Chromosomal evolution in the genus Thottea Rottb. (Aristolochiaceae) from the Western Ghats, India

Cytotaxonomic investigations were carried out on eight species of the medicinally important genus Thottea from the Western Ghats, India. Chromosome numbers are reported for the first time in seven endemic Thottea spp. The meiotic and mitotic chromosome numbers are discussed in taxonomic and phylogenetic contexts. Uniformity in chromosome numbers in all the species except T. barberi reveals the genetic resemblance between them. Thottea barberi seems unique with n = 14 and 2n = 28, which could be the result of an ascending aneuploidy from n = 13, i.e. n = 13 to 14 by duplication of one chromosome. Remaining seven species with n = 13 and 2n = 26 might be derived by the union of gametes with n = 6 and n = 7, since the basic chromosome number in the family Aristolochiaceae ranges from 4 to 7, 12 and 13. The resultant diploid species by interaction with the environment may lead to different morphotypes. © 2013 Archana Sharma Foundation of Calcutta.