Karyotypes of some endemic species of Dicliptera (Acanthaceae) from India reveal variation in chromosome number

Dicliptera (Acanthaceae) is a pantropical genus that comprises more than 200 species. Karyotypes of eight species that are endemic to Peninsular India were studied. Mitotic metaphases revealed four chromosome counts, 2n=26, 52, 56, and 58. Chromosome counts of 2n=26 for D. beddomei, D. nasikensis, and D. srisailamica, 2n=56 for D. foetida and D. ghatica and 2n=58 for D. baphica were observed for the first time. The total haploid chromosome length (THL) ranged from 45.77 µm (D. cuneata) to 108.6 µm (D. foetida). Karyotypes were symmetric as all chromosomes had median (m) region centromeres. Considerable variation in chromosome number indicates the existence of more than one base number and the role of polyploidy in the evolution of the genus. Dispersion index (DI) showed a direct correlation with the coefficient of variation of chromosome length (CVCL) and differentiated Dicliptera karyotypes. Species with higher CVCL values (D. baphica, D. beddomei, D. cuneata, and D. foetida) had higher DI values (ranging from 3.22–4.86) whereas D. ghatica, D. leonotis, D. nasikensis, and D. srisailamica had lower DI values (ranging from 2.58–3.14). Principal component analysis based on eight parameters, namely somatic count (2n), THL, CVCL, CVCI, DI, mean centromeric asymmetry (MCA), mean chromosome length (MCL), and ratio of longest to shortest chromosome of a complement (R) grouped the species in three clusters. Cluster I comprised D. srisailamica, D. nasikensis, and D. beddomei. D. cuneata, D. ghatica, and D. leonotis formed Cluster II whereas Cluster III had D. baphica and D. foetida. Our studies suggest that an in-depth cytogenetic investigation including meiotic studies can shed light on the chromosomal evolution and speciation in this genus.