Extensive analysis of native and non-native Centaurea solstitialis L. populations across the world shows no traces of polyploidization.

Ramona-Elena Irimia,Özkan Eren,Gastón J Sotes,Andreia Jorge,Christopher J Lortie,João Loureiro,Daniel Montesinos,José L Hierro,Lohengrin A Cavieres,Kristine French

doi:10.7717/peerj.3531

Abstract

Centaurea solstitialis L. (yellow starthistle, Asteraceae) is a Eurasian native plant introduced as an exotic into North and South America, and Australia, where it is regarded as a noxious invasive. Changes in ploidy level have been found to be responsible for numerous plant biological invasions, as they are involved in trait shifts critical to invasive success, like increased growth rate and biomass, longer life-span, or polycarpy. C. solstitialis had been reported to be diploid (2n = 2x = 16 chromosomes), however, actual data are scarce and sometimes contradictory. We determined for the first time the absolute nuclear DNA content by flow cytometry and estimated ploidy level in 52 natural populations of C. solstitialis across its native and non-native ranges, around the world. All the C. solstitialis populations screened were found to be homogeneously diploid (average 2C value of 1.72 pg, SD = ±0.06 pg), with no significant variation in DNA content between invasive and non-invasive genotypes. We did not find any meaningful difference among the extensive number of native and non-native C. solstitialis populations sampled around the globe, indicating that the species invasive success is not due to changes in genome size or ploidy level.

Highlights

Changes in ploidy level have been reported to be important for the invasive success of some plants species (Te Beest et al, 2011), by altering morphological, physiological and ecological parameters which can confer hybrid vigor, stress resistance, competitive advantages, or increased phenotypic plasticity, like in the case of the North American tetraploids of Centaurea stoebe L. (Hahn, Buckley & Müller-Schärer, 2012)
At least three individuals from every population were used to estimate genome size (Table S2), in different days, to account for the variation generated by the flow cytometer
We found no traces of polyploidization events in the C. solstitialis populations investigated and geographic differences in genome size were negligible

Summary

Introduction

Changes in ploidy level have been reported to be important for the invasive success of some plants species (Te Beest et al, 2011), by altering morphological, physiological and ecological parameters which can confer hybrid vigor, stress resistance, competitive advantages, or increased phenotypic plasticity, like in the case of the North American tetraploids of Centaurea stoebe L. (Hahn, Buckley & Müller-Schärer, 2012). Changes in ploidy level have been reported to be important for the invasive success of some plants species (Te Beest et al, 2011), by altering morphological, physiological and ecological parameters which can confer hybrid vigor, stress resistance, competitive advantages, or increased phenotypic plasticity, like in the case of the North American tetraploids of Centaurea stoebe L. (reed canary grass, Poaceae) in the USA underwent a quick and significant reduction in genome size compared to the native European genotype, which was correlated with some advantageous phenotypic effects and enhanced aggressiveness (Lavergne, Muenke & Molofsky, 2010). For many invasive species, ploidy levels and genome size are unknown or have not been thoroughly investigated

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