Morphology and genetic diversity of Marrubium cuneatum Russell and M. parviflorum Fisch. & C.A. Mey

Marrubium parviflorum Fisch. & C.A. Mey. and Marrubium cuneatum Russell, are naturally distributed in various parts of Iran. It is difficult to clearly identify these species, because of their morphological similarities. Therefore, in the current study, we investigated the morphological characteristics and genetic diversity among various populations of these species in the country to find more variable traits and compare their genetic structure. In total, we evaluated 16 populations of these species, with up to ten replications per each population. For morphology, we studied the quantitative and qualitative characteristics of both reproductive and vegetative organs. For molecular investigations, the nuclear DNA was extracted using modified CTAB method and amplified using twelve ISSR molecular primers. Data were analyzed using SPSS, PAST, GenAlex, STRUCTURE, and Geno–Dive. Results indicated that in both species, most of the quantitative and qualitative morphological characteristics varied among and within the populations. Parameters of genetic diversity and polymorphism differed among the populations of both species. According to AMOVA test, the great proportion of significant genetic difference in M. parviflorum belonged to within populations, which was supported by a high rate of gene flow, a weak population genetic differentiation and clustering analyses. While, the reverse conditions were registered in M. cuneatum populations. According to Nei’s genetic distance and structure analysis, populations of M. parviflorum and M. cuneatum were clustered into seven and five genetics groups, respectively. However, the populations of both species were mixed together in morphological and ISSR dendrograms, which revealed similarity between them. It seems that the occurrence of ancestral gene flow or recent speciation were responsible for these similarities.