Previous records of chromosome numbers for species belonging to the genus Teucrium (Lamiaceae) are summarized here. The frequency of different chromosome base numbers and the karyological patterns available, including frequency of cytotype occurrence in the genus, are also discussed. In addition, chromosome numbers of seven populations belonging to three species growing in Iran, namely T. stocksianum (2n = 2x = 26), T. polium (2n = 2x = 26) and T. orientale (2n = 2x=26), are presented here. The present work aimed to explain the evolutionary trend in Teucrium on the basis of base chromosome number and comparing index of chromosome number heterogeneity (ICNH) between different sections. Our results about the relationships between chromosome numbers, geographical distribution and ploidy levels indicate that both aneuploidy and polyploidy have played an important role in the speciation processes in Teucrium.
