The lycophyte genus Selaginella alone constitutes the family Selaginellaceae, the largest of the lycophyte families. The genus is estimated to contain 700-800 species distributed on all continents except Antarctica, with highest species diversity in tropical and subtropical regions. The monophyly of Selaginella in this broad sense has rarely been doubted, whereas its intrageneric classification has been notoriously contentious. Previous molecular studies were based on very sparse sampling of Selaginella (up to 62 species) and often used DNA sequence data from one genome. In the present study, DNA sequences of one plastid (rbcL) and one nuclear (ITS) locus from 394 accessions representing approximately 200 species of Selaginella worldwide were used to infer a phylogeny using maximum likelihood, Bayesian inference and maximum parsimony methods. The study identifies strongly supported major clades and well resolves relationships among them. Major results include: (i) six deep-level clades are discovered representing the deep splits of Selaginella; and (ii) 20 major clades representing 20 major evolutionary lineages are identified, which differ from one another in molecular, macro-morphological, ecological and spore features, and/or geographical distribution.

Polyploidy is widely considered as a major process in the evolution of plants but the accumulation of polyploid species diversity is still controversial. Some recent studies proposed increased extinction risk in neopolyploids compared with their diploid ancestors. The high proportion of polyploid ferns is expected to be formed mainly by neopolyploids, whereas paleopolyploid species are predicted to be clustered in clades founded by whole genome duplications. Here, we test this prediction by exploring the evolution of polyploidy in the derived fern family Aspleniaceae. The family has a global distribution and shows the highest frequency of polyploid taxa among all ferns. To test the hypothesis, we obtained a comprehensive phylogeny using chloroplast DNA sequences of 883 specimens representing 292 species. All published chromosome counts were mapped onto this phylogenetic framework in order to explore the evolution of polyploids. We recovered evidence for several whole genome duplications in the history of Aspleniaceae. Phylogenetic relationships of polyploids exceeding the tetraploid level suggest that tetraploid Asplenium species may have replaced their diploid ancestors as the main evolutionary players in some clades of this family.

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The infrageneric relationships and taxonomy of the largest fern genus, Asplenium (Aspleniaceae), have remained poorly understood. Previous studies have focused mainly on specific species complexes involving a few or dozens of species only, or have achieved a large taxon sampling but only one plastid marker was used. In the present study, DNA sequences from six plastid markers (atpB, rbcL, rps4, rps4-trnS, trnL and trnL-F) of 1030 accessions (616 of them newly sequenced here) representing c. 420 species of Asplenium (60% of estimated species diversity), 16 species of Hymenasplenium, three Diplaziopsidaceae, and four Rhachidosoraceae were used to produce the largest genus-level phylogeny yet for ferns. Our major results include: (i) Asplenium as broadly circumscribed is monophyletic based on our inclusion of representatives of 32 of 38 named segregate genera; (ii) 11 major clades in Asplenium are identified, and their relationships are mostly well-resolved and strongly supported; (iii) numerous species, unsampled in previous studies, suggest new relationships and numerous cryptic species and species complexes in Asplenium; and (iv) the accrued molecular evidence provides an essential foundation for further investigations of complex patterns of geographical diversification, speciation and reticulate evolution in this family.

Grammitidoideae are the largest subfamily in Polypodiaceae and contain about 911 species. Progress has been made in understanding the overall phylogeny and generic boundaries in the light of recent molecular works. However, the majority of species, especially Asian species, and some critical type species of genera remain unsampled. In this study, a dataset of six plastid markers of 1003 (112 new) accessions representing ca. 412 species of Grammitidoideae including the type species of Ctenopterella, Grammitis, Moranopteris, Radiogrammitis, and Themelium, was assembled to infer a phylogeny. Our major results include: (1) the type species of Grammitis is successfully sequenced using a next‐generation sequencing technique and is resolved in Grammitis s.str. as expected; (2) Ctenopterella is found to be polyphyletic and a new clade consisting of C. khaoluangensis is resolved as sister to Tomophyllum; (3) the type species of Ctenopterella is resolved in a clade sister to the C. lasiostipes clade; (4) Oreogrammitis is found to be polyphyletic and three clades outside of the core Oreogrammitis are identified containing O. subevenosa and allies, O. orientalis, and O. beddomeana (+ O. cf. beddomeana); (5) Prosaptia is found to be paraphyletic with P. nutans being sister to a clade containing the rest of Prosaptia and Archigrammitis; (6) the intergeneric and major relationships within the Asia‐Pacific clade are well resolved and strongly supported except for a few branches; (7) extensive cryptic speciation is detected in the Asia‐Pacific clade; and (8) based on the polyphyly of Ctenopterella we describe three new genera, Boonkerdia, Oxygrammitis, and Rouhania, for species formerly in Ctenopterella; because the type species of Grammitis belongs to Grammitis s.str., we describe five new genera, Aenigmatogrammitis, Grammitastrum (stat. nov.), Howeogrammitis, Nanogrammitis, and Thalassogrammitis for species formerly in Grammitis s.l. A key to the 35 Old‐World genera is given, a taxonomic treatment is presented, and the morphology of all new genera is shown with either a color plate and/or a line drawing.

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