The consequences of the Cretaceous-Paleogene (K-Pg) boundary (KPB) mass extinction for the evolution of plant diversity remain poorly understood, even though evolutionary turnover of plant lineages at the KPB is central to understanding assembly of the Cenozoic biota. The apparent concentration of whole genome duplication (WGD) events around the KPB may have played a role in survival and subsequent diversification of plant lineages. To gain new insights into the origins of Cenozoic biodiversity, we examine the origin and early evolution of the globally diverse legume family (Leguminosae or Fabaceae). Legumes are ecologically (co-)dominant across many vegetation types, and the fossil record suggests that they rose to such prominence after the KPB in parallel with several well-studied animal clades including Placentalia and Neoaves. Furthermore, multiple WGD events are hypothesized to have occurred early in legume evolution. Using a recently inferred phylogenomic framework, we investigate the placement of WGDs during early legume evolution using gene tree reconciliation methods, gene count data and phylogenetic supernetwork reconstruction. Using 20 fossil calibrations we estimate a revised timeline of legume evolution based on 36 nuclear genes selected as informative and evolving in an approximately clock-like fashion. To establish the timing of WGDs we also date duplication nodes in gene trees. Results suggest either a pan-legume WGD event on the stem lineage of the family, or an allopolyploid event involving (some of) the earliest lineages within the crown group, with additional nested WGDs subtending subfamilies Papilionoideae and Detarioideae. Gene tree reconciliation methods that do not account for allopolyploidy may be misleading in inferring an earlier WGD event at the time of divergence of the two parental lineages of the polyploid, suggesting that the allopolyploid scenario is more likely. We show that the crown age of the legumes dates to the Maastrichtian or early Paleocene and that, apart from the Detarioideae WGD, paleopolyploidy occurred close to the KPB. We conclude that the early evolution of the legumes followed a complex history, in which multiple auto- and/or allopolyploidy events coincided with rapid diversification and in association with the mass extinction event at the KPB, ultimately underpinning the evolutionary success of the Leguminosae in the Cenozoic.

中文翻译：

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豆科植物的起源是一个复杂的古多倍体系统发育缠结，与白垩纪-古近纪 (K-Pg) 大灭绝事件密切相关

白垩纪-古近纪 (K-Pg) 边界 (KPB) 大灭绝对植物多样性进化的影响仍然知之甚少，尽管 KPB 植物谱系的进化更替是理解新生代生物群的核心。KPB 周围全基因组重复 (WGD) 事件的明显浓度可能在植物谱系的存活和随后的多样化中发挥了作用。为了获得对新生代生物多样性起源的新见解，我们研究了全球多样化豆科植物（豆科或豆科）的起源和早期进化。豆科植物在许多植被类型中在生态上（共同）占主导地位，化石记录表明，它们在 KPB 之后与几个经过充分研究的动物进化枝（包括胎盘类和 Neoaves）同时上升到如此突出的地位。此外，假设在豆科植物进化的早期发生了多个 WGD 事件。使用最近推断的系统发育框架，我们使用基因树协调方法、基因计数数据和系统发育超网络重建研究了早期豆科植物进化过程中 WGD 的位置。使用 20 个化石校准，我们根据 36 个被选为提供信息并以近似时钟的方式进化的核基因来估计豆科植物进化的修订时间表。为了确定 WGD 的时间，我们还在基因树中确定了重复节点的日期。结果表明，该科的茎谱系发生了泛豆科植物 WGD 事件，或者涉及冠群中（一些）最早谱系的异源多倍体事件，以及额外的嵌套 WGD 对着蝶形科和蝶形科的亚科。