Phylogenetic Diversity and Evolutionary Relationships of Ferns

Ferns represent a globally distributed lineage of monilophytes encompassing roughly 12 000 species, second only to flowering plants in vascular plant diversity. Their evolutionary history stretches back more than 360 million years, with fossil and molecular data together illuminating deep splits among horsetails, ophioglossoid ferns, marattioid ferns and leptosporangiate clades. Modern phylogenetic frameworks integrate plastid, nuclear and genomic structural markers to resolve a robust backbone phylogeny in which Equisetales (horsetails) emerge as sister to all other ferns, Dennstaedtiaceae as sister to eupolypods and further subdivisions among major families. This tree of life underpins studies of morphological innovation—such as the origin of sporangial annuli and novel leaf forms—and reveals repeated convergences in life-history traits. Fern diversification has been driven by a dynamic interplay of origination and extinction, with environmental shifts governing palaeo-extinction pulses and episodic radiations tied to ecological opportunity. From canopy specialists recruiting ant bodyguards via independently evolved nectaries to ground-layer pioneers facilitating soil stabilisation after disturbance, ferns exhibit both competitive and facilitative strategies that have shaped terrestrial ecosystems from the Cretaceous to the present. Ongoing integration of high-throughput sequencing, fossil calibration and automated phylogenomic pipelines is expanding taxon sampling, refining divergence-time estimates and revealing cryptic diversity, with broad implications for conservation, ecosystem restoration and understanding plant resilience in a changing climate.

Research from Nature Portfolio

Recent studies have uncovered a remarkable case of convergent evolution in which ant-guarding nectaries originated independently in ferns and flowering plants during the Cretaceous. Ferns appear to have evolved sugary secretions that recruit ant bodyguards only after a prolonged lag, diversifying nectary-bearing lineages in the Cenozoic as they colonised forest canopies and co-opted pre-existing ant–angiosperm associations for defence. Complementing this, a combined analysis of fossil occurrences and a large molecular phylogeny has shown that fern diversity dynamics are governed by fundamentally distinct processes: origination rates respond opportunistically to available ecospace, whereas extinction rates track external environmental drivers such as climate fluctuations and geological upheaval. These findings highlight extinction as the prime force shaping long-term fern diversity and underscore the value of integrating neontological and palaeontological data.

Phylogenetic Diversity and Evolutionary Relationships of Ferns publication trend

The graph below shows the total number of articles in phylogenetic diversity and evolutionary relationships of ferns across all publications each year (not limited to Nature Index journals).

Technical terms

Phylogenetic diversity: A measure of the total evolutionary history represented among a set of taxa, typically quantified by the sum of branch lengths in a phylogenetic tree.

Backbone phylogeny: The principal framework of evolutionary relationships among major clades within a larger taxonomic group.

Sporangium (plural sporangia): A specialised structure in ferns that produces and releases spores for reproduction.

Origination rate: The frequency at which new species arise within a lineage over time.

Extinction rate: The frequency at which species within a lineage become extinct over time.

Plastome: The complete genome of a plastid, most often referring to the chloroplast genome used in plant phylogenetics.

References

1. Convergent evolution of fern nectaries facilitated independent recruitment of ant-bodyguards from flowering plants. Nature Communications (2024).
2. Ferns as facilitators of community recovery following biotic upheaval. BioScience (2024).
3. Large-scale phylogenomic analysis resolves a backbone phylogeny in ferns. GigaScience (2017).
4. Environmentally driven extinction and opportunistic origination explain fern diversification patterns. Scientific Reports (2017).
5. Complete plastid genomes from Ophioglossum californicum, Psilotum nudum, and Equisetum hyemale reveal an ancestral land plant genome structure and resolve the position of Equisetales among monilophytes. BMC Ecology and Evolution (2013).
6. An open and continuously updated fern tree of life. Frontiers in Plant Science (2022).