Karyomorphological Analysis and Genome Size Variation of Sixteen <i>Callicarpa</i> Taxa in China

Abstract

Information on chromosomes and estimation of genome size could be applied to study the evolution and classification of a genus. In our study, the conventional pressing method was applied to prepare microscope slides for counting the chromosomes, and the chromosome numbers of all surveyed species were 2n=32, 34, 36, 38. The first-time determination of chromosome counts for 12 taxa and karyotypes for 16 taxa in Callicarpa were conducted. It exposed all the species with a higher ratio of m chromosomes and a lower ratio of sm chromosomes, and only C. macrophylla contained st chromosome pair. The minor differences between the karyotypes of all species revealed that the karyotype diversity of this genus evolved from a tiny variation of chromosome structure. Meanwhile, the genome size of 23 samples from 16 taxa of Callicarpa has been estimated by flow cytometry. The genome size ranged from 0.96 pg (C. pedunculata) to 1.26 pg (C. nudiflora), averaged out at 1.12 pg, and the variation of genome sizes was fine among the investigated species. Hence, it could also be referred from the viewpoints of cytology that Callicarpa was a group in Lamiaceae that evolved earlier and independently.