Synopsis of Cytological Studies on Didymocarpoideae (Gesneriaceae) under New Classification System

Abstract:

Based on molecular phylogenetic evidences, the classification of Gesneriaceae was dramatically changed in recent years. Especially, many genera in the Old Word have been systematically rearranged. However, cytological data of Gesneriaceae have not been re-examined. The cytological data of the Old Word Gesneriads, obtained from WebCyte database, Chromosome Counts Database and related literature, were summarized under the new taxonomic framework of Gesneriaceae. The results showed that the cytological data in Didymocarpoideae was still insufficient. Chromosome number of less than 25% species in this subfamily were reported, and that for many genera have never been reported. Some newly revised genera show uniform somatic chromosome number. However, some genera, such as Henckelia and Didymocarpus, have great variation in chromosome number. Based on these available cytological data, several comments and suggestions on the evolution of chromosome and its influence to species diversification in this family were proposed. It was speculated that both polyploidy and dysploidy of chromosome possibly play important roles to the diversification of some genera. Future works based on new chromosome painting techniques, convinced phylogenetic evidences, and genomics are warranted in studying chromosome evolution of this group.

Key words:Gesneriaceae;Didymocarpoideae;Chromosome number;Chromosome evolution