Abstract
Chromosome numbers and heterochromatin banding pattern variability have been shown to be useful for taxonomic and evolutionary studies of different plant taxa. Bignonieae is the largest tribe of Bignoniaceae, composed mostly by woody climber species whose taxonomies are quite complicated. We reviewed and added new data concerning chromosome numbers in Bignonieae and performed the first analyses of heterochromatin banding patterns in that tribe based on the fluorochromes chromomycin A3 (CMA) and 4'-6-diamidino-2-phenylindole (DAPI). We confirmed the predominant diploid number 2n = 40, as well as variations reported in the literature (dysploidy in Mansoa [2n = 38] and polyploidy in Dolichandra ungis-cati [2n = 80] and Pyrostegia venusta [2n = 80]). We also found a new cytotype for the genus Anemopaegma (Anemopaegma citrinum, 2n = 60) and provide the first chromosome counts for five species (Adenocalymma divaricatum, Amphilophium scabriusculum, Fridericia limae, F. subverticillata, and Xylophragma myrianthum). Heterochromatin analyses revealed only GC-rich regions, with six different arrangements of those bands. The A-type (one large and distal telomeric band) were the most common, although the presence and combinations of the other types appear to be the most promising for taxonomic studies.
Highlights
Bignonieae is the largest tribe in Bignoniaceae, comprising more than 393 species in 21 genera (Lohmann and Ulloa 2017)
We considered here the heterochromatin patterns of 24 species of Bignonieae based on the fluorochromes chromomycin A3 (CMA) and 4’-6-diamidino-2-phenylindole (DAPI), as well as variations in the chromosome numbers of 62 species of the tribe
The heterochromatin banding patterns of 24 species belonging to 12 genera of lianas and shrubs were examined
Summary
Bignonieae is the largest tribe in Bignoniaceae, comprising more than 393 species in 21 genera (Lohmann and Ulloa 2017). Molecular phylogenetic studies have shown that previous generic system did not reflect evolutionary relationships between lineages within the tribe. Forty-seven genera were previously recognized, but only 21 lineages were retrieved (Lohmann 2006). Among those lineages, six reflected genera that kept their previous circumscriptions (Anemopaegma, Lundia, Martinella, Pyrostegia, Styzophyllum, and Tynanthus). The remaining species were combined into 15 genera with broader circumscriptions that are recognizable by previously unused synapomorphies (Lohmann and Taylor 2014). Despite this new and robust system, some of the genera whose circumscriptions were altered are morphologically very close, and it remains difficult to distinguish them (Lohmann and Taylor 2014)
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