Data from: The promiscuous and the chaste: frequent allopolyploid speciation and its genomic consequences in American daisies (Melampodium sect. Melampodium; Asteraceae)

Polyploidy, an important factor in eukaryotic evolution, is especially
abundant in angiosperms, where it often acts in concert with hybridization
to produce allopolyploids. The application of molecular phylogenetic
techniques has identified the origins of numerous allopolyploids, but
little is known on genomic and chromosomal consequences of
allopolyploidization, despite their important role in conferring
divergence of allopolyploids from their parental species. Here, using
several plastid and nuclear sequence markers, we clarify the origin of
tetra- and hexaploids in a group of American daisies, allowing
characterization of genome dynamics in polyploids compared to their
diploid ancestors. All polyploid species are allopolyploids. Among the
four diploid gene pools, the propensity for allopolyploidization is
unevenly distributed phylogenetically with a few species apparently more
prone to participate, but the underlying causes remain unclear. Polyploid
genomes are characterized by differential loss of ribosomal DNA loci (5S
and 35S rDNA), known hotspots of chromosomal evolution, but show genome
size additivity, suggesting limited changes beyond those affecting rDNA
loci or the presence of processes counterbalancing genome reduction.
Patterns of rDNA sequence conversion and provenance of the lost loci are
highly idiosyncratic and differ even between allopolyploids of identical
parentage, indicating that allopolyploids deriving from the same
lower-ploid parental species can follow different evolutionary
trajectories.