Genome Size Diversity in Lilium (Liliaceae) Is Correlated with Karyotype and Environmental Traits

Abstract

Genome size (GS) diversity is of fundamental biological importance. The occurrence of giant genomes in angiosperms is restricted to just a few lineages in the analyzed genome size of plant species so far. It is still an open question whether GS diversity is shaped by neutral or natural selection. The genus Lilium, with giant genomes, is phylogenetically and horticulturally important and is distributed throughout the northern hemisphere. GS diversity in Lilium and the underlying evolutionary mechanisms are poorly understood. We performed a comprehensive study involving phylogenetically independent analysis on 71 species to explore the diversity and evolution of GS and its correlation with karyological and environmental traits within Lilium (including Nomocharis). The strong phylogenetic signal detected for GS in the genus provides evidence consistent with that the repetitive DNA may be the primary contributors to the GS diversity, while the significant positive relationships detected between GS and the haploid chromosome length (HCL) provide insights into patterns of genome evolution. The relationships between GS and karyotypes indicate that ancestral karyotypes of Lilium are likely to have exhibited small genomes, low diversity in centromeric index (CVCI) values and relatively high relative variation in chromosome length (CVCL) values. Significant relationships identified between GS and annual temperature and between GS and annual precipitation suggest that adaptation to habitat strongly influences GS diversity. We conclude that GS in Lilium is shaped by both neutral (genetic drift) and adaptive evolution. These findings will have important consequences for understanding the evolution of giant plant genomes, and exploring the role of repetitive DNA fraction and chromosome changes in a plant group with large genomes and conservation of chromosome number.

Phylogenetic trends and environmental correlates of nuclear genome size variation in Helianthus sunflowers

“…Phylogenetic comparative analyses provide the most powerful approach for elucidating patterns of GS expansion and contraction in light of evolutionary relationships and for exploring the potential causes and consequences of such changes through correlational analyses of GS with environmental and biological variables. Such studies have been performed at multiple phylogenetic levels, from comparisons of diverse land plants (Beaulieu et al ., ,b; Knight & Beaulieu, ; Whitney et al ., ; Bainard et al ., ; Vesely et al ., ; Lomax et al ., ; Alonso et al ., ; Bromham et al ., ) to taxonomically more restricted analyses within plant families (Veleba et al ., ; Carta & Peruzzi, ; Ng et al ., ), and genera (Albach & Greilhuber, ; Grotkopp et al ., ; Jakob et al ., ; Gallagher et al ., ; Kang et al ., ; Meudt et al ., ; Baniaga et al ., ; Mandak et al ., ; Du et al ., ). Because of the highly dynamic nature of GS evolution and potential problems of representative sampling within groups for broader taxonomic comparisons, studies at lower taxonomic ranks – i.e.…”

“…Relationships between GS and environmental and/or climatic variables have been explored in several plant groups with comparisons drawn at various taxonomic levels (Knight & Ackerly, ; Grotkopp et al ., ; Vesely et al ., ; Diez et al ., ; Kang et al ., ; Carta & Peruzzi, ; Du et al ., ; Li et al ., ; Bilinski et al ., ; Lyu et al ., ). While findings have not been universally consistent (Knight et al ., ), multiple studies have suggested that environmental conditions ultimately may place constraints on the evolution of GS.…”

“…That life history strategies may exert selection on GS is further suggested by correlations of GS with environmental parameters such as altitude, latitude, temperature and precipitation (Knight & Ackerly, ; Grotkopp et al ., ; Knight et al ., ; Kang et al ., ; Du et al ., ; Bilinski et al ., ; Lyu et al ., ). Some of the most intriguing environmental correlates indicate that species with larger genomes tend to be excluded from more climatically extreme and/or temporally variable environments where growing seasons are shorter (Knight & Ackerly, ; Knight et al ., ).…”

Flow cytometry – a modern method for exploring genome size and nuclear DNA synthesis in horticultural and medicinal plant species

“…For example, Knight and Ackerly (2002) examined variation in GS for over 400 plant species in California in relation to the mean July maximum temperature, January minimum temperature, and annual precipitation, and concluded that species with small GS predominate in all environments, while those with large genomes occur at intermediate July maximum temperatures, and decline in frequency at both extremes of the July temperature gradient, and with decreasing annual precipitation. Another example are species of Lilium, possessing giant genomes, in which GS correlates negatively with annual temperatures and precipitation (Du et al, 2017).…”

Genome Size Unaffected by Variation in Morphological Traits, Temperature, and Precipitation in Turnip

“…Genome size (GS), being an indicator of evolutionary distance [1], is an important biodiversity trait [2] for molecular characterization of living organisms at a rapid pace. Many authors have proposed adaptive significance of GS variation [3][4][5][6][7][8]. Hence, GS is considered as proxy for understanding elementary biological processes at different spatial scales [9].…”