Abstract
Bignoniaceae is a diverse family composed of 840 species with Pantropical distribution. The chromosome number 2n = 40 is predominant in most species of the family, with n = 20 formerly being considered the haploid base number. We discuss here the haploid base number of Bignoniaceae and examine heterochromatin distributions revealed by CMA/DAPI fluorochromes in the Tabebuia alliance, as well as in some species of the Bignonieae, Tecomeae, and Jacarandeae tribes. When comparing the chromosome records and the phylogenies of Bignoniaceae it can be deduced that the base number of Bignoniaceae is probably n = 18, followed by an ascendant dysploidy (n = 18 → n = 20) in the most derived and diverse clades. The predominant heterochromatin banding patterns in the Tabebuia alliance were found to be two terminal CMA+ bands or two terminal and two proximal CMA+ bands. The banding pattern in the Tabebuia alliance clade was more variable than seen in Jacarandeae, but less variable than Bignonieae. Despite the intermediate level of variation observed, heterochromatin banding patterns offer a promising tool for distinguishing species, especially in the morphologically complex genus Handroanthus.
Highlights
Bignoniaceae is a Pantropical family composed mostly of trees and lianas, and includes 82 genera and 840 species (Fischer et al, 2004; Lohmann and Ulloa, 2016)
The main objective of this work was to describe the cytotaxonomic differences between related species of Bignoniaceae by examining their heterochromatin distributions, and discuss the haploid base number of the Bignoniaceae based on compilations of the chromosome numbers known for all lineages of the family
While banding patterns are still seldom-used in taxonomic studies, the results reported here support their utility in such analyses
Summary
Bignoniaceae is a Pantropical family composed mostly of trees and lianas, and includes 82 genera and 840 species (Fischer et al, 2004; Lohmann and Ulloa, 2016). Eight tribes are nested within the family: Bignonieae, Catalpeae, Coleeae, Crescentieae, Jacarandeae, Oroxyleae, Tecomeae, and Tourrettieae, plus the informal Crescentiina clade, that comprises the Neotropical and Palaeotropical subclades (Olmstead et al, 2009). While the morphological features of most tribes of Bignoniaceae are well-characterized, the Crescentiina clade and its subclades are well-sustained lineages, without clear morphological synapomorphies (Grose and Olmstead, 2007; Olmstead et al, 2009). The Crescentiina clade comprises two informal lineages: the exclusively Neotropical Tabebuia alliance and the Paleotropical clade with Asian and African genera (Olmstead et al, 2009). There is great morphological variability within the Tabebuia alliance, so that the delimitation of its species is often difficult
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