Adiantum capillus-veneris is a species with a worldwide distribution, exhibiting considerable morphological variation, with several infraspecific names applied. Among these infraspecific taxa, A. capillus-veneris subspecies lanyuanum can be easily distinguished from typical A. capillus-veneris by its small and 1-pinnate fronds. This form has been recorded from a few insular populations in Taiwan and Japan, typically inhabiting moist and shaded coral reef cliffs. A chloroplast DNA phylogeny further demonstrates that collections of subsp. lanyuanum across different populations formed a well-supported clade, and also provides evidence of its genetic distinctiveness and differentiation. Further examination of herbarium specimens and field observations found that, in addition to frond morphology, the rhizome scale differences are also useful for distinguishing the two taxa. As a consequence, A. capillus-veneris subsp. lanyuanum comb. nov. is proposed as the appropriate taxonomic designation of this taxa and a neotype is designated.

Yakushima Island is a major biodiversity hotspot where complex environmental gradients and high endemism provide an ideal setting for studying plant evolution. In this study, we investigated the relationships among ploidy variation, morphology, and environmental factors in populations of Plagiogyria adnata, including the variety P. adnata var. yakushimensis. A total of 67 specimens were analyzed using flow cytometry and chromosome counts, complemented by spore measurements and morphometric analyses of both field-collected and herbarium material. Three cytotypes-tetraploid, pentaploid, and hexaploid-were identified, with tetraploids being the most widespread, while higher ploidy levels were restricted to specific localities. No significant relationship was found between ploidy level and elevation. However, hexaploid individuals produced significantly larger spores, enabling reliable discrimination from lower ploidy levels and facilitating ploidy inference in herbarium specimens. Morphological comparisons revealed limited differentiation among cytotypes, although hexaploids tended to have more numerous and narrower lateral pinnae. In contrast, most morphological traits showed strong correlations with elevation, with plants at higher altitudes exhibiting reduced size and increased leaf dissection, consistent with alpine dwarfism. This implies that morphological variations are more environmentally driven and that lineage distinction between varieties of P. adnata needs to be further assessed through genomic information. This study provides new insights into the distribution of polyploid lineages and demonstrates the utility of spore traits for cytotype identification, contributing to a better understanding of fern diversification and conservation in island ecosystems.

The filmy fern Abrodictyum asae-grayi (Hymenophyllaceae) is thought to be distributed from New Guinea to French Polynesia. However, specimens from the Marquesas Islands and some populations from the Society Islands show clearly erect rhizomes, while the species A. asae-grayi is described as having creeping rhizomes. In-depth examination of the herbarium specimens and phylogenetic analysis demonstrate that the specimens with creeping rhizomes and those with erect rhizomes define two distinct species. The new species, A. polynesicum, endemic to French Polynesia, is discussed and described here.

Advances in phylogenomics have greatly clarified fern evolutionary relationships, yet significant gaps remain. In this study, we performed phylogenetic and phylogenomic analyses of Polypodiineae, one of the most species-rich suborders of Polypodiales, and found that Tectaria tenerifrons is a deeply diverged lineage. Our results support it as sister to Nephrolepidaceae in the plastome dataset, whereas the transcriptome dataset recovered it as sister to a clade comprising Nephrolepidaceae, Polypodiaceae, Davalliaceae, Oleandraceae, Tectariaceae s.l. No results support it as a member of the Tectariaceae, where it was previously classified. To reflect this deep divergence, we establish a new family, Cryptocaulaceae fam. nov., and a new monotypic genus, Cryptocaulon gen. nov, and propose the new combination Cryptocaulon tenerifrons comb. nov. Morphologically, Cryptocaulon can be distinguished from Tectaria by a combination of characters: long-creeping carnose rhizomes; subclathrate scales with multicellular hairs; anastomosing venation forming multiple rows of areoles without free included veinlets; basal veinlets of pinna lobes on the basiscopic side arising from the pinnule costule; cristate perispores with short, thick ridges; basic chromosome number, x = 41. We also designated a lectotype for C. tenerifrons.

Abstract Taxonomy within Hymenophyllum subgenus Mecodium (Hymenophyllaceae) has long presented significant challenges due to high morphological similarity among species. In this study, we conduct a taxonomic revision by combining a literature review, morphological examination of herbarium specimens, field investigations, and phylogenetic analyses based on several chloroplast markers (rbcL, accD, rps4, rbcL-accD, and rps4-trnS). Our revision yields an updated checklist of Chinese Mecodium, comprising 11 species and one variety. Integrating four Hymenophyllum-associated fossils, we performed divergence time estimation using both CladeDate and tip-dating methods. We infer for the subgenus Mecodium an origin in the Palaeogene, and a single arrival in Continental Asia dated from the Eocene. Major diversification events in Asia appear to coincide with the Himalayan orogeny and Miocene climatic shifts. Biogeographical reconstruction indicates multiple dispersal routes, including transoceanic movement from East Asia to North America and southeastward expansion from the Himalayan region within Asia. These findings offer new insights into the evolutionary history of this taxonomically complex fern group.

Accumulating evidence suggests that speciation often resembles a reticulate network rather than a bifurcating process. In ferns, which possess independent gametophyte and sporophyte phases, reticulate evolution is common, especially where sporophytes of congeneric species co-occur. However, the role of long-lived gametophytes that distribute beyond their sporophytic counterparts in facilitating reticulate evolution remains underexplored. To address this gap, we investigated two species complexes of Haplopteris, a genus within one of the five lineages known to have evolved long-lived gametophytes. We integrated evidence from morphology, chromosome numbers, genome sizes, plastid DNA, and nuclear DNA, sampling comprehensively both gametophyte and sporophyte phases. We identified ploidy levels and genomic formulas of sampled individuals and reconstructed their reticulate evolutionary histories. Our results confirmed the reticulate evolution of Haplopteris for the first time and demonstrated that independent gametophyte populations, despite not producing their own sporophytes, play a critical role by contributing sperm to form hybrids. This study offers new insights into fern reproductive biology and gametophyte biogeography by reporting the first documented case of fern reticulate evolution involving both gametophyte and sporophyte samples, and the second known instance of hybridization involving independent gametophytes. Furthermore, a tetraploid species with a hybrid-origin is newly described.

Based on cytological analyses, phylogenetic analyses using chloroplast and nuclear genes, and morphological examination, Lepisorus tajimaensis T. Fujiw. (Polypodiaceae, Polypodiales) is described as a new allohexaploid species in the Japanese L. thunbergianus polyploid species complex. Our phylogenetic analyses demonstrated that L. tajimaensis originated through interspecific hybridization between L. nigripes and L. oligolepidus. The new species can be distinguished from L. nigripes by the broadly lanceolate rhizome scales (vs. narrowly lanceolate to lanceolate), lanceolate laminae (vs. linear to narrowly lanceolate), scales throughout the abaxial surface of the laminae (vs. scales mainly along costa on the proximal part of the abaxial surface of laminae), and larger sori (3-5 mm in diam.) (vs. 1-2.5 mm in diam.), and from L. oligolepidus by the brown rhizome scales with 3 or 4 rows of marginal transparent lumina (vs. dark brown rhizome scales with 1 or 2 rows of transparent marginal lumina), the light brown leaf scales (vs. dark brown), and sori being closer to the margin (vs. sori nearer costa). Additionally, sterile pentaploid hybrids resulting from backcrossing between L. tajimaensis and one of the parental species, L. nigripes is reported.

South and Southeast Asia are considered important centers of diversity for scaly tree ferns (Cyatheaceae). Following an extensive review of existing checklists from each Asian country, combined with the expert knowledge of the authors, a comprehensive checklist was compiled. The checklist comprises 185 species belonging to four genera: Alsophila (92 spp.), Cyathea (1 sp.), Gymnosphaera (27 spp.), and Sphaeropteris (65 spp.). Indonesia harbors the highest number of species (117), followed by Malaysia (including Malaysian Borneo) and the Philippines, each with 39 species, highlighting Indonesia's exceptional contribution to the region's species diversity. Indonesia also exhibits the highest level of endemism, with 48 endemic species (26%), while the Philippines and Malaysia have 25 and 12 endemic species, respectively. When considering the proportion of endemic species relative to the total number of species recorded in each country, Sri Lanka ranks first, with 71% endemism. The genus Alsophila significantly contributes to endemism in India, Indonesia, Malaysia, the Philippines, and Sri Lanka. The genus Alsophila accounts for 100% of the endemic species in Sri Lanka, while the genus Gymnosphaera accounts for 100% of the endemic species in Vietnam. We hope that this checklist will provide a useful foundation for future studies in taxonomy, biogeography, and conservation, and will contribute to informed management and protection of these species in their natural environments.

This study revises the taxonomy of Cephalomanes javanicum (Hymenophyllaceae), a filmy fern traditionally considered widespread across the Indomalayan and Australasian regions. Through a comprehensive analysis of the literature, type specimens, and herbarium collections, we clarify the taxonomic status of three recognized varieties: typical C. javanicum, C. javanicum var. sumatranum, and C. javanicum var. asplenioides. Morphological, morphometric, and molecular phylogenetic investigations reveal that these varieties represent distinct species rather than intraspecific variants. Additionally, we reassess C. atrovirens, a species often confused with C. javanicum, and confirm that its two previously recognized subspecies also warrant species status. Based on these findings, we propose the elevation of the C. javanicum varieties and C. atrovirens subspecies to full species rank, providing updated taxonomic treatments, synonymy lists, and new lectotypifications. These revisions contribute to a more accurate understanding of species diversity within Cephalomanes and have broader implications for fern taxonomy, biogeography, and conservation in the tropical Asia, Australasian, and Oceanian regions.

Many plant species experience a prolonged subterranean phase during which they rely entirely on mycorrhizal fungi for carbon. While this mycoheterotrophic strategy spans liverworts, lycophytes, and ferns, most empirical research has centered on angiosperms. This study explores the fungal associations of Sceptridium (Ophioglossaceae), an early-diverging fern with mycoheterotrophic gametophytes. We analyzed germination patterns and fungal associations in Sceptridium gametophytes, comparing them to the distribution and mycorrhizal partners of photosynthetic sporophytes. High-throughput sequencing data reveal that mycoheterotrophic gametophytes consistently associate with a single Entrophospora fungus in the order Entrophosporales (Glomeromycotina), while photosynthetic sporophytes primarily partner with fungi from Glomeraceae (Glomerales, Glomeromycotina). Consequently, gametophytes exhibit spatial clustering without association with adult plants. This is the first documentation of an association between Entrophosporaceae (and the order Entrophosporales) and mycoheterotrophic plants. The drastic shifts in Sceptridium mycorrhizal communities across life stages likely reflect changing physiological needs during development. Further research is essential to determine whether the association with Entrophosporaceae is widespread among mycoheterotrophic species and to elucidate the functional and physiological mechanisms underlying these mycorrhizal shifts.

Summary We describe and illustrate the evergreen and epiphytic fern Lepisorus boninensis (H.Christ) Ching, endemic to the Bonin Islands in Japan. This species can be recognised by the dimorphic leaves, the ovate and clathrate scales on the rhizome, and the irregularly‐shaped paraphyses growing between sporangia of the sori.

Transferring biochar nanomaterials (BNMs) from laboratory studies to field applications has significant implications for environmental remediation and sustainable agriculture. This comprehensive review synthesizes current knowledge on BNM fabrication, modification, applications, and research gaps to provide a foundation and future research agenda for their sustainable translation from lab to field. BNMs exhibit unique properties, such as high surface area of 50 -500 m 2 /g, porosity of 0.2 -0.7 cm 3 /g, and abundant oxygen-containing surface groups, enabling effective pollutant adsorption. Various feedstocks, including agricultural waste, sewage sludge, and manure, and thermochemical processes can be used to produce BNMs, while modification techniques, such as acid/alkali treatment, metal oxide incorporation, and biological modification, can further enhance their properties and pollutant removal efficiency. BNMs have demonstrated impressive contaminant removal capabilities in laboratory studies, often exceeding those of unmodified biochars by several fold. In agricultural applications, BNMs have shown potential to improve plant growth, soil fertility, and disease resistance. However, critical knowledge gaps exist regarding the real -world efficacy, safety, and sustainability of BNMs. Priority research directions include optimizing production and modification processes, investigating adsorption kinetics and binding mechanisms, conducting pilot-scale trials, and evaluating potential negative impacts. To facilitate the responsible translation of BNMs from laboratory to field, interdisciplinary collaboration, standardized testing protocols, and comprehensive ecological risk assessments are needed. By addressing these research gaps and prioritizing environmental and health safeguards, the sustainable deployment of BNMs can be achieved, offering a promising solution for restoring degraded environments and supporting sustainable food production.

Previous works indicate that the fern genus Abrodictyum (Hymenophyllaceae) comprises between 17 and 26 species in Asia, Australasia and Oceania. To clarify the diversity of the genus within this broad region, a taxonomic review was carried out via an in-depth examination of literature data, online databases and herbarium material. The result is an updated list of 18 distinct species, 2 varieties and 1 forma, including a corrected list of synonyms and the updated distribution of the taxa. The potential synonymisation between two species (A. clathratum and A. idoneum) is discussed and an identification key is proposed.

Callistopteris superba is a peculiar Asian species within the genus Callistopteris (Hymenophyllaceae). A detailed morphological study of available herbarium specimens was conducted and the species was integrated into a global molecular phylogeny of the family in order to more precisely investigate its taxonomy. Morphological analysis and dated phylogenetic reconstructions demonstrate that the species is not part of Callistopteris and is instead strongly supported as being included in the distinct genus Trichomanes, comprising mainly Neotropical and some Afro-Malagasy species. The uniqueness, within the Hymenophyllaceae and the genus Trichomanes, of an indumentum of glandular-like hairs on the adaxial side of the lamina and on the indusia, allows us to propose Asiatrichomanes as a new subgenus based on this species, which is here also neotypified.

HERBARIUM PLANT SPECIMENS AND THEIR HERBARIUM HOLDINGS Natural history collections around the globe represent a dormant source of taxonomic and biogeographic information, as it is estimated that one to three billion specimens are included in such collections (Soberon 1999; Ariño 2010). In the case of botanical collections, the worldwide distribution of specimens across herbaria is often uneven and biased by colonialism, with most specimens housed in the global North, and in many cases resulting in a reverse latitudinal relationship between plant diversity present in nature and the location of the herbaria housing it (Park et al. 2023). As an example, Yong (2013) reviewed holdings of common and type specimens and concluded that the type specimens’ accumulation in China is less than the world average. The number of type specimens is an important reflection of botanical accumulation in a country, and the number of specimens and their origins are therefore very important in a globalized framework. Accordingly, efforts to catalogue and digitize collections, and to make them globally accessible, are important tasks for herbaria. HERBARIA IN JAPAN AND THE UNIVERSITY OF TOKYO (TI) HERBARIUM In Japan, 74 herbaria are registered in Index Herbariorum (Thiers 2024), accounting for more than 13 million plant specimens. Herbaria in Japan date from the 19th century, with the first herbarium founded in Japan being the University of Tokyo’s (TI) herbarium (Herbarium of the University of Tokyo 2021) established in 1877. The herbarium holds a collection of more than 1,800,000 specimens of vascular plants, corresponding to ca. 14% of the total botanical collection of Japan. Although there is no complete survey of the number of specimens in the collection, it is estimated that the TI herbarium holds 20,000 type specimens, corresponding to 1% of the total number in the collection. Within the type specimens, only a fraction of the collection is digitized and available online, including 3,793 type specimens of angiosperms (and 1,743+ type specimens from other groups newly photographed in the last year). Regarding the ferns and lycophytes, the TI herbarium holds 35 families, including more than 300,000 specimens, comprising 1068+ type specimens (with 321 confirmed holotypes, 127 isotypes, and 510 syntypes), which are now being databased. The TI herbarium fern and lycophyte type collection includes plants from Japan, and important collections from Korea, Manchuria, Taiwan, and many Southeast Asian countries. Collections from outside Japan were mainly gathered by Japanese botanists that were assigned to expeditions in those countries, as Japan’s national power increased rapidly after the Meiji restoration (1869–1889). For example, Takiya Kawakami, originally from the Hokkaido University, actively worked on collecting plants from Taiwan; Hiroshi Hara worked on the Himalayan flora; Takenoshin Nakai worked on the Korean flora and collected medicinal plants from Indonesia and Ceylon (Sri Lanka); and Bunzo Hayata made a huge contribution to Taiwan’s flora. The specimens collected hold not only information on the taxonomic diversity, but also reflect historic events between Japan and these adjacent countries, thus proper curation of these materials is of great importance. The TI herbarium also holds unique collections, including many fern specimens collected from Seram Island (Indonesia), South America’s Andes collections by Fumio Maekawa, and Brazil’s Amazon collections by Masayuki Takeuchi. THE HIDDEN POTENTIAL OF THE TI HERBARIUM AND FUTURE PROSPECTS The TI herbarium collection is an important resource of natural history information, but its potential is still hindered by its incomplete databasing. In the Global Biodiversity Information Facility (GBIF) database, the Tracheophyta data from Japan currently consists of 3,503,623 herbarium specimens (GBIF.org 2024). Most of the data is from the TNS herbarium (500,060 specimens, National Museum of Nature and Science 2024), Kanagawa Prefectural Museum of Natural History (318,574 specimens, Kanagawa Prefectural Museum of Natural History 2024) and Nagano Environmental Conservation Research Institute (170,889 specimens, Nagano Prefecture 2023). The University of Tokyo's TI herbarium data only contains 40,382 specimens, not including any ferns or lycophytes, restricting access to the collection for researchers abroad. The TI herbarium mission now is to properly catalogue and make that information available, especially to those based in regions from where the plants were originally collected. Since 1981, many scientists have contributed to the cataloguing of the type specimens in the TI herbarium, with some of this data made available online. However, it is estimated that this database covers less than 10% of the collection, and does yet not include the ferns or lycophytes. We see the development of an open-access database for the TI herbarium as of utmost importance, as the herbarium represents an important historical and biodiversity account for East Asia.

The fern independent gametophytes that can maintain populations by vegetative reproduction without conspecific sporophytes have been considered an unusual phenomenon found in some epiphytic or epilithic species of Hymenophyllaceae, Pteridaceae, Lomariopsidaceae, and Polypodiaceae. By chance, the discovery of mysterious strap-like gametophytes on Izu-Oshima Island, Japan, has led to the hypothesis that Hymenasplenium murakami-hatanakae, a fern species belonging to Aspleniaceae, can also form independent gametophytes. Our investigation revealed gametophyte populations of H. murakami-hatanakae on three islands in the Izu Islands. Based on chloroplast DNA analysis of the gametophyte and sporophyte populations, the gametophytes were found to be maintained by vegetative reproduction without a new supply of spores from sporophytes. A comparison of the surrounding vegetation at the collection sites showed that environmental factors such as light and humidity may influence the maintenance of gametophyte populations. These results clearly show that H. murakami-hatanakae is one of the ferns capable of forming independent gametophytes. This is the first report of independent gametophytes from the suborder Aspleniineae (eupolypod II). The discovery of the independent gametophyte within a phylogenetic lineage previously thought not to form independent gametophytes will provide important insights into the morphological and functional evolution of gametophytes in ferns.

ForAspleniumsarelii Hook. (Dol-dam-go-sa-ri in Korean), recognized inKorea, it has been proposed thatsome populations of the species should be verified as A.anogrammoides Christ (2n = 4x = 144 based on its chromosome number counted from Jap-anese populations). Asplenium anogrammoides has been hypothesized as a polyploid spe-cies derived from a hybrid between A.sarelii (2n = 2x = 72)and A.tenuicaule Hayata (2n =2x = 72) based on its chromosome number counted from Japanese populations. To clarify theidentity of A. anogrammoides in Korea, the morphological, cytological, and molecular char-acters were examined. Morphologically variable individuals of A.anogrammoides werefound in sympatric regions with A. tenuicaule and A. pekinense. We investigated ploidy lev-els using flow cytometry data as well as the chloroplast DNA sequence data of two regions(rbcL; rps4-trnS and rps4-trnS intergenic spacer) to clarify the taxonomic status of this spe-cies. The chloroplast DNA (rbcL and rps4-trnS) indicated monophyly of the A. anogram-moides complex, although there were a few polyphyletic phenomena within the populations.With regard to the genome size data (flow cytometry) and chromosomes numbers, the A.anogrammoides complex from Korea contains mostly hexapodids, rarely tetraploids, and wecannot find diploid individuals. Based on these results, we hypothesize that the A. anogram-moides complex in Korea is mostly fertile hexaploids that arose due to autotetraploidy fromA. x huawuense (3x), which formed between A. sarelii and A. anogrammoides. In addition, itis postulated that there are sp1 (6x), sp2 (6x), and sp3 (6x) due to the sharing of morpho-logical characters among A. sarelii,A. tenuicaule, A. anogrammoides, and A. pekinense.

A new hybrid, Dryopteris xmakabensis (Dryopteridaceae) is described from Ibaraki Prefecture, Japan. Morphological observations, ploidy analysis, as well as nuclear and plastid DNA analyses, indicate that this diploid sterile hybrid likely originated from a cross between D. caudipinna and D. tokyoensis. Its occurrence is likely infrequent because the habitats of the parents are usually non -overlapping in Japan.

Previous phylogenies showed conflicting relationships among the subfamilies and genera within the fern family Ophioglossaceae. However, their classification remains unsettled where contrasting classifications recognize four to 15 genera. Since these treatments are mostly based on phylogenetic evidence using limited, plastid-only loci, a phylogenomic understanding is actually necessary to provide conclusive insight into the systematics of the genera. In this study, we have therefore compiled datasets with the broadest sampling of Ophioglossaceae genera to date, including all fifteen currently recognized genera, especially for the first time the South African endemic genus Rhizoglossum. Notably, our comprehensive phylogenomic matrix is based on both plastome and mitogenome genes. Inferred from the coding sequences of 83 plastid and 37 mitochondrial genes, a strongly supported topology for these subfamilies is presented, and is established by analyses using different partitioning approaches and substitution models. At the generic level, most relationships are well resolved except for few within the subfamily Ophioglossoideae. With this new phylogenomic scheme, key morphological and genomic changes were further identified along this backbone. In addition, we confirmed numerous horizontally transferred (HGT) genes in the genera Botrypus, Helminthostachys, Mankyua, Sahashia, and Sceptridium. These HGT genes are most likely located in mitogenomes and are predominately donated from angiosperm Santalales or non-Ophioglossaceae ferns. By our in-depth searches of the organellar genomes, we also provided phylogenetic overviews for the plastid and mitochondrial MORFFO genes found in these Ophioglossaceae ferns.