Data from: Multi-speed genome diploidization and diversification after an ancient allopolyploidization

Hybridization and genome doubling (allopolyploidy) have led to evolutionary novelties as well as to the origin of new clades and species. Despite the importance of allopolyploidization, the dynamics of post-polyploid diploidization (PPD) at the genome level has been only sparsely studied. The Microlepidieae (MICR) is a crucifer tribe of 17 genera and c. 56 species endemic to Australia and New Zealand. Our phylogenetic and cytogenomic analyses revealed that MICR originated via an inter-tribal hybridization between ancestors of Crucihimalayeae (n = 8; maternal genome) and Smelowskieae (n = 7; paternal genome), both native to the Northern Hemisphere. The reconstructed ancestral allopolyploid genome (n = 15) originated probably in north-eastern Asia or western North America during the Late Miocene (c. 10.6 - 7 million years ago) and reached the Australian mainland via long-distance dispersal. In Australia, the allotetraploid genome diverged into at least three main subclades exhibiting different levels of PPD and diversity: 1.25-fold descending dysploidy (DD) of n = 15 → n = 12 (autopolyploidy → 24) in perennial Arabidella (3 species), 1.5-fold DD of n = 15 → n = 10 in the perennial Pachycladon (11 spp.), and 2.1 to 3.75-fold DD of n = 15 → n = 7- 4 in the largely annual crown group genera (42 spp. in 15 genera). These results are among the first to demonstrate multi-speed genome evolution in taxa descending from a common allopolyploid ancestor. It is suggested that clade-specific PPD can operate at different rates and efficacies, and can be tentatively linked to life histories and the extent of taxonomic diversity.杂交与基因组加倍（异源多倍化，allopolyploidy）不仅可催生演化新性状，更能促成新支系与物种的起源。尽管异源多倍化作用至关重要，但基因组层面的多倍体后二倍体化（post-polyploid diploidization，PPD）动力学机制迄今仍鲜有研究。微鳞芥族（Microlepidieae，MICR）是一类仅分布于澳大利亚与新西兰的十字花科族，包含17个属、约56个物种。本研究通过系统发育与细胞基因组学分析发现，该族起源于十字岩荠族（Crucihimalayeae，染色体基数n=8，母本基因组）与斯迈洛芥族（Smelowskieae，染色体基数n=7，父本基因组）的祖先类群之间的跨族杂交，这两个族均原产于北半球。重构得到的祖先异源多倍体基因组（n=15）可能形成于中新世晚期（约1060万至700万年前）的东北亚或北美西部，并通过长距离扩散抵达澳大利亚大陆。在澳大利亚境内，该异源四倍体基因组分化出至少三个主支系，各自呈现出不同程度的PPD与多样性：多年生类群阿拉伯芥属（Arabidella，3个物种）经历了1.25倍的下行非整倍体化（descending dysploidy，DD），即n=15→n=12（伴随同源多倍化（autopolyploidy）→染色体数变为24）；多年生类群厚柄芥属（Pachycladon，11个物种）经历了1.5倍的下行非整倍体化，即n=15→n=10；而绝大多数为一年生的冠群类群（crown group），包含15个属共计42个物种，经历了2.1至3.75倍的下行非整倍体化，即n=15→n=7至4。本研究结果是首批证实源自同一异源多倍体祖先的类群存在多速率基因组演化的案例之一。研究表明，支系特异性的PPD可在不同速率与效率下运作，且可初步与生活史类型及分类多样性程度建立关联。