produce genetic differentiation through genetic drift and selection [86]. Most of the total genetic diversity resulted from differences between individuals within populations (98.64%), indicating weak differentiation among populations (\(q_{ST}=0.014\)), although still significant after 10,000 permutations (\(p<0.0001\)), following the Analysis of Molecular Variance (AMOVA) approach. This is consistent with predictions that cross-pollinating species with wind-dispersed pollen mechanism retain most of the genetic variation within populations [87], as the distribution of genetic variability within and among populations greatly depends on the breeding system in particular plant populations [88]. The results of the factorial correspondence analysis (PCA) revealed various aspects of microsatellite diversity in hop, indicating some degree of differentiation among populations. Figure 2 presents the projection of individuals and population barycenters onto the plane defined by the first two axes of the FCA. The first two axes accounted for 19.44 and 17.37% of the total inertia, respectively. The first axes separated most of the hop individuals from the southwestern population P1 Ozalj from the northern populations (P3 Varazdin,P4 Kalnik and P7 Prelog). The second axes separated the northernmost populations P6 Ludberg and the northeastern population P8 Novo Virje from the southwestern population P1 Ozalj and the southeastern population P2 Rugvica. Some individuals were drawn far from the barycenter of the original population, suggests the admixed origin of populations. Using Bayesian model-based clustering as implemented in STRUCTURE, without prior information on the populations to which the individuals belong (i.e., without LOCPRIOR option), the highest likelihood of the data (\(ln\) Pr(X 1 K) = \(-\)4453.20) and the highest average likelihood (\(-\)4454.19) were obtained at K = 1, indicating the absence of any population structure (Figure S1A). The highest \(\Delta\)K values were observed for K = 5 (3.65), followed by that of K = 4 (2.50). However, the analyses did not yield a biologically meaningful result for any value of K, as shown in Figure S2A. Between 97% (for K = 3) and 100% (for K = 2, K = 10, K = 11) of individuals would be considered \"mixed\" with membership probabilities of less than 75% for each cluster from K = 2 to K = 11 (Figure S2A).