Background and Aims The staghorn fern genus Platycerium is one of the most commonly grown ornamental ferns, and it evolved to occupy a typical pantropical intercontinental disjunction. However, the species-level relationships in the genus have not been well-resolved, and the spatiotemporal evolutionary history of the genus also needs to be explored. Methods Plastomes of all the 18 Platycerium species were newly sequenced. Using plastome data, we reconstructed the phylogenetic relationships among Polypodiaceae members with the focus on Platycerium species, and further conducted molecular dating and biogeographic analyses of the genus. Key Results The present analyses yielded a robustly supported phylogenetic hypothesis of Platycerium. Molecular dating result showed that Platycerium split from its sister genus Hovenkampia at ~35.2 million years ago (Ma) near the Eocene-Oligocene boundary and began to diverge at ~26.3 Ma during the late Oligocene, while multiple speciation events within Platycerium occurred during the middle to late Miocene. Biogeographic analysis suggested that Platycerium originated in tropical Africa and then dispersed eastward to southeast Asia-Australasia and westward to neotropical area. Conclusions Our analyses using plastid phylogenomic approach improved understanding the species-level relationships within Platycerium. The global climate changes of both the Late-Oligocene Warming (LOW) and the cooling following the mid-Miocene Climate Optimum (MMCO) may have promoted the speciation of Platycerium, and the transoceanic long-distance dispersal (LLD) is the most plausible explanation for the genus attained its pantropical distribution. Our study to investigate the biogeographic history of Platycerium provides a case study not only for the formation of the pantropical intercontinental disjunction of fern genus but also the ‘out of Africa’ origin of plant lineages.

中文翻译：

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质体系统发育学和生物地理学分析支持泛热带鹿角蕨属 Platycerium（水龙骨科）的“非洲”起源

背景和目的鹿角蕨属Platycerium是最常见的观赏蕨类植物之一，它进化到占据了典型的泛热带洲际分界处。然而，属内的种级关系尚未得到很好的解决，属的时空进化史也有待探索。方法对所有18个Platycerium物种的质体进行新测序。利用质体组数据，我们以扁藻属物种为重点，重建了水龙骨科成员之间的系统发育关系，并进一步对该属进行了分子测年和生物地理学分析。主要结果 目前的分析得出了一个强有力的支持 Platycerium 的系统发育假说。分子测年结果显示，Platycerium于约3520万年前（Ma）在始新世-渐新世边界附近从其姐妹属Hovenkampia分裂，并在渐新世晚期约26.3 Ma开始分歧，而Platycerium内部发生了多个物种形成事件在中期到中新世晚期。生物地理学分析表明，Platycerium起源于热带非洲，然后向东传播到东南亚-澳大利亚，向西传播到新热带地区。结论我们使用质体系统发育学方法进行的分析提高了对 Platycerium 内物种水平关系的理解。渐新世晚期变暖（LOW）和中中新世气候最适期（MMCO）之后的降温的全球气候变化可能促进了Platycerium的物种形成，而跨洋长距离扩散（LLD）是最合理的解释因为该属已达到泛热带分布。我们对 Platycerium 生物地理学历史的研究不仅为蕨类植物属泛热带洲际分离的形成提供了案例研究，而且还为植物谱系的“非洲之外”起源提供了案例研究。