School of Ecology and Environmental Science, Yunnan University, Kunming 650504, Yunnan, China.
Gardening and Horticulture Center, Xishuangbanna Tropic Botanical Garden, Chinese Academy of Sciences, Mengla 666303, Yunnan, China.
Mol Phylogenet Evol. 2024 Dec;201:108213. doi: 10.1016/j.ympev.2024.108213. Epub 2024 Oct 10.
Platycerium is a genus of pantropical epiphytic ferns consisting of ca. 18 species and are highly sought after by horticultural enthusiasts. Although the monophyly of this genus has been well supported in previous molecular studies, as an intercontinentally disjunct genus, the origin and distribution pattern of Platycerium were elusive and controversial. This is mainly due to limited taxon sampling, a plastid representing only a single coalescent history, the lack of fossil evidence, and so on. Here, by utilizing genome-skimming sequencing, transcriptome sequencing, and flow cytometry, we integrated chloroplast genomes, data of single-copy nuclear genes, ploidy levels, morphology, and geographic distribution to understand the species phylogeny and the evolutionary and biogeographic history of Platycerium. Our major results include: (1) based on both plastid and nuclear datasets, Platycerium is consistently resolved into three fully supported clades: the Afro-American (AA) clade, the Javan-Australian (JA) clade, and the Malayan-Asian (MA) clade. The AA clade and MA clade are further divided into three and two subclades, respectively; (2) a large amount of gene tree conflict, as well as cytonuclear discordance, was found and can be explained by hybridization and incomplete lineage sorting, and most of the hybridization hypotheses represented ancient hybridization events; (3) through molecular dating, the crown age of Platycerium is determined to be at approximately 32.79 Ma based on the plastid dataset or 29.08 Ma based on the nuclear dataset in the Middle Oligocene; (4) ancestral area reconstruction analysis from different datasets showed that Platycerium most likely originated from Indochina; (5) current distribution patterns are resultant from long-distance dispersals, ancient orogeny, and an ancient climate event; and (6) species diversification was driven by polyploidization, dispersal, and hybridization. This study presented here will help understand the evolution of tropical plant flora and provide a reference for the cultivation and breeding of staghorn ferns.
鹿角蕨属是一个泛热带附生蕨类植物属，包含约 18 个物种，深受园艺爱好者的追捧。尽管该属的单系性在先前的分子研究中得到了很好的支持，但作为一个洲际间断分布的属，鹿角蕨属的起源和分布模式仍然难以捉摸，存在争议。这主要是由于有限的分类群采样、代表单一融合历史的质体、缺乏化石证据等原因。在这里，我们通过利用基因组扫描测序、转录组测序和流式细胞术，整合质体基因组、单拷贝核基因数据、倍性水平、形态和地理分布，来了解鹿角蕨属的物种系统发育以及该属的进化和生物地理历史。我们的主要结果包括：（1）基于质体和核数据集，鹿角蕨属始终被分为三个完全支持的分支：非洲-美洲（AA）分支、爪哇-澳大利亚（JA）分支和马来-亚洲（MA）分支。AA 分支和 MA 分支分别进一步分为三个和两个亚分支；（2）发现了大量的基因树冲突以及核质不和谐，这可以用杂交和不完全谱系分选来解释，并且大多数杂交假说代表了古老的杂交事件；（3）通过分子定年，基于质体数据集，鹿角蕨属的冠层年龄确定为约 32.79 Ma，或基于核数据集在中始新世的 29.08 Ma；（4）来自不同数据集的祖先区重建分析表明，鹿角蕨属最有可能起源于印度支那；（5）当前的分布格局是由长距离扩散、古老造山运动和古老气候事件造成的；（6）物种多样化是由多倍化、扩散和杂交驱动的。本研究有助于了解热带植物区系的进化，并为鹿角蕨的栽培和繁殖提供参考。
