Genetic diversity and population structure of diverse Iranian Nepeta L. taxa

In the present study, we utilized ISSR molecular markers to investigate infraspecific and infrageneric genetic variations in 34 populations from 25 Nepeta L. taxa. We used the CTAB protocol for DNA extraction. PCR was performed using 20 ISSR primers, and 12 of which produced scorable bands. The genetic diversity and polymorphism analyses showed high genetic variation among the taxa and their populations. The Analysis of Molecular Variance revealed significant genetic variation (P ≤ 0.001), which its great part belonged to among taxa variation. These findings were supported by the considerable amounts of genetic differentiation (GST) and total genetic variation in the pooled species (HT) that revealed the high genetic divergence of the studied taxa. Furthermore, the reticulation network of gene flow, a small number of gen flow index (Nm), and the mean difference within each species (HS) indicated a reduced level of gene flow among the taxa. We detected high genetic diversity among the populations of the same species, which revealed high infraspecific diversity. The haplotype network (TCS) demonstrated genetic difference at similar loci among each population’s individuals due to mutations on a scaffold of genetic relationships. According to STRUCTURE analysis and the neighbor-joining tree, 15 genotypes were detected among the studied taxa and their populations. The clustering pattern of these taxa and their populations did not agree with previous infrageneric classifications of Nepeta species in sections or groups. The occurrence of mutations and restricted gene flow create high infraspecific genetic divergence, which is reflected well in the infrageneric classification of Nepeta. Therefore, infraspecific variation should be considered in each taxonomic treatment of the genus.