Polyploidization and Genome Size Evolution in Australian Billy Buttons (Craspedia, Asteraceae: Gnaphalieae)

Abstract

Premise of research. The Australian members of the genus Craspedia (Asteraceae: Gnaphalieae) are known to contain polyploids, but only a very limited number of chromosome counts are available, and a systematic overview of ploidy levels and genome sizes is lacking. In the present study, we aimed to document chromosome number variation across the genus in Australia, test whether polyploids occur more often in alpine than in lowland environments, and test whether there is a proportional increase in genome size with polyploidy that would enable the use of flow cytometry as a proxy for chromosome counts in future studies.Methodology. We used flow cytometry to measure genome sizes (2C values) of 59 individual plants and obtained 45 chromosome counts from root tip squashes.Pivotal results. We found polyploidy to be common and documented intraspecific ploidy variation in several species, indicating multiple independent origins of polyploidy within the genus. Polyploidy was not more prevalent in high-elevation spe...