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 diffe...多倍化（Polyploidy）是真核生物演化进程中的关键影响因子，在被子植物（angiosperms）中分布尤为广泛，且多倍化常与杂交协同作用，进而产生异源多倍体（allopolyploids）。学界借助分子系统发育技术已探明众多异源多倍体的起源，但尽管异源多倍化在推动异源多倍体与其亲本物种产生分化上发挥着关键作用，目前对异源多倍化所引发的基因组与染色体层面的效应仍知之甚少。本研究通过多种质体（plastid）与细胞核序列标记，明确了一类美国雏菊类群中四倍体（tetraploids）与六倍体（hexaploids）的起源，由此得以对比分析多倍体与其二倍体祖先的基因组动态特征。所有多倍体物种均为异源多倍体。在四个二倍体基因库中，异源多倍化的发生倾向在系统发育分布上并不均衡，少数物种似乎更易参与该过程，但其背后的深层成因仍未明晰。多倍体基因组的特征表现为差异……