PREMISE: Plant genome size ranges widely, providing many opportunities to examine how genome size variation affects plant form and function . We analyzed trends in chromosome number, genome size, and leaf traits for the woody angiosperm clade Viburnum to examine the evolutionary associations, functional implications, and possible drivers of genome size .
METHODS: Chromosome counts and genome size estimates were mapped onto a Viburnum phylogeny to infer the location and frequency of polyploidization events and trends in genome size evolution . Genome size was analyzed with leaf anatomical and physiological data to evaluate the influence of genome size on plant function .
RESULTS: We discovered nine independent polyploidization events, two reductions in base chromosome number, and substantial variation in genome size with a slight trend toward genome size reduction in polyploids . We did not find strong relationships between genome size and the functional and morphological traits that have been highlighted at broader phylogenetic scales .
CONCLUSIONS: Polyploidization events were sometimes associated with rapid radiations, demonstrating that polyploid lineages can be highly successful . Relationships between genome size and plant physiological function observed at broad phylogenetic scales may be largely irrelevant to the evolutionary dynamics of genome size at smaller scales . The view that plants readily tolerate changes in ploidy and genome size, and often do so, appears to apply to Viburnum.