Insights into the dynamics of genome size and chromosome evolution in the early diverging angiosperm lineage Nymphaeales (water lilies)

Abstract

Nymphaeales are the most species-rich lineage of the earliest diverging angiosperms known as the ANA grade (Amborellales, Nymphaeales, Austrobaileyales), and they have received considerable attention from morphological, physiological, and ecological perspectives. Although phylogenetic relationships between these three lineages of angiosperms are mainly well resolved, insights at the whole genome level are still limited because of a dearth of information. To address this, genome sizes and chromosome numbers in 34 taxa, comprising 28 species were estimated and analysed together with previously published data to provide an overview of genome size and chromosome diversity in Nymphaeales. Overall, genome sizes were shown to vary 10-fold and chromosome numbers and ploidy levels ranged from 2n = 2x = 18 to 2n = 16x = ∼224. Distinct patterns of genome diversity were apparent, reflecting the differential incidence of polyploidy, changes in repetitive DNA content, and chromosome rearrangements within and between genera. Using model-based approaches, ancestral genome size and basic chromosome numbers were reconstructed to provide insights into the dynamics of genome size and chromosome number evolution. Finally, by combining additional data from Amborellales and Austrobaileyales, a comprehensive overview of genome sizes and chromosome numbers in these early diverging angiosperms is presented.

Genome size evolution: patterns, mechanisms, and methodological advances

“…Bainard and Villarreal (2013) give the first comprehensive survey of genome size variation in hornworts, a critical group in the land plant phylogeny suggested to be sister to extant tracheophytes. In addition, Pellicer et al (2013) provide genome size and chromosome counts for the Nymphaeales, an early diverging group of plants within the angiosperms. Bainard et al (2011a) furthered our understanding of fern and clubmoss genome size variation.…”

Evolutionary trends in Iridaceae: new cytogenetic findings from the New World

“…The nuclear DNA content, or genome size (GS or 2C), plays a role during species evolution and has become a valuable trait in biosystematics (Šmarda, Bureš & Horová, 2007;Bennett & Leitch, 2011;Pellicer et al, 2013Pellicer et al, , 2014. However, despite its importance, genome sizes have been estimated for only c. 1.8% of all angiosperm species (Bennett & Leitch, 2012).…”

Genome size in aquatic and wetland plants: fitting with the large genome constraint hypothesis with a few relevant exceptions

“…So, further research is needed to be definitely conclusive on the relationships between genome size and the important ecological and adaptive specificities of the aquatic habitat. (http://data.kew.org/cvalues; using prime estimate option) and Pellicer et al (2013). VS: very small, 2C ≤ 2.8 pg ; S: small, 2.8 < 2C ≤ 7 pg; I: intermediate, 7 < 2C < 28 pg; L: large, 28 ≤ 2C < 70 pg; VL: very large, 2C ≥ 70 pg.…”