Unveiling the numbers: current state of knowledge of chromosome number counts in big plant genera

Overall, the proportion of species with at least one chromosome count is low (14%) with temporal trend revealing an unequivocal decline in counts acquisition after the 90s, coinciding with advances in DNA amplification and sequencing and molecular phylogenetics. In addition, logistic regressions confirmed our expectations that the proportion of species with chromosome count per genus is lower for genera with a tropical distribution, being primarily trees or exhibiting specialised pollination to complete sexual reproduction. Contrary to our expectations, taxonomic uncertainty is strongly positively associated with the availability of chromosome counts per genus. We argue that a higher taxonomic uncertainty has promoted more sampling to aid the circumscription of plant species, highlighting the crucial role of chromosome variation in identifying genomic traits that have supported the diversification of big plant genera.