TITLE:
Dating Suborder Polypodiineae (Eupolypods I) with Its Oldest Fossil
AUTHORS:
Chunxiang Li, Junye Ma
KEYWORDS:
Eupolypods, Polypodiineae, Dryopteridaceae Fossils, Bayesian Tip-Dating
JOURNAL NAME:
Open Journal of Geology,
Vol.14 No.10,
October
30,
2024
ABSTRACT: Inferring divergence times between lineages is crucial for understanding biological evolutionary processes. The extraordinary species diversity of Eupolypods within the fern lineage has been interpreted as an ecological opportunistic response to the emergence of more complex, angiosperm-dominated ecosystems. This co-adaptation between Eupolypods and angiosperms has prompted ongoing investigations into the phylogenetic and diversification timelines of Eupolypods. In this study, we incorporate newly discovered fossils of Dryopteridaceae, including two species from both the stem and crown groups, to reanalyze the phylogenetic and diversification times of Eupolypods using total-evidence dating (TED or tip-dating) methods. Our analyses confirm that Eupolypods first diversified during the Jurassic and suggest that both subclades, Polypodiineae and Aspleniineae, underwent their earliest diversification during this period, challenging recent claims that Polypodiineae diversified no earlier than the Cretaceous. These results support a “long fuse” model, indicating that the initial emergence of Polypodiales preceded their diversification and extensive fossil record. Furthermore, our findings clarify the systematic position of Hypodematiaceae, indicating that it, along with Didymochlaenaceae, represents the basal lineages of Polypodiineae. This study highlights the critical role of fossil abundance and taxonomic composition in molecular dating analyses.