Molecular cytogenetics of Dictyoloma vandellianum A. Juss. and the ancestral karyotype of Rutaceae

Abstract

Determination of the chromosome base number of a taxon is fundamental to understanding karyotypic variation and its implications for the evolution of that group. This usually requires careful evaluation of cytological literature and robust phylogenetic support. The base number for the family Rutaceae (x = 9 or x = 18) has long been the subject of debate. Here, we analyzed the banding pattern, rDNA sites, and genome size of Dictyoloma vandellianum, subfamily Cneoroideae, the sister group of the remaining Rutaceae, and revised critical points about the chromosome base number of the family. We found that this species has n = 9, which differs from the n = 18 possessed by other cytologically known Cneoroideae species. Thus, n = 9 occurs in the main clades of Rutaceae and is the most probable base number of the family. The hypothesis of x = 18 as the base number is no longer sustainable, although n = 18 is very common in Rutaceae. Moreover, the fluorescent banding pattern and the relatively large genome size (1C = 1.3 pg) of D. vandellianum suggest that its chromosomal organization is highly divergent from Aurantieae, the only large Rutaceae clade where species with n = 9 are greatly dominant.

Biological and Medicinal Properties of Natural Chromones and Chromanones

“…The Rutaceae is a highly diversified plant family comprising 150–162 genera and 1500–2096 species . Currently, only two subfamilies of Rutaceae are recognized, Rutoideae and Cneoroideae, the latter comprising only eight genera including Dictyoloma.…”