Abstract
Phymatopteris Pic. Serm., a derived polypodiaceous fern, is one of the many fern genera that still suffer from nomenclatural confusion. Its generic circumscription and phylogenetic relationships with other selligueoid ferns have been controversial, and its geographic origin, whether in the Himalayan region of continental Asia or in Malay Archipelago, is still unknown. A phylogeny of all selligueoid ferns based on 4 cpDNA (rbcL, trnL-F, rps4 and rps4-trnS) regions indicates that Phymatopteris is not monophyletic. Phymatopteris species are distributed in 5 well-supported clades that can be distinguished with frond-shape and frond-margin characters. All early-divergent species are from the Malaysian Archipelago, while the remaining species are all from the Himalayan region and form a recently diverged group that is largely unresolved, most likely having resulted from an explosive radiation. Divergence-time estimation suggests that the first diversification of selligueoid ferns occurred at ca. 27 Ma in the Malaysian Archipelago, followed by migration into the Himalayan region around 20 Ma. The radiation of the Himalayan species occurred mostly within the last 20 million years, within the period of recent major uplifts of the Qinghai-Tibetan Plateau (between the early Miocene and the Pleistocene) and late-Cenozoic global cooling. Our evidence leads us to propose that the Malaysian Archipelago is the ancestral area for Phymatopteris.
Highlights
Phymatopteris was established by Pichi Sermolli in 1973 to replace Phymatopsis J
maximum parsimony (MP), maximum likelihood (ML) and Bayesian inference (BI) analyses of the 4 combined sequences resulted in nearly identical topologies, most differences were in statistical support values
Because the resultant topologies for relationships of the selligueoid ferns from each of the datasets were not in conflict with one another, the phylogenetic relationships presented here are based on analyses of the combined data set
Summary
Phymatopteris was established by Pichi Sermolli in 1973 to replace Phymatopsis J. Shao et al [9,10,11,12] accepted Ching’s [6] Phymatopteris as a natural group and examined spore ornamentations, characters of scales, leaf epidermises, and leaf appendages, with the goal of identifying morphological characters for a revised classification Their results suggested that the characteristics of the leaves, scales, and spores cannot serve as a criterion of distinguishing the series and subseries in Phymatopteris. Ching [20] regarded Phymatopteris species to have their origin in the Himalayan region of continental Asia; he saw the Malay and Polynesian species in this alliance as being the result of later migration and speciation events This idea, accepted by most Chinese fern researchers, is in opposition to the recent finding that the Malay Archipelago is the putative ancestral area for selligueoid ferns [19] including Phymatopteris, which is included in Selliguea in their circumscription
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