High genetic diversity within and low differentiation among Juniperus excelsa M. Bieb. populations: Molecular markers reveal their genetic structure patterns

J. excelsa M. Bieb forms about 82% of the total juniper forests in Turkey. A total of 456 plant samples belonging to 19 J. excelsa populations were collected to determine the genetic variation of J. excelsa and compare their genetic diversity among populations via simple-sequence repeat (SSR) and intron targeted amplified polymorphism (ITAP) markers. Seven SSR and 132 ITAP loci were polymorphic. The percentage of polymorphism for ITAP loci at the population level ranged from 31.34 to 55.97. Average values of expected heterozygosity, observed heterozygosity, Shannon's information index, Fis, Fst and Nm for SSR loci were 0.616, 0.512, 1.54, 0.124, 0.043, and 5.513, respectively. Genetic diversity values of ITAP loci were lower than those of SSR loci. Gst and Nm values for ITAP loci were 0.225 and 1.728, respectively. Pair-wise genetic distances varied between 0.023 and 0.292 for SSR loci, 0.010 and 0.110 for ITAP loci. The majority of the genetic variations originated from intra-population level (98% for SSRs, 80% for ITAPs). Mantel test results showed that there was no statistically significant correlation between pair-wise geographical and genetic distances. It was indicated that the populations had similiar structure pattern. It was seen that J. excelsa populations maintained their high genetic diversity. Additionally, genetic differentiations among the populations were low. No indication of genetic adverse effect related to habitat fragmentation was determined in the populations. In conclusion, it can be said that this situation is an advantage in terms of implementing conservation strategies for this species. The authorities in the Turkish Ministry of Forestry should plan some conservation studies in order to maintain the existing genetic diversity of this species.