Cytogenetic diversity in the polyploid complex Linum suffruticosum s.l. (Linaceae)

Abstract

Abstract Polyploidy plays a significant role in the evolution and diversification of flowering plants. In several polyploid complexes, high morphological variability and plasticity coupled with cytogenetic diversity make it difficult to disentangle their evolutionary history. The main goal of this study was to gain insights into the role of whole genome duplications as one of the factors shaping the evolution of flowering plants. Linum suffruticosum s.l. has been described as a polyploid complex, with high morphological variability, but nothing is known about current cytogeographical patterns. We investigated cytotype diversity and distribution patterns in 151 populations covering most of the distribution range, in the Iberian Peninsula, south-eastern France, north-western Italy and Morocco, using flow cytometric analyses complemented with chromosome counts. A high cytogenetic diversity was found with five major cytotypes being detected (diploids, tetraploids, hexaploids, octoploids and decaploids) and with new ploidy levels being reported for the first time. The different ploidies were distributed parapatrically, with geographical structure and several contact zones. Most of the populations comprised one cytotype, but a few mixed-ploidy populations were observed. Our results suggest that whole genome duplications are one of the key mechanisms, alone or together with hybridization, governing the diversification of L. suffruticosum s.l. Genome size and/or chromosome counts might be useful tools for identifying specimens of L. suffruticosum s.l. Also, geographical overlap and high cytogenetic diversity suggest multiple origins of the polyploids. The diversity observed here has been mostly neglected to date and should be accounted when studying the biosystematics of this complex.