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Polyploidy in the Conifer Genus Juniperus: An Unexpectedly High Rate
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International audience. Recent research suggests that the frequency of polyploidy may have beenunderestimated in gymnosperms. One notable example is in the conifer genus Juniperus,where there are already a few reports of polyploids although data are still missing for mostspecies. In this study, we evaluated the extent of polyploidy in Juniperus by conductingthe first comprehensive screen across nearly all of the genus. Genome size data fromfresh material, together with chromosome counts, were used to demonstrate thatgenome sizes estimated from dried material could be used as reliable proxies to uncoverthe extent of ploidy diversity across the genus. Our analysis revealed that 16 Juniperustaxa were polyploid, with tetraploids and one hexaploid being reported. Furthermore, byanalyzing the genome size and chromosome data within a phylogenetic framework weprovide the first evidence of possible lineage-specific polyploidizations within the genus.Genome downsizing following polyploidization is moderate, suggesting limited genomerestructuring. This study highlights the importance of polyploidy in Juniperus, making itthe first conifer genus and only the second genus in gymnosperms where polyploidy isfrequent. In this sense, Juniperus represents an interesting model for investigating thegenomic and ecological consequences of polyploidy in conifers.
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