Is genome downsizing associated with diversification in polyploid lineages ofVeronica?

Abstract

The study of genome size evolution in a phylogenetic context in related polyploid and diploid lineages can help us to understand the advantages and disadvantages of genome size changes and their effect on diversification. Here, we contribute 199 new DNA sequences and a nearly threefold increase in genome size estimates in polyploid and diploid Veronica (Plantaginaceae) (to 128 species, c. 30% of the genus) to provide a comprehensive baseline to explore the effect of genome size changes. We reconstructed internal transcribed spacer (ITS) and trnL‐trnL‐trnF phylogenetic trees and performed phylogenetic generalized least squares (PGLS), ancestral character state reconstruction, molecular dating and diversification analyses. Veronica 1C‐values range from 0.26 to 3.19 pg. Life history is significantly correlated with 1C‐value, whereas ploidy and chromosome number are strongly correlated with both 1C‐ and 1Cx‐values. The estimated ancestral Veronica 1Cx‐value is 0.65 pg, with significant genome downsizing in the polyploid Southern Hemisphere subgenus Pseudoveronica and two Northern Hemisphere subgenera, and significant genome upsizing in two diploid subgenera. These genomic downsizing events are accompanied by increased diversification rates, but a ‘core shift’ was only detected in the rate of subgenus Pseudoveronica. Polyploidy is important in the evolution of the genus, and a link between genome downsizing and polyploid diversification and species radiations is hypothesized. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178, 243–266.

Chromosome numbers and DNA content in some species of Mecardonia (Gratiolae, Plantaginaceae)

“…However, there are still many families and genera being neglected, including Mecardonia , for which the present study is the first analysis of genome size for the genus. The estimates 2C- and 1C-values calculated for the species in this study are within ranges of variation found in Angiosperms and Plantaginaceae (Leitch and Bennett 2004, Meudt et al 2015). Based on the available genome size data, Mecardonia falls into the categories “very small” genomes (2C = <2.8 pg) to “small” genomes (2C = <7.0 pg) according to values reported by Leitch et al (1998) and Soltis et al (2004).…”

“…Recently, Meudt et al (2015) established a relationship between the genome downsizing with diversification in polyploid lineages of Veronica (Plantaginaceae), but they do not know how general this pattern might be or what causes it. Several hypotheses have been proposed to explain this relationship.…”

“…In Mecardonia species there are no reported measurements of DNA content, but genome size variation has been explored in some genera of Plantaginaceae. DNA C-values are currently available for 204 species belonging to 18 genera of this family, including Callitriche Linnaeus, 1753, Penstemon Schmidel, 1762, Plantago Linnaeus, 1753 and Veronica Linnaeus, 1753 with a range of variation of 0.32–4,.63 pg (Albach and Greilhuber 2004, Broderick et al 2011, Bennett and Leitch 2012, Wong and Murray 2012, Prančl et al 2014, Meudt et al 2015). Herein we used flow cytometry to estimate the nuclear DNA content in five species of Mecardonia for the first time.…”

Polyphyletic Alyssum cuneifolium (Brassicaceae) revisited: Morphological and genome size differentiation of recently recognized allopatric taxa

“…The prevalent trend towards genome downsizing correlated with increasing ploidy level in polyploid series of closely related species (or within species) has been repeatedly confirmed in many plant genera, most recently, for example, in Aloe L. (Rao et al, ), Avena L. (Yan et al, ), Calligonum L. (Gouja et al, ), Chrysanthemum L. (Luo et al, ), Festuca L. (Ezquerro‐López et al, ), Fragaria L. (Nosrati, ), Knautia L. (Frajman et al, ), Sesleria Scop. (Lazarević et al, ) and Veronica L. (Meudt et al, ). Considering this general trend, the opposite patterns observed in the Alyssum species under study could be attributed to the fact that they are not each others' closest relatives (Zozomová‐Lihová et al, ; Španiel et al, ); however, there are also other possible explanations.…”

Typifications and taxonomic notes for Veronica subgen. Pseudolysimachium (Plantaginaceae) based on material from the Hungarian Natural History Museum Budapest (BP)

“…Pseudolysimachium. The subgenus is characterized by a number of morphological characters ) and dated to have originated between approximately 12 my (stem age) and 3 my ago (crown age) by Meudt et al (2015). It is considered to be the fastest radiating subgenus of the genus in the Northern Hemisphere (Meudt et al 2015).…”