"非洲起源"支持的泛热带鹿角蕨属（水龙骨科）的质体系统发育基因组学和生物地理学分析。
'Out of Africa' origin of the pantropical staghorn fern genus Platycerium (Polypodiaceae) supported by plastid phylogenomics and biogeographical analysis.
机构信息
College of Horticulture and Landscape Architecture, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China.
Guangxi Nanning Roy Garden Co., Ltd, Nanning 530227, China.
出版信息
Ann Bot. 2024 May 10;133(5-6):697-710. doi: 10.1093/aob/mcae003.
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, 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 a focus on Platycerium species, and further conducted molecular dating and biogeographical analyses of the genus.
KEY RESULTS
The present analyses yielded a robustly supported phylogenetic hypothesis of Platycerium. Molecular dating results showed that Platycerium split from its sister genus Hovenkampia ~35.2 million years ago (Ma) near the Eocene-Oligocene boundary and began to diverge ~26.3 Ma during the late Oligocene, while multiple speciation events within Platycerium occurred during the middle to late Miocene. Biogeographical analysis suggested that Platycerium originated in tropical Africa and then dispersed eastward to southeast Asia-Australasia and westward to neotropical areas.
CONCLUSIONS
Our analyses using a plastid phylogenomic approach improved our understanding of the species-level relationships within Platycerium. The global climate changes of both the Late Oligocene Warming and the cooling following the mid-Miocene Climate Optimum may have promoted the speciation of Platycerium, and transoceanic long-distance dispersal is the most plausible explanation for the pantropical distribution of the genus today. Our study investigating the biogeographical history of Platycerium provides a case study not only for the formation of the pantropical intercontinental disjunction of this fern genus but also the 'out of Africa' origin of plant lineages.
背景与目的
鹿角蕨属（Platycerium）是最常被栽培的观赏蕨类之一，其物种广泛分布于热带地区，形成洲际间断分布。然而，该属种间关系尚未得到很好的解决，其时空进化历史也需要进一步探索。
方法
本研究对所有 18 种鹿角蕨的质体基因组进行了新的测序。利用质体基因组数据，重建了水龙骨科成员的系统发育关系，重点关注鹿角蕨属物种，并进一步进行了该属的分子定年和生物地理学分析。
主要结果
本研究分析得到了一个强有力的鹿角蕨属系统发育假说。分子定年结果表明，鹿角蕨与其姐妹属霍文坎普蕨（Hovenkampia）在始新世-渐新世之交（约 3520 万年前）分化，在渐新世晚期（约 2630 万年前）开始分化，而鹿角蕨属内的多次物种形成事件发生在中新世中期至晚期。生物地理学分析表明，鹿角蕨起源于热带非洲，然后向东扩散到东南亚-澳大拉西亚，向西扩散到新热带地区。
结论
本研究利用质体基因组学方法分析了鹿角蕨属内的种间关系，加深了我们对该属的认识。晚渐新世变暖事件和中中新世气候最优期之后的冷却事件等全球气候变化可能促进了鹿角蕨的物种形成，而跨洋长距离扩散是该属现今广泛分布于热带地区的最合理解释。本研究对鹿角蕨生物地理学历史的研究不仅为该蕨类属种的泛热带洲际间断分布提供了案例，也为植物谱系的“非洲起源”提供了案例。
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