Genome Size and Cytomolecular Diversification in Two Species of the South African Endemic Genus Tulbaghia L. (allioideae, Amaryllidaceae)

•In spite of the morphological karyotype similarity among Tulbagia species, our data indicate that small chromosomal and genomic changes are actively acting on the karyotype differentiation of its species.•Both species had the Arabidopsis-type (T3AG3)n and the vertebrate-type (T2AG3)n telomeric motifs in all chromosome termini, as well as CMA+ bands colocalized with 35S rDNA sites, CMA+ bands colocalized with 5S rDNA sites, small CMA+ bands with any colocalization with rDNA and 5S rDNA sites neutrally stained with CMA.•Karyotypic features of Tulbaghia, such as chromosome size and morphology, genome size, number and distribution of rDNA sites, and telomeric DNA composition resemble karyotypes of the subfamilies Allioideae and Gilliesieae, reinforcing the relationship among the three tribes. On the other hand, colocalization of CMA+ bands with 5S rDNA sites, observed here in T. simmleri, has never been reported for other species of these subfamilies.