Genome size variation among and within Ophiopogoneae species by flow cytometric analysis

Genome size variation in a taxonomic group reflects evolutionary processes. DNA contents of Ophiopogoneae (40 populations of 31 species) were estimated by flow cytometry. Ploidy levels of Ophiopogon (ten species), Liriope (two species), and Peliosanthes (three species) were determined based on the DNA contents. The genus Peliosanthes showed significant larger genome sizes than Ophiopogon (P < 0.01), and Ophiopogon also significant larger than Liriope (P < 0.05). Intraspecific variation in genome size was mainly chromosome difference. The ITS sequence phylogeny splitted Ophiopogon into two clades, clade I comprising sect. Ophiopogon with diploids and tetraploids, and clade II including transitional species and sects. Ophiopogon and Peliosanthoides with diploids. The trend seemed to increase in genome size from Ophiopogon sect. Peliosanthoides (13.45 pg) to Ophiopogon sect. Ophiopogon (14.27 pg). Polyploidization may be evolutionary direction of Ophiopogon. Our results also suggested that the ‘increase’ hypothesis for genome size evolutionary may hold true in the genus Ophiopogon.