Emily B. Sessa

Following decades of increasing collaboration and organization, the United States natural science collections community is uniting around the creation of a national center supporting biological collections. Community consultations identified eight major themes that a center could encompass to manage, unify, and strategically expand the vast specimen/sample infrastructure and associated data stored in biological collections, address challenges facing physical biodiversity collections, and, importantly, coordinate across diverse research and education sectors. The center would foster workforce development, ethical collaboration with Indigenous communities, expand a digital infrastructure to provide broad access to collections data, and innovation in fields like artificial intelligence for data capture, management, and analysis. Ultimately, a center would provide sustainable, long-term government and private support for biodiversity science that integrates the use of biological collections to foster innovations and networks that address critical societal challenges and benefit public health, environmental conservation, and the bioeconomy.

Functional and genomic studies on the differences between gametophyte and sporophyte life phases remain scarce, yet unraveling these dynamics is crucial to understanding the biology of plants and the success of each phase under different environments. Here, we provide a novel reference genome for the highly invasive fern Lygodium microphyllum and compare the transcriptomic and epigenomic landscapes of the gametophyte and sporophyte life phases. We found differential regulation of developmental genes (homeobox and MADS-box clades) and usage of alternative isoforms that may play a role in the genomic determination of the haploid and diploid life stages. We further generated the first base pair-resolution methylome of a fern gametophyte, and determined that methylation patterns are remarkably similar between vegetative tissues despite their morphological and functional differences. By examining the physiological and transcriptomic responses of gametophytes and sporophytes to freezing stress, the most likely abiotic factor preventing further expansion of this invasive species, we show that life phases and tissues use alternative molecular pathways to respond to this stressor, underscoring the need to incorporate both life phases when developing effective mitigation strategies. These new genomic resources fill a gap in our understanding of fundamental plant biology and inform invasive species research.

Summary: How asexually reproducing organisms maintain genetic diversity and adaptive potential is a long‐standing question in evolutionary biology. Asexual lineages have historically been thought of as evolutionary dead ends, yet some exhibit remarkable persistence through time. The gametophyte‐only fern Vittaria appalachiana is a clonal eukaryote, the focus of extensive study due to its peculiar habit and life history, and is an excellent system to explore the consequences of asexuality. Using reduced representation sequencing and life cycle simulations, we assess theoretical expectations for genomic consequences of long‐term asexual reproduction and test hypotheses about its origin and demographic history. We show that V. appalachiana colonies are not patches of single genotypes but are mosaics of genetic diversity, and the accumulation of mutations in the absence of recombination plays an important role in driving this diversity. We identify increased genomic variation, excess heterozygosity, decreased population differentiation, and increased effective population size, all of which are consistent with the expectations for prolonged clonality. Our analyses support the hypothesis that the loss of sexual reproduction in V. appalachiana occurred during the Last Glacial Maximum. Our results from empirical and simulation‐based analyses illuminate how an asexual eukaryote generates, retains, and partitions genomic diversity.

Societal Impact Statement: Biological samples and their associated information are an essential resource used by scientists, governments, policymakers, practitioners and communities to ensure that biodiversity can be appropriately protected and sustainably used. Yet, considering the enormous task of documenting the vast numbers of as‐yet‐unknown plant and fungal species, greater international coordination for biological collecting and recording is necessary, built on equitable collecting practices and standards. Here, we propose five commitments to accelerate and enhance scientific knowledge of plant and fungal diversity, while increasing collaboration, benefit sharing and efficiency.Summary: Almost all life depends on plants and fungi, making knowledge of their diversity and distribution—primarily derived from biological collections—fundamental to national and international conservation, restoration and sustainable use commitments. However, it is estimated that some 15% of all plant species and over 90% of all fungal species have not yet been scientifically described, hampering our ability to assess and demonstrate the impact of efforts to halt biodiversity loss. In addition, organisations and researchers around the world lack a concerted strategy for increasing complementarity and avoiding overlap in botanical and mycological research, particularly in relation to the collection of specimens. We here present the 2030 Declaration on Scientific Plant and Fungal Collecting, summarising a commitment towards such a necessary strategy. Its components were identified from discussions during and after a series of four workshops and plenary discussions at the 2023 State of the World's Plants and Fungi symposium convened by the Royal Botanic Gardens, Kew, and were then consolidated into the present form by the authors. The Declaration was subsequently opened up for endorsement by signatories. Collectively, we agree on a set of five commitments for cataloguing the world's flora and funga, designed to maximise efficiency, facilitate knowledge exchange and promote equitable collaborations: (1) use evidence‐based collection strategies; (2) strengthen local capacity; (3) collaborate across taxa and disciplines; (4) collect for the future; and (5) share the benefits. This Declaration is a first step towards increased global and regional coordination of scientific collecting efforts.

The use of herbaria for science and conservation is enabling greatly enhanced scopes and scales of discovery, exploration and protection of biodiversity. The availability of digital, open-access herbarium data is, perhaps counter-intuitively, expanding the use of physical collections by researchers who use digital collections to find specimens and then sample physical collections for multiomics investigations, including genomics, transcriptomics, metabolomics, proteomics and microbiomics. These investigations are leading to new scientific insights and supporting the development of conservation actions, but they come with a substantial cost: the partial or complete destruction of often irreplaceable specimens, which constitute a global heritage that should be permanently safeguarded for future reference. Here we provide a set of recommended best practices for the sustainable, equitable and ethical sampling of herbarium specimens. Our recommendations are intended for two complementary and partially overlapping audiences—users and stewards—who together build, use and protect herbarium collections.

Premise: The extraction of high‐quality RNA is the critical first step for the analysis of gene expression and gene space. This remains particularly challenging in plants, and especially in ferns, where the disruption of the cell wall and separation of organic compounds from nucleic acids is not trivial.Methods: We developed a cetyltrimethylammonium bromide (CTAB)‐based RNA extraction protocol that consistently performs well across a large phylogenetic breadth of ferns—a lineage of plants high in secondary compounds—and in an array of tissue types. Two alternative options (precipitation vs. clean‐up without intermediate precipitation) are presented, both of which yield high‐quality RNA extracts with optical density (OD) ratios of OD 260/280 = 1.9–2.1 and OD 260/230 > 1.6, and RNA integrity numbers >7.Conclusions: This study presents an efficient protocol for the extraction of high‐quality RNA from multiple tissues and across the fern phylogeny, a clade of plants that still lags behind other major lineages in the development of genomic resources. We hope that this method can be used to help facilitate the closing of this gap.

Premise: Reticulate evolution, often accompanied by polyploidy, is prevalent in plants, and particularly in the ferns. Resolving the resulting non‐bifurcating histories remains a major challenge for plant phylogenetics. Here, we present a phylogenomic investigation into the complex evolutionary history of the vining ferns, Lygodium (Lygodiaceae, Schizaeales).Methods: Using a targeted enrichment approach with the GoFlag 408 flagellate land plant probe set, we generated large nuclear and plastid sequence datasets for nearly all taxa in the genus and constructed the most comprehensive phylogeny of the family to date using concatenated maximum likelihood and coalescence approaches. We integrated this phylogeny with cytological and spore data to explore karyotype evolution and generate hypotheses about the origins of putative polyploids and hybrids.Results: Our data and analyses support the origins of several putative allopolyploids (e.g., L. cubense, L. heterodoxum) and hybrids (e.g., L. ×fayae) and also highlight the potential prevalence of autopolyploidy in this clade (e.g., L. articulatum, L. flexuosum, and L. longifolium).Conclusions: Our robust phylogenetic framework provides valuable insights into dynamic reticulate evolution in this clade and demonstrates the utility of target‐capture data for resolving these complex relationships.

Summary: Climate change is rapidly altering natural habitats and generating complex patterns of environmental stress. Ferns are major components of many forest understories and, given their independent gametophyte generation, may experience unique pressures in emerging temperature and drought regimes. Polyploidy is widespread in ferns and may provide a selective advantage in these rapidly changing environments. This work aimed to understand whether the gametophytes of allopolyploid ferns respond differently to climate‐related physiological stress than their diploid parents. The experimental approach involved a multifactorial design with 27 treatment combinations including exposure to multiple levels of drought and temperature over three treatment durations, with recovery measured at multiple timepoints. We measured Chl fluorescence from over 2000 gametophytes to evaluate stress avoidance and tolerance in diploid and polyploid species. Polyploids generally showed a greater ability to avoid and/or tolerate a range of stress conditions compared with their diploid counterparts, suggesting that polyploidy may confer enhanced flexibility and resilience under climate stress. Overall, these results suggest that polyploidy may provide some resilience to climate change in mixed ploidy populations. However, all species remain susceptible to the impacts of extreme drought and heat stress.

Natural history collections form the foundation of a comprehensive biodiversity infrastructure that supports research on the natural world. Like libraries, they provide extensive, documented, accessible reference material, a stable place for the permanent deposition of voucher material used in published research, and an archive of changing biodiversity. Natural history collections of plants—herbaria—have supported botanical scholarship for centuries.

Premise: Bryophytes form a major component of terrestrial plant biomass, structuring ecological communities in all biomes. Our understanding of the evolutionary history of hornworts, liverworts, and mosses has been significantly reshaped by inferences from molecular data, which have highlighted extensive homoplasy in various traits and repeated bursts of diversification. However, the timing of key events in the phylogeny, patterns, and processes of diversification across bryophytes remain unclear.Methods: Using the GoFlag probe set, we sequenced 405 exons representing 228 nuclear genes for 531 species from 52 of the 54 orders of bryophytes. We inferred the species phylogeny from gene tree analyses using concatenated and coalescence approaches, assessed gene conflict, and estimated the timing of divergences based on 29 fossil calibrations.Results: The phylogeny resolves many relationships across the bryophytes, enabling us to resurrect five liverwort orders and recognize three more and propose 10 new orders of mosses. Most orders originated in the Jurassic and diversified in the Cretaceous or later. The phylogenomic data also highlight topological conflict in parts of the tree, suggesting complex processes of diversification that cannot be adequately captured in a single gene‐tree topology.Conclusions: We sampled hundreds of loci across a broad phylogenetic spectrum spanning at least 450 Ma of evolution; these data resolved many of the critical nodes of the diversification of bryophytes. The data also highlight the need to explore the mechanisms underlying the phylogenetic ambiguity at specific nodes. The phylogenomic data provide an expandable framework toward reconstructing a comprehensive phylogeny of this important group of plants.