Zataria multiflora is the only known species of the genus Zataria, which usually grows on dry and mountainous areas in the southwest, south and southeast of the Iranian plateau. Excessive harvesting, unfavorable climatic conditions and uncontrolled grazing have endangered its survival in native habitats. Therefore, identifying habitats and investigating morphological diversity are necessary to protect their populations. Between 2018 and 2019, the growth areas of this species were identified in different provinces of Iran and 15 populations in five provinces were selected to evaluate morphological diversity. Twenty-one morphological traits were analyzed by different methods. The number of inflorescences per plant, dry weight, the number of flowers per inflorescences, and fresh weight (coefficient of variation of 93.76, 73.08, 71.01, and 64.25%, respectively) were the main morphological traits with the highest variation among populations. Phenotypic correlation analysis showed a significant correlation among leaf dimensions, biomass parameters and reproductive traits. Cluster analysis, divided the 15 populations into two independent clusters. Thirteen populations with rather low amounts of morphological traits were grouped in the first cluster. In addition, two populations including Khonj and Juyom populations were placed in the second cluster that was characterized by higher values of important morphological traits in breeding programs of medicinal plants. Finally, in the present study it was observed that, high morphological variations in Z. multiflora populations from different parts of Iran that may be attributed to their different ecological, geographical origin and genetic factors.
