Achene micromorphology in Tanacetum (Asteraceae-Anthemideae) and its taxonomic and phylogenetic implications

•Achene micromorphology is useful for segregating of sections in Tanacetum.•Coroniform and unilateral pappus are the main types of achene.•Complete ring-like symmetric carpopodium is the common type.

Achene morphology of 37 taxa of Tanacetum, Ajania semnanensis, and Artemisia paradoxa were investigated using light- and scanning electron microscopy to evaluate the diagnostic value of such characters in infrageneric classification and to provide additional evidence on the delimitation of taxa. In this study, 26 quantitative and qualitative characteristics were examined using multivariate analysis. Cluster analysis and principal component analysis of the data showed that achene characters have significant value for separation of species from one another and support delimitation at the sectional level. The results revealed that the genus Tanacetum is separated into two main groups having either a coroniform or unilateral pappus. The congruency of micromorphological and molecular studies is discussed and evolutionary trends of some micromorphological traits are evaluated.