Genome size dynamics in tribe Gilliesieae (Amaryllidaceae, subfamily Allioideae) in the context of polyploidy and unusual incidence of Robertsonian translocations

This study focuses on tribe Gilliesieae (Amaryllidaceae, Allioideae), which stand out because of their karyotype diversity, constituting a textbook example of Robertsonian translocations (RTs), in which chromosomes fuse or break at the centromere. Polyploidy (i.e. whole genome duplication, WGD) is also common in the tribe, hence making Gilliesieae particularly suitable for investigating two major processes of genome evolution in an integrated way. Our phylogenetic reconstruction supported a two subtribe classification, Gilliesiinae and Leucocoryninae, the latter taxonomically validated in this paper. Leucocoryninae are composed of three well-supported lineages, corresponding to the genera Leucocoryne + Latace, blue-flowered (typical) Ipheion + Tristagma and Nothoscordum (including yellow-flowered Ipheion = Beauverdia). Analysis of the chromosome data in Leucocoryninae indicates that WGDs have resulted in an almost proportional genome size (GS) increase in Leucocoryne, in contrast to the reduction in monoploid GS in polyploid Nothoscordum. Likewise, contrasting patterns of GS dynamics and extraordinary karyotype diversity have been recovered in Ipheion, Tristagma and Nothoscordum, clearly illustrating the impact of RTs in shaping genome evolution in these plants.