State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; China National Botanical Garden, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; China National Botanical Garden, Beijing 100093, China.
Mol Phylogenet Evol. 2023 Sep;186:107870. doi: 10.1016/j.ympev.2023.107870. Epub 2023 Jul 3.
The deciduous broad-leaved forests (DBLFs) cover large temperate and subtropical high-altitude regions in the Northern Hemisphere. They are home to rich biodiversity, especially to numerous endemic and relict species. However, we know little about how this vegetation in the Northern Hemisphere has developed through time. Here, we used Actaea (Ranunculaceae), an herbaceous genus almost exclusively growing in the understory of the Northern Hemisphere DBLFs, to shed light on the historical assembly of this biome in the Northern Hemisphere. We present a complete species-level phylogenetic analysis of Actaea based on five plastid and nuclear loci. Using the phylogenetic framework, we estimated divergence times, ancestral ranges, and diversification rates. Phylogenetic analyses strongly support Actaea as monophyletic. Sections Podocarpae and Oligocarpae compose a clade, sister to all other Actaea. The sister relationship between sections Chloranthae and Souliea is strongly supported. Section Dichanthera is not monophyletic unless section Cimicifuga is included. Actaea originated in East Asia, likely the Qinghai-Tibet Plateau, in the late Paleocene (c. 57 Ma), and subsequently dispersed into North America in the middle Eocene (c. 43 Ma) via the Thulean bridge. Actaea reached Europe twice, Japan twice, and Taiwan once, and all these five colonization events occurred in the late Miocene-early Pliocene, a period when sea level dropped. Actaea began to diversify at c. 43 Ma. The section-level diversification took place at c. 27-37 Ma and the species-level diversification experienced accelerations twice, which occurred at c. 15 Ma and c. 5 Ma, respectively. Our findings suggest that the Northern Hemisphere DBLFs might have risen in the middle Eocene and further diversified in the late Eocene-Oligocene, middle Miocene and early Pliocene, in association with climatic deterioration during these four periods.
落叶阔叶林（DBLFs）覆盖了北半球中高海拔的大片温带和亚热带地区。它们是丰富生物多样性的家园，尤其是许多特有和遗留物种。然而，我们对北半球这种植被是如何随着时间的推移而发展的知之甚少。在这里，我们使用毛茛科（Ranunculaceae）草本属Actaea，它几乎完全生长在北半球落叶阔叶林的林下，以揭示北半球这种生物群落的历史组合。我们基于五个质体和核基因座，提供了 Actaea 的完整种系发生分析。使用系统发育框架，我们估计了分歧时间、祖先范围和多样化率。系统发育分析强烈支持 Actaea 是单系的。Podocarpae 和 Oligocarpae 两个组构成一个分支，与所有其他 Actaea 分支互为姐妹群。Chloranthae 和 Souliea 两个组之间的姐妹关系得到了强烈支持。除非包括 Cimicifuga 组，否则 Dichanthera 组不是单系的。Actaea 起源于东亚，可能是青藏高原，在古近纪晚期（约 57 Ma），随后通过 Thulean 桥在中始新世（约 43 Ma）扩散到北美洲。Actaea 两次到达欧洲，两次到达日本，一次到达台湾，所有这五次殖民事件都发生在中新世-上新世早期，当时海平面下降。Actaea 大约在 43 Ma 开始多样化。组水平的多样化发生在大约 27-37 Ma，物种水平的多样化经历了两次加速，分别发生在大约 15 Ma 和 5 Ma。我们的研究结果表明，北半球的 DBLFs 可能在中始新世兴起，并在随后的渐新世-始新世晚期、中新世中期和上新世早期进一步多样化，与这四个时期的气候恶化有关。
