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Premise: Approximately 14% of all fern species have physiologically active chlorophyllous spores that are much more short-lived than the more common and dormant achlorophyllous spores. Most chlorophyllous-spored species (70%) are epiphytes and account for almost 37% of all epiphytic ferns. Chlorophyllous-spored ferns are also overrepresented among fern species in habitats with waterlogged soils, of which nearly 60% have chlorophyllous spores. Ferns in these disparate habitat types also have a low incidence of mycorrhizal associations. We therefore hypothesized that autotrophic chlorophyllous spores represent an adaptation of ferns to habitats with scarce mycorrhizal associations., Methods: We evaluated the coevolution of chlorophyllous spores and mycorrhizal associations in ferns and their relation to habitat type using phylogenetic comparative methods., Results: Although we did not find support for the coevolution of spore type and mycorrhizal associations, we did find that chlorophyllous spores and the absence of mycorrhizal associations have coevolved with epiphytic and waterlogged habitats. Transition rates to epiphytic and waterlogged habitats were significantly higher in species with chlorophyllous spores compared to achlorophyllous lineages., Conclusions: Spore type and mycorrhizal associations appear to play important roles in the radiation of ferns into different habitat types. Future work should focus on clarifying the functional significance of these associations., (© 2022 The Authors. American Journal of Botany published by Wiley Periodicals LLC on behalf of Botanical Society of America.)

Phylogenetic divergence-time estimation has been revolutionized by two recent developments: 1) total-evidence dating (or "tip-dating") approaches that allow for the incorporation of fossils as tips in the analysis, with their phylogenetic and temporal relationships to the extant taxa inferred from the data and 2) the fossilized birth-death (FBD) class of tree models that capture the processes that produce the tree (speciation, extinction, and fossilization) and thus provide a coherent and biologically interpretable tree prior. To explore the behavior of these methods, we apply them to marattialean ferns, a group that was dominant in Carboniferous landscapes prior to declining to its modest extant diversity of slightly over 100 species. We show that tree models have a dramatic influence on estimates of both divergence times and topological relationships. This influence is driven by the strong, counter-intuitive informativeness of the uniform tree prior, and the inherent nonidentifiability of divergence-time models. In contrast to the strong influence of the tree models, we find minor effects of differing the morphological transition model or the morphological clock model. We compare the performance of a large pool of candidate models using a combination of posterior-predictive simulation and Bayes factors. Notably, an FBD model with epoch-specific speciation and extinction rates was strongly favored by Bayes factors. Our best-fitting model infers stem and crown divergences for the Marattiales in the mid-Devonian and Late Cretaceous, respectively, with elevated speciation rates in the Mississippian and elevated extinction rates in the Cisuralian leading to a peak diversity of ${\sim}$2800 species at the end of the Carboniferous, representing the heyday of the Psaroniaceae. This peak is followed by the rapid decline and ultimate extinction of the Psaroniaceae, with their descendants, the Marattiaceae, persisting at approximately stable levels of diversity until the present. This general diversification pattern appears to be insensitive to potential biases in the fossil record; despite the preponderance of available fossils being from Pennsylvanian coal balls, incorporating fossilization-rate variation does not improve model fit. In addition, by incorporating temporal data directly within the model and allowing for the inference of the phylogenetic position of the fossils, our study makes the surprising inference that the clade of extant Marattiales is relatively young, younger than any of the fossils historically thought to be congeneric with extant species. This result is a dramatic demonstration of the dangers of node-based approaches to divergence-time estimation, where the assignment of fossils to particular clades is made a priori (earlier node-based studies that constrained the minimum ages of extant genera based on these fossils resulted in much older age estimates than in our study) and of the utility of explicit models of morphological evolution and lineage diversification. [Bayesian model comparison; Carboniferous; divergence-time estimation; fossil record; fossilized birth-death; lineage diversification; Marattiales; models of morphological evolution; Psaronius; RevBayes.]., (© The Author(s) 2021. Published by Oxford University Press, on behalf of the Society of Systematic Biologists.)

Acrospermum is a poorly known genus of epibiotic and saprophytic species with a subcosmopolitan distribution. Here, we investigate the intriguing relationship between Acrospermum and its host plants in the fern family Polypodiaceae, where it occurs upon approximately 45 neotropical species. We conducted phylogenetic analyses using an eight-marker comprehensive ascomycete data set comprising 719 species representing all major lineages along with 23 new Acrospermum specimens sampled from ferns. We ask whether fern-dwelling Acrospermum are monophyletic, whether epibiotic Acrospermum have evolved independently from saprophytic ancestors, and identify anamorphic phases by incorporating sequences for all suspected taxa. Our results corroborate the placement of Acrospermales within the Dothideomycetes with strong support. However, the order remains incertae sedis due to weak support along the branches subtending the clade that includes the Acrospermales plus Dyfrolomycetales. Our results show a strong phylogenetic pattern in lifestyles but do not clearly identify an ancestral life history state. The first divergence in Acrospermaceae splits fungicolous taxa from taxa that inhabit plants; saprophytes and anamorphic phases found on angiosperms occur in both clades. Fungicolous species are monophyletic, whereas species with an epibiotic or necrotic life history upon plants are nonmonophyletic due to the position of the saprophyte A. longisporium . Previously, all Acrospermum collected from ferns were identified as A. maxonii . Our results indicate that this is not monophyletic due to the inclusion of Gonatophragmium triuniae . Two species are described herein as A. gorditum , sp. nov., and A. leucocephalum , sp. nov. We find no instances of co-cladogenesis; however, our ability to detect this is limited by the lack of resolution in the A. maxonii clade. Rather, we see that that the distribution of epibiotic Acrospermum is explained by the overlap between the ecological niche of the Acrospermum species and its host.

Premise of the Study: Understanding the relationship between phenotypic evolution and lineage diversification is a central goal of evolutionary biology. To extend our understanding of the role morphological evolution plays in the diversification of plants, we examined the relationship between leaf size evolution and lineage diversification across ferns., Methods: We tested for an association between body size evolution and lineage diversification using a comparative phylogenetic approach that combined a time-calibrated phylogeny and leaf size data set for 2654 fern species. Rates of leaf size change and lineage diversification were estimated using BAMM, and rate correlations were performed for rates obtained for all families and individual species. Rates and patterns of rate-rate correlation were also analyzed separately for terrestrial and epiphytic taxa., Key Results: We find no significant correlation between rates of leaf area change and lineage diversification, nor was there a difference in this pattern when growth habit is considered. Our results are consistent with the findings of an earlier study that reported decoupled rates of body size evolution and diversification in the Polypodiaceae, but conflict with a recent study that reported a positive correlation between body size evolution and lineage diversification rates in the tree fern family Cyatheaceae., Conclusions: Our findings indicate that lineage diversification in ferns is largely decoupled from shifts in body size, in contrast to several other groups of organisms. Speciation in ferns appears to be primarily driven by hybridization and isolation along elevational gradients, rather than adaptive radiations featuring prominent morphological restructuring. The exceptional diversity of leaf morphologies in ferns appears to reflect a combination of ecophysiological constraints and adaptations that are not key innovations., (© 2018 Botanical Society of America.)

Based on a worldwide phylogenetic framework filling the taxonomic gap of Madagascar and surrounding islands of the Western Indian Ocean (WIO), we revisited the systematics of grammitid fern species (Polypodiaceae). We also investigated the biogeographic origin of the extant diversity in Madagascar and estimated the relative influence of vicariance, long-distance dispersals (LDD) and in situ diversification. Phylogenetic inferences were based on five plastid DNA regions (atpB, rbcL, rps4-trnS, trnG-trnR, trnL-trnF) and the most comprehensive taxonomic sampling ever assembled (224 species belonging to 31 out of 33 recognized grammitids genera). 31 species from Madagascar were included representing 87% of the described diversity and 77% of the endemics. Our results confirmed a Paleotropical clade nested within an amphi-Atlantic grade. In addition, we identified three new major clades involving species currently belonging to Grammitis s.l., Ctenopterella and Enterosora. We resolved for the first time Grammitis s.s. as monophyletic, and Ctenopterella (newly tested here) and Enterosora as polyphyletic. The Neotropical genus Moranopteris was shown to also occur in Madagascar through a newly discovered species. Most importantly, we suggest a >30% inflation of the species number in the WIO due to the hidden diversity in >10 cryptic lineages, best explained by high morphological homoplasy. Molecular dating and ancestral areas reconstruction allowed identifying the Neotropics as the predominant source of LDD to the African-WIO region, with at least 12 colonization events within the last 20Ma. Repeated eastward migrations may be explained by transoceanic westerly winds transporting the dust-like spores. Tropical Asia s.l. would also have played a (minor) role through one dispersal event to Madagascar at the end of the Oligocene. Last, within the complex Malagasy region made of a mosaic of continental and oceanic islands located close to the African continent, we showed that contrary to theoretical expectations and empirical evidence in angiosperms, Africa does not act as a dispersal source and Madagascar seems to have a more important influence on the regional dynamics: we observed both in situ species diversification and dispersal out of Madagascar. This influence also extends beyond the region, since one dispersal event probably originated from Madagascar and reached the Subantarctic island of Amsterdam., (Copyright © 2017 Elsevier Inc. All rights reserved.)

A recent study has documented a natural hybridization event between two fern lineages that last shared a common ancestor about 60 million years ago. This is one of the deepest hybridization events ever described and has important implications for plant speciation theory., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Background and Aims: Patterns of morphological evolution at levels above family rank remain underexplored in the ferns. The present study seeks to address this gap through analysis of 79 morphological characters for 81 taxa, including representatives of all ten families of eupolypod II ferns. Recent molecular phylogenetic studies demonstrate that the evolution of the large eupolypod II clade (which includes nearly one-third of extant fern species) features unexpected patterns. The traditional 'athyrioid' ferns are scattered across the phylogeny despite their apparent morphological cohesiveness, and mixed among these seemingly conservative taxa are morphologically dissimilar groups that lack any obvious features uniting them with their relatives. Maximum-likelihood and maximum-parsimony character optimizations are used to determine characters that unite the seemingly disparate groups, and to test whether the polyphyly of the traditional athyrioid ferns is due to evolutionary stasis (symplesiomorphy) or convergent evolution. The major events in eupolypod II character evolution are reviewed, and character and character state concepts are reappraised, as a basis for further inquiries into fern morphology., Methods: Characters were scored from the literature, live plants and herbarium specimens, and optimized using maximum-parsimony and maximum-likelihood, onto a highly supported topology derived from maximum-likelihood and Bayesian analysis of molecular data. Phylogenetic signal of characters were tested for using randomization methods and fitdiscrete., Key Results: The majority of character state changes within the eupolypod II phylogeny occur at the family level or above. Relative branch lengths for the morphological data resemble those from molecular data and fit an ancient rapid radiation model (long branches subtended by very short backbone internodes), with few characters uniting the morphologically disparate clades. The traditional athyrioid ferns were circumscribed based upon a combination of symplesiomorphic and homoplastic characters. Petiole vasculature consisting of two bundles is ancestral for eupolypods II and a synapomorphy for eupolypods II under deltran optimization. Sori restricted to one side of the vein defines the recently recognized clade comprising Rhachidosoraceae through Aspleniaceae, and sori present on both sides of the vein is a synapomorphy for the Athyriaceae sensu stricto. The results indicate that a chromosome base number of x =41 is synapomorphic for all eupolypods, a clade that includes over two-thirds of extant fern species., Conclusions: The integrated approach synthesizes morphological studies with current phylogenetic hypotheses and provides explicit statements of character evolution in the eupolypod II fern families. Strong character support is found for previously recognized clades, whereas few characters support previously unrecognized clades. Sorus position appears to be less complicated than previously hypothesized, and linear sori restricted to one side of the vein support the clade comprising Aspleniaceae, Diplaziopsidaceae, Hemidictyaceae and Rachidosoraceae - a lineage only recently identified. Despite x =41 being a frequent number among extant species, to our knowledge it has not previously been demonstrated as the ancestral state. This is the first synapomorphy proposed for the eupolypod clade, a lineage comprising 67 % of extant fern species. This study provides some of the first hypotheses of character evolution at the family level and above in light of recent phylogenetic results, and promotes further study in an area that remains open for original observation.

Premise of the Study:Until recently, most phylogenetic studies of ferns were based on chloroplast genes. Evolutionary inferences based on these data can be incomplete because the characters are from a single linkage group and are uniparentally inherited. These limitations are particularly acute in studies of hybridization, which is prevalent in ferns; fern hybrids are common and ferns are able to hybridize across highly diverged lineages, up to 60 million years since divergence in one documented case. However, it not yet clear what effect such hybridization has on fern evolution, in part due to a paucity of available biparentally inherited (nuclear-encoded) markers. Methods:We designed oligonucleotide baits to capture 25 targeted, low-copy nuclear markers from a sample of 24 species spanning extant fern diversity. Results:Most loci were successfully sequenced from most accessions. Although the baits were designed from exon (transcript) data, we successfully captured intron sequences that should be useful for more focused phylogenetic studies. We present phylogenetic analyses of the new target sequence capture data and integrate these into a previous transcript-based data set. Discussion:We make our bait sequences available to the community as a resource for further studies of fern phylogeny.

Premise: Bracken (Pteridium, Dennstaedtiaceae) is a cosmopolitan genus of aggressive disturbance colonizers that are toxic to agricultural livestock. The taxonomy of Pteridium has been treated in multiple schemes, ranging from one to six species worldwide, with numerous subspecies and varieties. Recent work has focused on the worldwide distribution and systematics of the bracken fern, but South America has been poorly represented. We present the first continent‐wide sampling and analysis of Pteridium esculentum, a Southern Hemisphere diploid species. Methods: Within South America, P. esculentum has several morphotypes, distinguished into subspecies by variation in indument and lamina architecture. We used double digest restriction site‐associated DNA sequencing (ddRADSeq) to assess the phylogenetic relationships of P. esculentum subspecies. Results: We found a striking genetic homogeneity in the species, being able to support only two morphotypes from molecular data: P. e. arachnoideum and P. e. campestre. We had high confidence for shallow and deep phylogenetic relationships, but less support for relationships among crown groups. Conclusions: We describe an east‐west geographic pattern that would explain the relationships between populations; and, in contrast to previous studies, we detected differences with P. esculentum from Australia. These results will lay the foundations for studying variations in this species' behavior as a weed, as well as its impact on the production of agricultural livestock in South America. [ABSTRACT FROM AUTHOR]

Hemiepiphytes have captured the attention of biologists since they seemingly hold clues to the evolution of epiphytes themselves. Hemiepiphytes are known to occur sporadically in the leptosporangiate ferns, but our understanding of their evolution remains limited by the relatively small number of detailed observations. This study adds to our knowledge by documenting seven species previously assumed to be holoepiphytes. This finding was based on fieldwork conducted in the Baining Mountains of Papua New Guinea that resulted in 319 collections representing 206 species. Approximately 3% of these species were hemiepiphytes: Asplenium acrobryum, A. amboinense, A. scandens, A. scolpendropsis, Crepidomanes aphlebioides, Leptochilus macrophyllus, and Sphaerostephanos scandens. All started growth as low-trunk epiphytes, and later, as larger climbing plants, exhibited strongly dimorphic roots consisting of short clasping ones that affixed the rhizome to the trunks and long feeding roots that entered the soil. Most of the seven hemiepiphyte species that we found exhibited distichous phyllotaxy and dorsiventrally flattened rhizomes, suggesting morphological convergence associated with this habit in four families. These new records suggest that large hemiepiphytic clades occur in Asplenium and Leptochilus. Our observations expand the geographic and taxonomic breadth of hemiepiphytic ferns, provide a baseline estimate of their diversity within a tropical flora, and offer morphological and phylogenetic clues to uncover additional records. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Antrophyum is one of the largest genera of vittarioid ferns (Pteridaceae) and is most diverse in tropical Asia and the Pacific Islands, but also occurs in temperate Asia, Australia, tropical Africa and the Malagasy region. The only monographic study of Antrophyum was published more than a century ago and a modern assessment of its diversity is lacking. Here, we reconstructed a comprehensively sampled and robustly supported phylogeny for the genus based on four chloroplast markers using Bayesian inference, maximum likelihood and maximum parsimony analyses. We then explored the evolution of the genus from the perspectives of morphology, systematics and historical biogeography. We investigated nine critical morphological characters using a morphometric approach and reconstructed their evolution on the phylogeny. We describe four new species and provide new insight into species delimitation. We currently recognize 34 species for the genus and provide a key to identify them. The results of biogeographical analysis suggest that the distribution of extant species is largely shaped by both ancient and recent dispersal events. [ABSTRACT FROM AUTHOR]

We undertook a molecular phylogenetic revision of hayscented ferns (Dennstaedtiaceae: Dennstaedtioideae) using four plastid markers. Our sampling represents ca. 40% of the extant diversity and includes the type species for each of the relevant segregate genera. We coded 18 discrete morphological characters which we used to find diagnosable clades. We show that Dennstaedtia is polyphyletic, with the majority of species forming three morphologically distinct clades, but its type (D. flaccida) is nested within Microlepia. As such, we support the conservation of Dennstaedtia with a new type, D. dissecta. Following our results, we develop a classification of four genera: Dennstaedtia, Microlepia, Mucura (gen. nov.) and Sitobolium. Beyond the inclusion of D. flaccida, we propose to maintain Microlepia with its current circumscription. Except for a single adventive species in the Neotropics, Microlepia is a Paleotropical genus of about 60 species diagnosed by their distinctive perispore ornamentation of rodlets, and by petioles that lack epipetiolar buds. Mucura is a Neotropical genus of two species that differ from all other Dennstaedtiaceae by the combination of dichotomously branching rhizomes, petioles that lack epipetiolar buds, marginal sori with both abaxial and adaxial indusia, and trilete spores with a unique perispore ornamentation. As defined here, Dennstaedtia is a pantropical genus of about 55 species recognized by having unbranched rhizomes, petioles bearing epipetiolar buds, and by often bearing proliferous buds upon the leaves. Sitobolium is a small clade of ca. five species distinguished by their relatively small leaves that have elongate catenate hairs. These hairs often bear a capitate non‐glandular terminal cell. In support of our classification, we provide a key to the eleven genera of Dennstaedtiaceae, and for the four genera of Dennstaedtioideae we provide morphological and geographic synopses, a list of constituent species, and necessary new combinations. [ABSTRACT FROM AUTHOR]

Background and Aims Ferns are the second largest group of vascular plants and are distributed nearly worldwide. Although ferns have been integrated into some comparative ecological studies focusing on hydathodes, there is a considerable gap in our understanding of the functional anatomy of these secretory tissues that are found on the vein endings of many fern leaves. In this study, we aimed to investigate the phylogenetic distribution, structure and function of fern hydathodes. Methods We performed a global review on fern hydathodes and their phylogenetic distribution, carried out an ancestral character state reconstruction, and studied the structure, guttation and elemental composition of salt residues of eight species, and the diurnal patterns of xylem pressure of two species. Key Results Hydathodes are known from 1189 fern species, 92 genera and 19 families of 2 orders, Equisetales and Polypodiales. Stochastic character mapping indicated multiple gains and losses of hydathodes at the genus level, occurring especially during the last 50 million years of fern evolution. Hydathodes were located on the adaxial leaf surface and characterized by a cytoplasm-rich, pore-free epidermis, and became functional for several weeks after nearly complete leaf expansion. In two species, positive xylem pressure built up at night, potentially facilitating guttation. Guttation fluid was rich in Ca and often Si, but also contained P, Mg, Na and Al. Conclusions Stochastic character mapping and the structural and functional diversity of hydathodes indicate multiple origins, and their presence/absence in closely related taxa implies secondary losses during fern evolution. Positive xylem pressure and high air humidity play an important role as drivers of guttation. Hydathodes may contribute to the regulation of leaf nutrient stoichiometry by the release of excessive compounds and minerals other than waste products, but the presence of essential chemical elements in salt residues also indicates possible leakage. [ABSTRACT FROM AUTHOR]

Sporangiasters are an uncommon type of paraphyses, occurring in a handful of leptosporangiate fern genera. We report sporangiasters in Parablechnum nesophilum, which is their first recorded occurrence in the Blechnaceae. We provide evidence of their homology to sporangia and discuss their functional significance. The presence of sporangiasters in P. nesophilum is surprising because the species has a well-developed indusium, and paraphyses are generally most common in exindusiate ferns. We surmise that these sporangiasters act as a second stage of protection for the developing sporangia after the indusium retracts. Alternatively, it is possible that sporangiasters may influence the vagility of spores by inhibiting dehiscence and limiting the ability of the annulus to disperse its spores. [ABSTRACT FROM AUTHOR]

Aim: It is well known that the distribution of species diversity is spatially heterogeneous, but understanding the factors contributing to this heterogeneity and to the formation of biodiversity hotspots remains a challenge. Here, we seek to improve our understanding of how historical, ecological and evolutionary processes contribute to current patterns of global fern diversity. Location: Worldwide. Taxon: Ferns. Methods: To evaluate the drivers of global fern diversity, we integrate over 800,000 georeferenced species occurrence records of nearly 8000 species, a time‐calibrated phylogeny and seven climate and environmental layers. We use these data to summarize diversity and evolutionary patterns at a resolution of 100 × 100 km, and identify hotspots of fern species richness and endemism. We compare these hotspots to neighbouring non‐hotspot regions to provide insight into the factors controlling global patterns of fern diversity. Results: Tropical and subtropical mountains harbour a disproportionate amount of species relative to the land area they occupy; 58% of global species richness occur in eight principally montane hotspots together comprising just 7% of Earth's land area. We identify hotspots of fern species richness and endemism that are universally characterized by disproportionately high ecological variation. We demonstrate that total fern species richness scales linearly with available climate space at regional and global scales. Main Conclusions: Areas of high environmental heterogeneity harbour a disproportionate amount of fern species, and global patterns of extant fern diversity reflect the distribution of these areas, especially in mountains at lower latitudes. Persistence of ancient lineages in areas with long‐term climatic stability helps explain exceptional endemism in regions such as Malesia. [ABSTRACT FROM AUTHOR]

To mark the commencement of his retirement as Nathaniel Lord Britton Curator of Botany, and appointment as Curator Emeritus at the New York Botanical Garden, we pay tribute to Robbin Moran and impact on the botanical community with a brief synopsis of his career. Naturalist, fern expert, adored teacher—it is difficult to adequately pay tribute to his accomplishments, and his impact on botany in a single article. Robbin has published four books, 13 monographs of neotropical fern clades, over 170 scientific papers, and dozens of popular articles. He has named 115 new species, five new genera, and one family of ferns. He is eponymized by seven new species and the genus Moranopteris. We recount his earliest days and academic trajectory to become a leading researcher and educator in pteridology. We highlight his major influences, scientific accomplishments, and outreach to the botanical community. [ABSTRACT FROM AUTHOR]

Family- and genus-level circumscription of ferns in the suborder Aspleniineae (eupolypods II) has long been controversial, due in part to confusion about the relationship among the families Aspleniaceae and Athyriaceae. Recent studies have demonstrated that character states traditionally used to infer a close relationship between these two families are either symplesiomorphic or homoplastic, and re-examination of numerous taxa has led to the recircumscription of several clades, and the description of several new families and genera. In light of these findings, we re-evaluated the taxonomic affinities of Diplazium praestans, a little-known fern from western Amazonia that is morphologically disparate to the remainder of Neotropical Diplazium. Using sequence data from three chloroplast markers and analysis of eight morphological characters, we demonstrate that Diplazium praestans was erroneously placed in that genus and instead is a Hymenasplenium. We place it in a phylogenetic context, reassess its morphology in light of our findings, evaluate its conservation status under IUCN criteria, and provide a new combination: Hymenasplenium praestans. We also provide an updated key to the Neotropical species of Hymenasplenium and discuss unresolved taxonomic problems in the genus. [ABSTRACT FROM AUTHOR]

The article presents an update on the taxonomic distribution of chlorophyllous spores in ferns as of April 2021. Other topics include the characteristics of the achlorophyllous non-green spores of ferns, the species with chlorophyllous spores like Lomaria nuda Willd (Blechnaceae), Platycerium wallichii Hook. (Polypodiaceae), and Pleopeltis wiesbaurii (Sodiro) Lellinger, and the life span differences of chlorophyllous and achlorophyllous spores in ferns.

Almost fifty years ago Dr. Rolla M. Tryon investigated the patterns of neotropical fern diversity and discovered that sites of exceptional richness and endemism are found in five predominantly montane regions. Here, we revisit these sites with the aid of contemporary methodologies. We integrate phylogenetic, ecological, climatic, and occurrence data to better understand what factors contribute to the patterns of fern diversity throughout the neotropics. With this dataset we are able to reassess Tryon's neotropical hotspots fifty years later and take one step closer to understanding the processes governing the distribution of fern species. We recover six hotspots of neotropical species richness and endemism that closely mirror those delineated by Tryon. Like Tryon, we find that hotspots are found predominantly in montane regions with more climatic space compared to surrounding areas. Patterns of species richness and lineage diversification can largely be explained by the extent of available habitats, especially in association with montane ecosystems. We also show that patterns of species assemblages across the neotropics are largely dictated by distance and elevation. In synthesis, we propose that, in addition to migration and persistence of relictual lineages, patterns of species richness and endemism in the neotropics are driven by in situ speciation in montane regions. [ABSTRACT FROM AUTHOR]

Premise of research. Spores and pollen often exhibit distinctive morphology, resulting from the structure of the exine (spore wall), and elaborate external ornamentation, known as perine. Spore-dispersed plants, particularly ferns, exhibit remarkable variation in the surface structure of their spores and provide an excellent model for the study of morphological trait evolution. Our goal is to assess the utility of spore morphology for characterizing clades and taxa. For this study, we chose Thelypteridaceae, a family of ferns with over 1000 species and exceptionally diverse spore morphology. Methodology. We generated a 200-species molecular phylogeny representing family diversity. We assigned discrete states for seven morphological characters of spores based on images from scanning electron microscopy (SEM). We then optimized these seven characters and their states on our molecular phylogeny, which represented about 10% of the species diversity in the family, including members of all 27 currently recognized genera, with the exception of the monotypic Menisorus and Nannothelypteris , which includes three species. We quantify phylogenetic signal and homoplasy for morphological traits and test for pairwise correlated evolution of traits. Finally, we provide a synoptic description of spore morphology for genera in the family, synthesizing our current findings with previous work. Pivotal results. Reticulate perine and perforate perine, which show high phylogenetic signal and low homoplasy, characterized genera and major clades. Microstructure, or fine superficial sculpturing, was not synapomorphic for any group and varied at fine phylogenetic scales. Certain genera, such as Amauropelta and Stegnogramma , exhibit uniform morphology among their species, whereas others, such as Christella , are highly variable. Our phylogenetic analyses indicate that Christella and Pronephrium are nonmonophyletic, whereas infrageneric sections of these genera are largely corroborated. Conclusions. Characters pertaining to perine macrostructure and perforations, in particular, were reconstructed as synapomorphic for genera or sections in the Thelypteridaceae. High variability of perine characters within the christelloid clade suggests that it is a promising group on which to focus further sampling. Our approach provides explicit statements of character evolution for perine morphology that can be used as a framework for further studies. We demonstrated that the repository of high-quality SEM images of spores in the literature serves as a rich source of morphological data. [ABSTRACT FROM AUTHOR]

We carried out a molecular phylogenetic analysis of Neotropical lady ferns (Athyrium s.str. and Anisocampium) using five plastid markers. We found two major results. First, three Neotropical species (Anisocampium skinneri, Athyrium palmense, A. tejeroi) formed a clade, and this clade was sister to the rest of Athyrium. The three members of this clade differ from Athyrium s.l. by creeping rhizomes with internodes 1–2 mm long, and rhizome apices that protrude beyond the current season's cluster of leaves. Also, the leaves are distichously arranged, lack trophopods, have petiole bases broadly U‐shaped in transverse section, and bear thin, membranous laminae. We recognize this clade as a new genus, Ephemeropteris, and provide three new combinations: E. palmensis, E. skinneri, and E. tejeroi. The name of the new genus is derived from the seasonal production of its leaves, which are produced during the wet season and die back (i.e., are ephemeral) at the beginning of the dry season. Ephemeropteris is largely restricted to the Pacific side of Central America, a region that exhibits a marked dry season from November to May. We provide a key to the seven genera (including Ephemeropteris) we now recognize in the Athyriaceae, and a taxonomic treatment of the three species of Ephemeropteris. The treatment includes descriptions, illustrations, nomenclatural data, specimens cited, and a dot‐distribution map. Our second major result from the phylogenetic analysis is that the remaining three Neotropical species of Athyrium s.str. are polyphyletic. One of our seven samples was resolved in the A. filix‐femina clade (sect. Athyrium), to which all species of Neotropical Athyrium were previously assumed to belong to. Our six other samples of Neotropical Athyrium were resolved in A. sect. Mackinnoniana, previously construed as entirely Asian. [ABSTRACT FROM AUTHOR]

The relationship of Hypolepis brooksiae , H. nigrescens , and H. scabristipes to the remainder of Hypolepis (Dennstaedtiaceae) has been questioned by previous authors based on their unique combination of morphological characters and different base chromosome number. Using four chloroplast genes including rbcL , atpA , rpL6 , and rps4 - trnS intergenic spacer (IGS) from 32 samples, representing 24 species of Dennstaedtiaceae, we recovered a clade comprising H. brooksiae and H. nigrescens , distinct from the remaining species of Hypolepis . This clade is resolved as sister to the clade comprising Blotiella , Paesia and Histiopteris . We reconstructed ancestral states of 16 morphological characters and found that this clade is distinguished by indeterminate, scandent leaves exhibiting rhythmic growth, provided with recurved black-tipped prickles, and stipule-like pinnules that protect the emerging crosier and pinnae departures, rachis-costa architecture where the adaxial sulcus is confluent with the next lower order, and a base chromosome number of x = 29. In light of this molecular and morphological evidence, we describe a new genus, Hiya , and provide nomenclatural combinations to accommodate the three known species segregated from Hypolepis : Hiya brooksiae , Hiya nigrescens , and Hiya scabristipes . [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY:: This paper investigates the occurrence and evolution of aluminum (Al) accumulation within ferns and lycophytes, which is characterized by Al concentrations above 1000 mg·kg−1 in aboveground plant tissues. We hypothesize that this feature is more common in ferns than in angiosperms, and potentially correlated with growth form and other chemical elements. METHODS:: Aluminum concentrations were obtained from novel analyses and literature for a total of 354 specimens and 307 species. Moreover, a semiquantitative aluminon test was applied for a subset of 105 species and validated against exact Al measurements. KEY RESULTS:: Molecular phylogenetic analyses showed that the major Al‐accumulating groups were primarily found in the Gleicheniales and Cyatheales, and largely absent in the Polypodiales. At the species and generic level, Al accumulation was typically either absent or present, and mixed results within a single species and genus were limited to less than 30% of the species and genera tested. Epiphytic ferns had significantly lower Al levels than terrestrial ferns, although this finding was not significant after phylogenetic correction. In addition, a significant, positive correlation was found between Al and iron, while Al was negatively correlated with phosphorus and potassium concentrations. CONCLUSIONS:: Aluminum accumulation is most common outside of the Polypodiales and occurs in 38% of the species studied, indicating that this trait is indeed common within subtropical and tropical ferns, a finding that could be in line with their role as pioneer species on landslides and soils with high levels of soluble Al. [ABSTRACT FROM AUTHOR]

Ferns are the second-most diverse lineage of vascular plants on Earth, yet the best-sampled time-calibrated phylogeny of the group to date includes fewer than 5% of global diversity and was published seven years ago. We present a time-calibrated phylogeny that includes nearly half of extant fern diversity. Our results are evaluated in the context of previous studies and the fossil record, and we develop new hypotheses about the radiation of leptosporangiate ferns. We used sequence data from six chloroplast regions for nearly 4000 species of ferns to generate the most comprehensive phylogeny of the group ever published. We calibrate the phylogeny with twenty-six fossils and use an array of phylogenetic methods to resolve phylogenetic relationships, estimate divergence times, and infer speciation, extinction, and net diversification rates. We infer a mid-late Silurian origin for ferns (including horsetails) and an early Carboniferous origin for leptosporangiate ferns. Most derived fern families appeared in the Cretaceous and persisted for millions of years before rapidly diversifying in the Cenozoic. We find no evidence of differential rates of diversification among terrestrial and epiphytic species. Our findings challenge previous hypotheses on the evolutionary history of ferns and present a new paradigm for their Cenozoic radiation. We estimate earlier divergences for most fern lineages than were reported in previous studies and provide evidence of extended persistence of major fern lineages prior to rapid diversification in the last fifty million years. [ABSTRACT FROM AUTHOR]