A taxonomic revision of Tanacetum polycephalum (Asteraceae, Anthemideae) species complex from Iran

Tanacetum polycephalum is one of the most problematic species of T. sect. Xanthoglossa. In this study, forty-three quantitative and qualitative morphological characters were measured for thirty-four different populations of T. polycephalum and four populations of its allies, e. g. T. canescens, T. tabrisianum, and T. elbursense. The data matrix was analyzed by cluster and principal co-ordinate analysis using the PAST software. The results indicated that the T. polycephalum complex contains three distinct groups, which could be recognized as segregated taxa. Herein, T. azerbaidjanicum comb. stat. nov. and T. argyrophyllum are known as separate species. A diagnostic identification key and notes about habitats, phytogeography, chromosome data, and distributions are presented.