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The complete chloroplast genome sequence of Crepidomanes latealatum (Bosch) Copel. was determined in the present study. The genome is 145,943 base pairs (bp) in length and comprised two inverted repeats (32,990 bp) between a large single copy (92,170 bp) and a small single copy (20,783 bp). It contains 88 coding genes, 8 rRNA genes, 34 tRNA genes, and 1 pseudogene of trnL-UAA, and the GC content is 37.6%. Molecular phylogenetic analysis based on the plastid genome sequences of related taxa strongly supported the monophyly of the family Hymenophyllaceae, and the genus Vandenboschia was a sister group of Crepidomanes. In addition, compared to C. minutum, two large deletions of 453 bp and 878 bp were found in the IGS regions of petA-psbI and rrn16-trnV-GAC of C. latealatum cp genome, respectively.

The complete chloroplast genome sequence of Crepidomanes latealatum (Bosch) Copel. was determined in the present study. The genome is 145,943 base pairs (bp) in length and comprised two inverted repeats (32,990 bp) between a large single copy (92,170 bp) and a small single copy (20,783 bp). It contains 88 coding genes, 8 rRNA genes, 34 tRNA genes, and 1 pseudogene of trnL-UAA, and the GC content is 37.6%. Molecular phylogenetic analysis based on the plastid genome sequences of related taxa strongly supported the monophyly of the family Hymenophyllaceae, and the genus Vandenboschia was a sister group of Crepidomanes. In addition, compared to C. minutum, two large deletions of 453 bp and 878 bp were found in the IGS regions of petA-psbI and rrn16-trnV-GAC of C. latealatum cp genome, respectively. [ABSTRACT FROM AUTHOR]

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Didymoglossum krausii (Hymenophyllaceae), Amauropelta jujuyensis and Amauropelta nubicola (Thelypteridaceae) are recorded for the first time in Tucumán, Argentina, in Yungas biogeographic province. This is the southernmost record of the three taxa. An updated description is provided, along with pictures, and characteristic of the habitats of the species in Tucumán.

Premise: Reinvestigation of previously described fossil plants using improved techniques can provide insights for additional characters resulting in better family assignments and relationships to modern plants, as in this new study of the fossil fern Acrostichopteris from the mid‐Cretaceous. The discovery of new species within genera provides additional characteristics for comparisons and support for family assignments. Methods: Fossil material was uncovered from the matrix (degagement) for the specimens described here. Material was removed from the matrix and mounted for examination by scanning electron microscopy (SEM). Spores were extracted and prepared for examination with light, fluorescence, and SEM. Characters for the previously described material from the Potomac Group in the USA and the new material from Spain were compared with those of other fossils assigned to the genus. Results: The genus, described by Fontaine in 1889, reexamined by Berry in 1911, and assigned to the Schizaeaceae by Reed in 1947, is reassigned to the family Hymenophyllaceae on the basis of characteristics of the pinnules, sori, sporangia, and spores. We describe a new species in the genus from the Lower Cretaceous (Albian) of Spain that most likely belongs in this family, based on characteristics of the pinnules and the sori. A summary of all the species previously assigned to the genus is included. Conclusions: Assignment of this fossil to the family Hymenophyllaceae is based on all characters known and comparison to modern species, provides the time for appearance of characteristics within the family, and indicates diversification of Hymenophyllum species in the mid‐Cretaceous. [ABSTRACT FROM AUTHOR]

During a botanical exploration in the Los Ruiles National Reserve (Chile), a population of Hymenophyllum caudatum Bosch was identified. Fronds were found at the base of a rock, under a hygrophilous vegetation cover, in a ravine (35°49'56.49"S -72°30'42.44"W). The finding in this wilderness area extends the distribution by 120 km northwards on the mainland, which until now was limited to the coastal area of the city of Concepción (36°47'07.86"). This contribution presents an observed specimen, the site of the find and the accompanying species. [ABSTRACT FROM AUTHOR]

Abstract Background Filmy-ferns (Hymenophyllaceae) are poikilohydric, homoiochlorophyllous desiccation-tolerant (DT) epiphytes. They can colonize lower and upper canopy environments of humid forest. Filmy-ferns desiccate rapidly (hours), contrasting with DT angiosperms (days/weeks). It has been proposed that desiccation tolerance in filmy-ferns would be associated mainly with constitutive features rather than induced responses during dehydration. However, we hypothesize that the inter-specific differences in vertical distribution would be associated with different dynamics of gene expression within the dehydration or rehydration phases. A comparative transcriptomic analysis with an artificial neural network was done on Hymenophyllum caudiculatum (restricted to lower canopy) and Hymenophyllum dentatum (reach upper canopy) during a desiccation/rehydration cycle. Results Raw reads were assembled into 69,599 transcripts for H. dentatum and 34,726 transcripts for H. caudiculatum. Few transcripts showed significant changes in differential expression (DE). H. caudiculatum had ca. twice DE genes than H. dentatum and higher proportion of increased-and-decreased abundance of genes occurs during dehydration. In contrast, the abundance of genes in H. dentatum decreased significantly when transitioning from dehydration to rehydration. According to the artificial neural network results, H. caudiculatum enhanced osmotic responses and phenylpropanoid related pathways, whilst H. dentatum enhanced its defense system responses and protection against high light stress. Conclusions Our findings provide a deeper understanding of the mechanisms underlying the desiccation tolerance responses of two filmy ferns and the relationship between the species-specific response and the microhabitats these ferns occupy in nature.

Premise of research. Newly recognized compression fossils of fertile leptosporangiate ferns assignable to Dennstaedtia Bernh. (Dennstaedtiaceae) and Hymenophyllum Sm. (Hymenophyllaceae) are described from the latest early Eocene floras of the Okanogan Highlands, British Columbia, Canada, and northeastern Washington. Methodology. Specimens were photographed with reflected light microscopy and were studied morphologically in comparison with related fossil and extant forms. Focus-shift stacking was used to layer photos of some specimens. Some were photographed with polarized light. The holotype specimen of Dennstaedtia christophelii sp. nov. was also studied with environmental scanning electron microscopy. Pivotal results. We describe D. christophelii sp. nov. (Dennstaedtiaceae) and Hymenophyllum axsmithii sp. nov. (Hymenophyllaceae) on the basis of vegetative and fertile remains of fragmentary fronds. Specimens of D. christophelii are one-pinnate-pinnatifid to bipinnate and bear frequent marginal round sori in cuplike indusia on small crenulate to dissected pinnae. Sporangia each have a prominent annulus with approximately six to eight long cells visible. Hymenophyllum axsmithii has the type of lamina cutting, sorus position, alate rachis, sorus shape, and venation corresponding to Hymenophyllum , subgenus Sphaerocionium (Hymenophyllaceae). The numerous sporangia per sori each bear a prominent annulus, and 7–10 casts of spores are noted in some sporangia. Conclusions. These fossils document the occurrence of leptosporangiate fern diversity in the early Eocene Okanogan Highlands floras. Dennstaedtia christophelii represents one of several occurrences of Dennstaedtiaceae in the Eocene. Hymenophyllum axsmithii is the first unequivocal member of Hymenophyllaceae to be reported from these diverse plant and insect assemblages from lacustrine and swamp settings under warm temperate climates of the latest early Eocene. [ABSTRACT FROM AUTHOR]

Desiccation tolerance was a key trait that allowed plants to colonize land. However, little is known about the transition from desiccation tolerant non-vascular plants to desiccation sensitive vascular ones. Filmy ferns (Hymenophyllaceae) represent a useful system to investigate how water-stress strategies differ between non-vascular and vascular stages within a single organism because they have vascularized sporophytes and nonvascular gametophytes that are each capable of varying degrees of desiccation tolerance. To explore this, we surveyed sporophytes and gametophytes of 19 species (22 taxa including varieties) of filmy ferns on Moorea (French Polynesia) and used chlorophyll fluorescence to measure desiccation tolerance and light responses. We conducted phylogenetically informed analyses to identify differences in physiology between life stages and growth habits. Gametophytes had similar or less desiccation tolerance (ability to recover from 2 days desiccation at − 86 MPa) and lower photosynthetic optima (maximum electron transport rate of photosystem II and light level at 95% of that rate) than sporophytes. Epiphytes were more tolerant of desiccation than terrestrial species in both life stages. Despite their lack of greater physiological tolerances, gametophytes of several species occurred over a wider elevational range than conspecific sporophytes. Our results demonstrate that filmy fern gametophytes and sporophytes differ in their physiology and niche requirements, and point to the importance of microhabitat in shaping the evolution of water-use strategies in vascular plants. [ABSTRACT FROM AUTHOR]

The inventory of the Cuban lycophytes and ferns, and for each of the 605 taxa, their correct name and the synonymy used, as well as the distribution per provinces and their state of conservation are presented. The best represented families are Dryopteridaceae, Pteridaceae, Thelypteridaceae, Polypodiaceae and Hymenophyllaceae. The highest concentration of taxa occurs in the eastern provinces, which include the most prominent mountain systems. A total of 92 endemic taxa are considered, which represents 15.2 % of those present in Cuba. The greatest floristic affinity relationships are established with Hispaniola and Jamaica, the high endemism of pteridophytes being notable for the Greater Antilles. The values of threatened species proposed per categories are 215 Critically Endangered, 105 Endangered and 24 Vulnerable. [ABSTRACT FROM AUTHOR]

Hymenoglossum cruentum (Hymenophyllaceae) is a poikilohydric, homoiochlorophyllous desiccation-tolerant (DT) epiphyte fern. It can undergo fast and frequent dehydration-rehydration cycles. This fern is highly abundant at high-humidity/low-light microenvironments within the canopy, although rapid changes in humidity and light intensity are frequent. The objective of this research is to identify genes associated to desiccation-rehydration cycle in the transcriptome of H. cruentum to better understand the genetic dynamics behind its desiccation tolerance mechanism. H. cruentum plants were subjected to a 7 days long desiccation-rehydration process and then used to identify key expressed genes associated to its capacity to dehydrate and rehydrate. The relative water content (RWC) and maximum quantum efficiency (Fv/Fm) of H. cruentum fronds decayed to 6% and 0.04, respectively, at the end of the desiccation stage. After re-watering, the fern showed a rapid recovery of RWC and Fv/Fm (ca. 73% and 0.8, respectively). Based on clustering and network analysis, our results reveal key genes, such as UBA/TS-N, DYNLL, and LHC, orchestrating intracellular motility and photosynthetic metabolism; strong balance between avoiding cell death and defense (CAT3, AP2/ERF) when dehydrated, and detoxifying pathways and stabilization of photosystems (GST, CAB2, and ELIP9) during rehydration. Here we provide novel insights into the genetic dynamics behind the desiccation tolerance mechanism of H. cruentum.

In this study, four plastomes of Hymenophyllum, distributed in the Korean peninsula, were newly sequenced and phylogenomic analysis was conducted to reveal (1) the evolutionary history of plastomes of early-diverging fern species at the species level, (2) the importance of mobile open reading frames in the genus, and (3) plastome sequence divergence providing support for H. coreanum to be recognized as an independent species distinct from H. polyanthos. In addition, 1C-values of H. polyanthos and H. coreanum were measured to compare the genome size of both species and to confirm the diversification between them. The rrn16-trnV intergenic regions in the genus varied in length caused by Mobile Open Reading Frames in Fern Organelles (MORFFO). We investigated enlarged noncoding regions containing MORFFO throughout the fern plastomes and found that they were strongly associated with tRNA genes or palindromic elements. Sequence identity between plastomes of H. polyanthos and H. coreanum is quite low at 93.35% in the whole sequence and 98.13% even if the variation in trnV-rrn16 intergenic spacer was ignored. In addition, different genome sizes were found for these species based on the 1C-value. Consequently, there is no reason to consider them as a conspecies. [ABSTRACT FROM AUTHOR]

Hymenoglossum cruentum (Hymenophyllaceae) is a poikilohydric, homoiochlorophyllous desiccation-tolerant (DT) epiphyte fern. It can undergo fast and frequent dehydration-rehydration cycles. This fern is highly abundant at high-humidity/low-light microenvironments within the canopy, although rapid changes in humidity and light intensity are frequent. The objective of this research is to identify genes associated to desiccation-rehydration cycle in the transcriptome of H. cruentum to better understand the genetic dynamics behind its desiccation tolerance mechanism. H. cruentum plants were subjected to a 7 days long desiccation-rehydration process and then used to identify key expressed genes associated to its capacity to dehydrate and rehydrate. The relative water content (RWC) and maximum quantum efficiency (F v/ F m) of H. cruentum fronds decayed to 6% and 0.04, respectively, at the end of the desiccation stage. After re-watering, the fern showed a rapid recovery of RWC and F v/ F m (ca. 73% and 0.8, respectively). Based on clustering and network analysis, our results reveal key genes, such as UBA/TS-N , DYNLL , and LHC , orchestrating intracellular motility and photosynthetic metabolism; strong balance between avoiding cell death and defense (CAT3 , AP2/ERF) when dehydrated, and detoxifying pathways and stabilization of photosystems (GST , CAB2 , and ELIP9) during rehydration. Here we provide novel insights into the genetic dynamics behind the desiccation tolerance mechanism of H. cruentum. [ABSTRACT FROM AUTHOR]

Background: Filmy-ferns (Hymenophyllaceae) are poikilohydric, homoiochlorophyllous desiccation-tolerant (DT) epiphytes. They can colonize lower and upper canopy environments of humid forest. Filmy-ferns desiccate rapidly (hours), contrasting with DT angiosperms (days/weeks). It has been proposed that desiccation tolerance in filmy-ferns would be associated mainly with constitutive features rather than induced responses during dehydration. However, we hypothesize that the inter-specific differences in vertical distribution would be associated with different dynamics of gene expression within the dehydration or rehydration phases. A comparative transcriptomic analysis with an artificial neural network was done on Hymenophyllum caudiculatum (restricted to lower canopy) and Hymenophyllum dentatum (reach upper canopy) during a desiccation/rehydration cycle. Results: Raw reads were assembled into 69,599 transcripts for H. dentatum and 34,726 transcripts for H. caudiculatum. Few transcripts showed significant changes in differential expression (DE). H. caudiculatum had ca. twice DE genes than H. dentatum and higher proportion of increased-and-decreased abundance of genes occurs during dehydration. In contrast, the abundance of genes in H. dentatum decreased significantly when transitioning from dehydration to rehydration. According to the artificial neural network results, H. caudiculatum enhanced osmotic responses and phenylpropanoid related pathways, whilst H. dentatum enhanced its defense system responses and protection against high light stress. Conclusions: Our findings provide a deeper understanding of the mechanisms underlying the desiccation tolerance responses of two filmy ferns and the relationship between the species-specific response and the microhabitats these ferns occupy in nature. [ABSTRACT FROM AUTHOR]

The ferns family Hymenophyllaceae is one of the most interesting basal clades of ferns, which is widely distributed in tropical and subtropical regions, less common in temperate latitudes of both hemispheres. This work deals with the taxonomic study of the representatives of the subfamily Trichomanoideae, which according to the classification of PPG 1 (2016) in the region are represented only by three genera. Following the style of the treatment of the genus Hymenophyllum, this paper is the second report of our studies of the filmy ferns from the Pan-Himalaya which is a part of the ongoing “Flora of Pan-Himalaya” project. In the present account, the taxonomy of three genera of Hymenophyllaceae: Crepidomanes, Didymoglossum, and Vandenboschia from the Pan-Himalaya are carefully revised based on morphological characters and recent works in the region. Herbarium materials kept in the National Herbarium (PE) have been fully studied and compared with collections from the Himalayas kept in European herbaria (K, BM, E). The generic and infrageneric classifications follow those of Ebihara et al. (2006) which recognized only nine genera. In the Himalayas, only four genera represented, i. e., Hymenophyllum (10 species), Crepidomanes (5 species), Didymoglossum (1 species), and Vandenboschia (2 species). The synopsis includes a key for species identification, standard taxonomic citations for the genus, sections, species. For each taxon as well as of each synonym are verified and indicated, necessary literature citation, morphology descriprion and citation of the reprehensive specimens from the Pan-Himalaya are recorded, overall distribution is mentioned and distribution in the Flora of Pan-Himalaya area is mapped. Although this is only a precursor of the ongoing “Flora of Pan-Himalaya” project, it is useful for identification of new collections from the area, and provides basic information for the conservation and ecological studies of the filmy ferns from the Himalayas, a very sensitive area to global changes. Crepidomanes parvifolium and Didymoglossum sublimbatum in this region are critical endangered concerning their small populations and limited distribution.

Ferns present an interesting case in island biogeography because of their unusually high dispersal ability. A general survey of the filmy ferns (Hymenophyllaceae) of Moorea, French Polynesia was undertaken by observing distribution in the field, conducting tests of desiccation tolerance, and inferring a phylogeny based on morphological characters. A total of 12 filmy fern species (including three species previously unreported in the literature for Moorea) were found to occur in moist, wellcovered habitats throughout the island, with distinct sets of high elevation and low elevation species. Five species were included in an experiment to determine relative degree of desiccation tolerance; results indicate that terrestrial species have lower desiccation tolerance than epiphytic or epipetric species. In order to place the Moorea filmy ferns in the larger archipelago context, eight additional Society Island species were included in the phylogeny for a total of 20 taxa based on 21 morphological characters; interspecies relationships reflect the taxonomy of Hymenophyllaceae sensu lato. Filmy fern species are widely dispersed throughout the Society Islands, and there is no indication of an adaptive radiation on Moorea.

Hymenophyllum subg. Mecodium (Hymenophyllaceae) is represented by ca. 35 epiphytic species. Past reports suggest that Hymenophyllum polyanthos (Sw.) Sw., a pantropical species, does not represent a monophyletic grouping as it is recognized today. This research focuses on the H. polyanthos species complex, while comparing it to other species of subg. Mecodium using molecular and morphological traits. Here, chloroplast gene sequences of the atpB, atpB–rbcL–accD, rps4–trnS, and matK regions of 132 samples are compared under phylogenetic analyses and the resulting trees are discussed according to distributional and morphological differences. As a result, two big clades can be observed within Mecodium: one represented by plants distributed through Malesia, Australia, Pacific islands, Indian Ocean, and southern South America, and the other represented by plants occurring in Central and South America, Africa, and Asia. Hymenophyllum polyanthos samples appear interspersed in the phylogeny, evidencing its polyphyletic status. Main lineages identified here as H. polyanthos include: (1) plants from the Neotropics, closely related to species like H. myriocarpum Hook. and H. undulatum Sw., and probably representative of the type lineage for the species; (2) several independent lineages within the Asian samples; and (3) two distinct lineages distributed from Malesia and Pacific regions to South and Central America. The combination of distributional patterns and a morphological analysis of seven leaf traits suggests that these lineages are mostly sympatric and show a morphological variation that overlaps with each other. [ABSTRACT FROM AUTHOR]

The Early Jurassic flora of the Mecsek Mountains is diverse, with numerous representatives of ferns, seed ferns, cycadophytes, ginkgophytes, and conifers. Its (para-)autochthonous deposition, good preservation and low collection bias has permitted researchers to save delicate, small plant remains that would generally be missing from the fossil record. These plant fossils are characterized by having a "filmy" (probably unilayered) structure, thin stalks with flat leaf-like branches and ultimate irregular segments with streamlined epidermal cells having thick cell walls. Due to the absence of sporangia, the plant remains cannot be confidently assigned to any higher plant group, although they show some similarities to thalloid liverworts with raised vegetative bodies and also have some resemblance to the fern family Hymenophyllaceae. The new genus and species Leonophyllum tenellum Barbacka et Kustatscher is erected. [ABSTRACT FROM AUTHOR]

Identifications are given for 713 specimens of Hymenophyllaceae collected on Ambon and Seram islands, the Moluccas, Indonesia, during 1983-86. The collection is composed of forty-seven species and one variety belonging to seven genera. The dataset is deposited in GBIF and available at https://www.gbif.jp/ipt/resource?r=seram_hymen. [ABSTRACT FROM AUTHOR]

The Malesian species Hymenophyllum reinwardtii is reported as a new record for Australia. This distinctive filmy fern can be recognized by the undulate and dentate lamina margins, the undulate and dentate rachis wing, and the circular indusial flaps whose margins are usually irregularly and sparsely denticulate or rarely entire. The species was collected in the vicinity of the summit of Mt Finnigan in June 2017, and is currently known in Australia by this one gathering. [ABSTRACT FROM AUTHOR]

Premise of the Study: Filmy ferns (Hymenophyllales) are a highly specialized lineage, having mesophyll one‐cell layer thick and inhabiting particularly shaded and humid environments. The phylogenetic placement of Hymenophyllales has been inconclusive, and while over 87 whole fern plastomes have been published, none was from Hymenophyllales. To better understand the evolutionary history of filmy ferns, we sequenced the first complete plastome for this order. Methods: We compiled a phylogenomic plastome data set encompassing all 11 fern orders, and reconstructed phylogenies using different data types (nucleotides, codons, and amino acids) and partition schemes (codon positions and loci). To infer the evolution of fern plastome organization, we coded plastome features, including inversions, inverted repeat boundary shifts, gene losses, and tRNA anticodon sequences as characters, and reconstructed the ancestral states for these characters. Key Results: We discovered a suite of novel, Hymenophyllales‐specific plastome structures that likely resulted from repeated expansions and contractions of the inverted repeat regions. Our phylogenetic analyses reveal that Hymenophyllales is highly supported as either sister to Gleicheniales or to Gleicheniales + the remaining non‐Osmundales leptosporangiates, depending on the data type and partition scheme. Conclusions: Although our analyses could not confidently resolve the phylogenetic position of Hymenophyalles, the results here highlight the danger of drawing conclusions from “all‐in” phylogenomic data set without exploring potential inconsistencies in the data. Finally, our first order‐level reconstruction of fern plastome structural evolution provides a useful framework for future plastome research. [ABSTRACT FROM AUTHOR]

The Middle Jurassic deposits of the Shemshak Group and Hojedk Formation are widespread in north, central, and central east Iran. In this paper, the Hojedk Formation in South Kouchekali, southwestern Tabas city, central east Iran was studied for palaeobotany and stratigraphy. This formation contains well preserved plant macrofossils belonging to 43 species assigned to 24 genera of various orders such as Equisetales, Filicales, Bennettitales, Cycadales, Caytoniales, Ginkgoales and Pinales. One biozone and four subzones are recognized. The lower and the upper boundaries of this assemblage biozone are identified by the first and the last observed occurrences of Coniopteris hymenophylloides (Brongniart) Seward, 1900 and Klukia exilis (Phillips) Raciborski, 1890, respectively. According to the occurrences of these index species and Ptilophyllum harrisianum Kilpper, 1968 and Nilssonia macrophylla Jacob & Shukla, 1955, an early Middle Jurassic (Aalenian-Bajocian) age is considered for this assemblage biozone. Moreover, a comparative biostratigraphy for the Middle Jurassic of Iran is suggested. As a result, the Coniopteris hymenophylloides- Klukia exilis Assemblage biozone is proposed as a biozone widespread through the whole Iranian Plate. On the basis of the relative abundance of Filicales, Pinales, Cycadales, and Equisetales and of the high diversity and abundance of macrophyllous cycadophytes (eight species), a humid sub-tropical climate is suggested for this locality. In addition, floral gradient, correspondence analysis and similarity index were considered. Therefore, it is confirmed that a uniform palaeoclimate and vegetation cover occurred in Iran during the Middle Jurassic and that Iran was located within Vakhrameev's Euro-Sinian Region. [ABSTRACT FROM AUTHOR]

Abstract: Exposure to recurrent desiccation cycles carries a risk of accumulation of reactive oxygen species that can impair leaf physiological activity upon rehydration, but changes in filmy fern stress status through desiccation and rewatering cycles have been poorly studied. We studied foliage photosynthetic rate and volatile marker compounds characterizing cell wall modifications (methanol) and stress development (lipoxygenase [LOX] pathway volatiles and methanol) through desiccation–rewatering cycles in lower‐canopy species Hymenoglossum cruentum and Hymenophyllum caudiculatum, lower‐ to upper‐canopy species Hymenophyllum plicatum and upper‐canopy species Hymenophyllum dentatum sampled from a common environment and hypothesized that lower canopy species respond more strongly to desiccation and rewatering. In all species, rates of photosynthesis and LOX volatile emission decreased with progression of desiccation, but LOX emission decreased with a slower rate than photosynthesis. Rewatering first led to an emission burst of LOX volatiles followed by methanol, indicating that the oxidative burst was elicited in the symplast and further propagated to cell walls. Changes in LOX emissions were more pronounced in the upper‐canopy species that had a greater photosynthetic activity and likely a greater rate of production of photooxidants. We conclude that rewatering induces the most severe stress in filmy ferns, especially in the upper canopy species. [ABSTRACT FROM AUTHOR]

Hymenoglossum cruentum (Cav.) Presl. and Hymenophyllum dentatum (Cav.) are poikilohydric partial desiccation tolerant (PDT) epiphytic filmy ferns with contrasting vertical distributions. H. cruentum is restricted to trunk base (ground to 1 m), and H. dentatum is more generalist growing from the ground up to 9 m in the host. Vertical distribution has been related to interspecific differences to cope with greater desiccating conditions such as low humidity and high irradiance. PDT plants exhibit a series of mechanisms that allow them to better tolerate severe dehydration that include the accumulation of compatible solutes, and the de novo synthesis of proteins and free sugars that are thought to protect cellular structure during cycles of desiccation-rehydration. Therefore, interspecific differences in the capacity to accumulate compatible solutes and metabolites during desiccation-rehydration may explain differences in vertical distribution between these two “filmy fern” species. The contents of proline, glycine betaine, soluble sugars, total proteins, and pigments of the photosynthetic system were evaluated during a cycle of desiccation-rehydration in H. cruentum and H. dentatum. The latter exhibited a more rapid desiccation-rehydration cycle in contrast to the former. Soluble sugars, proline, and pigment contents decreased in the dehydrated state. The two filmy ferns did not exhibit a major accumulation of proline (lower than 8 μmol g −1  DW) or glycine betaine (lower than 4 mg g −1  DW) which contrasts with other higher plants exposed to water deficit. Both species exhibited an elevated sugar concentration in the hydrated state, which decreased during desiccation by approximately 2.5-fold. These results differ from previous studies on other desiccation tolerant higher-plants but agree with results from bryophytes. We concluded that accumulation of conventional compatible solutes of higher plants is not part of the dehydration induced mechanisms conferring desiccation tolerance in filmy ferns, and do not explain interspecific differences in vertical distribution of the two species. Therefore, partial desiccation tolerance of filmy ferns probably relies on preformed structural rather than induced biochemical mechanisms, suggesting similarities of Hymenophyllaceae (primitive ferns) with bryophytes. [ABSTRACT FROM AUTHOR]

Abstract: The filmy fern Hymenophyllum caudiculatum can lose 60% of its relative water content, remain dry for some time and recover 88% of photochemical efficiency after 30 min of rehydration. Little is known about the protective strategies and regulation of the cellular rehydration process in this filmy fern species. The aim of this study was to characterise the filmy fern ultrastructure during a desiccation–rehydration cycle, and measure the physiological effects of transcription/translation inhibitors and ABA during desiccation recovery. Confocal and transmission electron microscopy were used to compare changes in structure during fast or slow desiccation. Transcription (actinomycin D) and translation (cycloheximide) inhibitors and ABA were used to compare photochemical efficiency during desiccation recovery. Cell structure was conserved during slow desiccation and rehydration, constitutive properties of the cell wall, allowing invagination and folding of the membranes and an important change in chloroplast size. The use of a translational inhibitor impeded recovery of photochemical efficiency during the first 80 min of rehydration, but the transcriptional inhibitor had no effect. Exogenous ABA delayed photochemical inactivation, and endogenous ABA levels decreased during desiccation and rehydration. Frond curling and chloroplast movements are possible strategies to avoid photodamage. Constitutive membrane plasticity and rapid cellular repair can be adaptations evolved to tolerate a rapid recovery during rehydration. Further research is required to explore the importance of existing mRNAs during the first minutes of recovery, and ABA function during desiccation of H. caudiculatum. [ABSTRACT FROM AUTHOR]

The inventory of biodiversity in the Comoros archipelago is still in progress. We propose here to contribute to this effort by assessing the diversity of the Hymenophyllaceae family, which forms one of the most diverse and emblematic fern communities in rainforests of the region. Data were extracted from floras, literature, recent collects and observations, and from an exhaustive investigation of the Paris herbarium collection. We also completed an online knowledge database including a computer-aided identification (CAI) tool by using the Xper platform. Our checklist recognizes 21 taxa involving 1 endemic and 7 species newly reported for the archipelago. The taxonomy and discrimination of each taxon is discussed and a dichotomous key is provided. We also defined 80 morphological characters and their corresponding states into the Xper database and CAI that could be easily enriched for neighbouring areas and additional taxa.

We report on the occurrence of independent gametophytes of Didymoglossum petersii and both gametophytes and sporophytes of Vittaria graminifolia in the Broxton Rocks Preserve of southern Georgia. This is the first time sporophytes of V. graminifolia have been observed in the United States. In order to unambiguously identify both taxa, we extracted DNA for each. In the case of V. graminifolia, we used BLAST to compare our results to sequences in GenBank for two plastid loci ( rbcL and rpoA) to determine its affinities. Because there are no GenBank data for D. petersii, it was necessary to collect an additional specimen of this species for comparison in a phylogenetic analysis. Results confirm the identity of each specimen and provide insight into the biogeographic history of D. petersii. [ABSTRACT FROM AUTHOR]

Based on a worldwide dataset of molecular sequence data from three plastid DNA markers (rbcL, rbcL-accD-accD, rps4-trnS) obtained from 109 species of Hymenophyllum (Hymenophyllaceae), we investigated the systematics and biogeographic origins of the New Caledonian (NC) members of this fern genus, which were thought to include 16 species with 10 endemics. Located in the southwest Pacific, NC is a continental Gondwanan island that was long supposed to harbour phylogenetic relicts. However, molecular and geological data suggest that the current flora and fauna are the result of recent colonizations that occurred after total submersion (during the Eocene) and subsequent re-emersion of NC ca. 37 Ma. Our molecular phylogenetic results, complemented by morphological observations of herbarium specimens, show the existence of a new species that was as yet undescribed, and suggest that a previously recognized variety should be elevated to the rank of species to avoid species polyphyly. These two species, which are recognizable based on several morphological features, are endemic to NC: (i) Hymenophyllum soriemersum sp. nov. is sister to the other NC endemic H. dimidiatum; and (ii) H. neocaledonicum comb. & stat. nov, previously described as a variety within H. lyallii, was retrieved as a distinct lineage. We also confirmed the synonymy of H. streptophyllum and H. subdimidiatum (both previously considered as endemic to NC) with the more widely distributed H. javanicum and H. holochilum, respectively. These synonymies were previously hypothesised based on morphology alone. New Caledonia thus has as total of 17 Hymenophyllum species, 12 (71%) of which are endemics. Biogeographic inferences based on the results of our phylogenetic analyses suggest that Hymenophyllum originated in New Zealand ca. 49.8 Ma (95% HPD: 40.7--59.5 Ma). Its spatio-temporal history may in part have been influenced by vicariance (with potential exchange via the Antarctica land bridge that persisted between Australia and South America until 34 Ma), but long-distance dispersal (LDD) appears as the predominant process leading to the present-day distribution of species. At least eight LDD events are needed to explain the presence of the 10 NC endemics analysed here (H. francii and H. humboldtianum were not included), each of which occurred < 22.1 Ma and originated from a surrounding territory: Southeast Asia was probably the dispersal source for the NC endemic clade comprising H. soriemersum, H. dimidiatum, and H. rolandi-principis while the ancestors of the other NC endemics most likely dispersed from New Zealand, Australia or other Pacific Islands. Such a regional pattern is congruent with the distribution of non-endemic species, which are mostly shared among neighbouring territories. Lastly, we found evidence for only two cases of diversification within NC, yielding two and three species each (H. soriemersum, H. dimidiatum and H. rolandi-principis; and H. lyallii and the ancestor of H. braithwaitei and H. tomaniiviense). Such a low level of in situ diversification may be explained by the high dispersal abilities of ferns in general (via dust-like spores), which slow down the differentiation process among populations and make a newly available niche likely to be filled by an immigrant before a new species might evolve locally. [ABSTRACT FROM AUTHOR]

Hymenophyllaceae is the most rich speices family of leptosporangiate ferns. It mainly distributed in the humid tropics, possessing terrestrial, epiphytic, hemepiphytic and climbing ecotypes. To further understand the molecular adaptation linked to fern radiation, evolutionary patterns of the rbcL sequences in the family Hymenophyllaceae were examined using random-site models along with the estimated time-scale of Hymenophyllaceous phylogeny. By comparing Modles M1a/M2a and M7/M8 under random-site modles, six amino acid sites(125I, 227L, 231A, 258F, 304S and 351L)were found to be positively selected, in which the site 304S was located in the D-loop six, playing an important role in keeping Rubisco function. We also used CAPS v1.0(coevolution analysis using protein sequences)to study the evolutionary relationship between the amino sites within the Rubisco large subunit. Thirty-nine groups of coevolutionary sites were detected(totally thirty-five amino sites), of which 46% were located in the α-helix, 14% in the β-sheet. This complex evolutionary patterns may be related to its earlier origin. In view of this, the phylogenetic tree was reconstructed. The results showed that the initial divergence whin Hymenophyllaceae occurred in the early Triassic. The divergence within Trichomanes and Hymenophyllum occurred in the early Jurassic and Cretaceous, seperatelly. The results also indicated that the ancestral state for the Hymenophyllaceae was terrestrial, suggesting possible roles played by the Thermal Maximum recently. These results provide new insights for how Hymenophyllaceae ferns response to the terrestrial ecosystem changes caused by the rise angiosperms. [ABSTRACT FROM AUTHOR]

The improvement of the conservation and management strategies of endangered species requires an understanding of the history and current state of their populations and thus population genetic studies become essential. This situation is especially critical for the relict populations at the low-latitude limit of the species range, which have persisted at suitable sites across Tertiary and Quaternary climatic changes and are expected to have retained a high proportion of the genetic diversity of the species. Here we investigate the genetic diversity and structure of Vandenboschia speciosa, a vulnerable endemic European-Macaronesian species with a disjunct distribution, at its southernmost distribution limit in continental Europe (S Iberian Peninsula: Andalusia, Spain). We analysed six sporophyte populations from the eight known populations using ten microsatellite loci. The results indicated moderate genetic diversity at the regional scale but low diversity at the population level and a significant genetic differentiation between populations. Coalescent analyses revealed a population history in Andalusia characterized by a migration-drift equilibrium with historical dispersals as the main factors influencing population structure, but now predominately influenced by genetic drift, according to the genetic differentiation detected. Spatial autocorrelation and genetic-structure analyses (multivariate and STRUCTURE analyses) suggest that historic gene flow was mainly over short distances, since significant genetic relationships were detected between pairs of nearby populations (< 7 km). Only one population, the most diverse, shows evidence of long-distance dispersal. This study provides a baseline for designing appropriate conservation strategies for V. speciosa in Andalusia, where the regional government has recently approved a recovery and conservation plan. [ABSTRACT FROM AUTHOR]

The complete chloroplast genome sequence of Crepidomanes latealatum (Bosch) Copel. was determined in the present study. The genome is 145,943 base pairs (bp) in length and comprised two inverted repeats (32,990 bp) between a large single copy (92,170 bp) and a small single copy (20,783 bp). It contains 88 coding genes, 8 rRNA genes, 34 tRNA genes, and 1 pseudogene of trnL-UAA, and the GC content is 37.6%. Molecular phylogenetic analysis based on the plastid genome sequences of related taxa strongly supported the monophyly of the family Hymenophyllaceae, and the genus Vandenboschia was a sister group of Crepidomanes . In addition, compared to C. minutum, two large deletions of 453 bp and 878 bp were found in the IGS regions of petA-psbI and rrn16-trnV-GAC of C. latealatum cp genome, respectively., Competing Interests: The authors have no conflicts of interest in this study., (© 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)