Karyotypic features and cluster analysis of <i>Callicarpa</i> (Lamiaceae) from China

Conventional chromosome preparation methods were used to observe and analyze the karyotypes of six Callicarpa species. We also analyzed the evolutionary trends and performed parametric clustering based on karyotypic features for 22 Callicarpa species. This research aimed to complement the chromosomal information for Callicarpa, and provide a cytological basis for further exploration of phylogenetic relationships in this genus. The results showed that (1) six Callicarpa species were diploid with chromosome number 2n=2x=34, 36, and 38. The karyotypes consisted of median centromeric chromosomes (m) and submedian centromeric chromosomes (sm), and the karyotypes were 1B, 2A, and 2B, which suggested relatively primitive types. (2) C. integerrima, C. rubella, and C. macrophylla were inferred to be the more advanced species, with C. integerrima having the most advanced karyotype according to Stebbins’ theory of karyotype evolutionary trends in plants. (3) Clustering of karyotypic parameters classified 22 species of Callicarpa into four major groups. In addition, we discussed the clustering results in comparison with the traditional classification system of Callicarpa, which showed partial agreement between the karyotypic clustering and the traditional classification.