Morphological study of populations of the genus Dracocephalum to determine the limits of D. kotschyi complex in Iran

Dracocephalum L. (Lamiaceae) contains ۱۰ species in the Flora of Iran. A morphometric analysis based on morphological data was conducted to determine the circumscription of the species complex of D. kotschyi. Morphological characteristics of ۱۳ populations of D. kotschyi, three populations of D. oligadenium, two populations of D. ghahremanii and D. lindbergii, and one population of D. moldavica and D. subcapitatum were examined in ۳۵ quantitative and qualitative traits. To identify the most variable traits among the studied species, factor analysis was performed, revealing that, traits such as the ratio of leaf length to width at the basal leaves, apical and middle leaf shape, presence of hairs on leaves and bracts, and corolla color had the greatest positive impact on species separation. By using Ward's method for cluster analysis, three main clusters were identified in the resulting dendrogram. The first cluster included D. moldavica, which was clearly separated from other species. The second cluster comprised various populations of D. kotschyi (a۲) and its closely related species, namely, D. subcapitatum and D. ghahremanii (b۲). In this cluster, the distinction of D. ghahremanii from other populations of D. kotschyi and its proximity to D. subcapitatum was confirmed. The third cluster included populations of D. lindbergii (a۳) and populations of D. oligadenium, which according to the cluster analysis of morphological traits, were distinguished from D. kotschyi and recognized as an independent species i.e., D. oligadenium. The number of species in Dracocephalum in Iran has therefore, increased to ۱۱.

Keywords:

dendrogram , numerical taxonomy , population , Lamiaceae , medicinal plant