Polyploidy and new chromosome counts in Pseudognaphalium Kirp. (Compositae: Gnaphalieae)

© 2018, © 2018 Dipartimento di Biologia, Università di Firenze. Pseudognaphalium Kirp. (Compositae: Gnaphalieae) comprises approximately 90 species and it has a worldwide but fragmented distribution. This study provides a total of 20 chromosome counts, nine of which are the first report for a species, and the rest are confirmation of previous reports. With the addition of these data to the previously published reports, the chromosome numbers for a total of 32 species of the genus Pseudognaphalium are now available. Considering all chromosome data available at present, c.22% of the species are diploids and c.78% are polyploids, mainly tetraploids. African and Asian species are predominantly diploid whereas the vast majority of the American species are tetraploid, suggesting that polyploidy played a key role in the colonization of the American continent by the genus Pseudognaphalium.