Phylogeny and divergence of Chinese Angiopteridaceae based on chloroplast DNA sequence data (rbcL and trnL-F)

Abstract

Marattioid ferns are an ancient lineage of primitive vascular plants that first appeared in the middle Carboniferous. Extant members are almost exclusively restricted to tropical regions, and the species-rich family Angiopteridaceae are limited in their distribution to the eastern hemisphere; relationships within the group are currently vague. Here the phylogenetic relationship between Angiopteris Hoffm. and Archangiopteris Christ et Gies. was evaluated based on the sequence analysis of chloroplast rbcL gene and trnL-F intergenic spacer with MEGA2 and MrBayes v3.0b4. On the basis of the phylogenetic pattern and fossil record, we further estimated the divergence time for the two genera. The phylogenetic trees revealed that all species of Angiopteris and Archangiopteris in this study formed a monophyletic group with strong statistical support, but the relationship between the two genera remained unresolved based on individual sequence analysis. On the other hand, the sequence analyses of combined data set revealed that Archangiopteris species diverged first, indicating that Archangiopteris may not be a direct derivative as traditionally assumed. The clade of Angiopteris and Archangiopteris appears to have diversified in the late Oligocene (≈26 Ma) based on the molecular estimate. Thus, the evolutionary history of extant Angiopteris and Archangiopteris has been characterized by ancient origin and recent diversification, and these groups are not relic and endangered lineages as traditionally considered.