Germination of an invasive fern responds better than native ferns to water and light stress in a Mexican cloud forest

Comparative transcriptomics in ferns reveals key innovations and divergent evolution of the secondary cell walls

Ferns are essential for understanding plant evolution; however, their large and intricate genomes have kept their genetic landscape largely unexplored, with only a few genomes sequenced and limited transcriptomic data available. To bridge this gap, we generated extensive RNA-sequencing data across various organs from 22 representative fern species, resulting in high-quality transcriptome assemblies. These data enabled us to construct a time-calibrated phylogeny for ferns, encompassing all major clades, which revealed numerous instances of whole-genome duplication. We highlighted the distinctiveness of fern genetics, discovering that half of the identified gene families are unique to ferns. Our exploration of fern cell walls through biochemical and immunological analyses uncovered the presence of the lignin syringyl unit, along with evidence of its independent evolution in ferns. Additionally, the identification of an unusual sugar in fern cell walls suggests a divergent evolutionary trajectory in cell wall biochemistry, probably influenced by gene duplication and sub-functionalization. To facilitate further research, we have developed an online database that includes preloaded genomic and transcriptomic data for ferns and other land plants. We used this database to demonstrate the independent evolution of lignocellulosic gene modules in ferns. Our findings provide a comprehensive framework illustrating the unique evolutionary journey ferns have undertaken since diverging from the last common ancestor of euphyllophytes more than 360 million years ago.

Influence of habitat types and seasons on the composition and diversity of spontaneous species in the rural-urban fringe of Chengdu City, China

The rural-urban fringe (RUF) is the indistinct boundary zone outside the urban area. It is also a highly vulnerable, sensitive, and ecologically valuable space, owing to the complex demographic composition, unbalanced economic development, and dramatic changes in land use and ecosystems. Different plants spontaneously emerge across RUF areas, playing an important ecological role in regulating climate and providing varied habitats for plants and animals. Few studies on urban sprawl have examined the plant diversity of RUF areas. Thus, more information is needed about the composition, diversity, and variability of spontaneous RUF species. Accordingly, this research implemented a field study across 248 survey plots in the RUF of Chengdu City, China. The composition and diversity of spontaneous species in five RUF habitat types during different seasons were analyzed. The effects of habitat types and seasons on α-diversity and species composition dissimilarities were evaluated using two-way analysis of variance, Principal coordinates analysis, and pairwise permutational multivariate analysis of variance, respectively. Across the seasons, 313 species of spontaneous vascular plant were recorded in RUF plots. Escaped medical and edible species accounted for 53.04% of species, consistent with the RUF inhabitants' needs. Among exotic plants, 41 of 74 were invasive species posing a high risk of species invasion. Trees were the dominant vegetation type only in autumn; herbs were the dominant vegetation in other seasons. Both season and habitat types significantly affected spontaneous species composition and α-diversity; moreover, habitat type had a greater effect than season. Farmland, with the highest α- and β-diversity levels, had the optimal resilience under environmental change. Its species composition was most similar to that of building land. Furthermore, both farmland and road land exhibited a significantly elevated proportion of exotic species in comparison to other habitats. Exotic species easily spread to cities and villages through the connectivity of road lands and farmland. In contrast, woodland had the lowest adaptive capacity under environmental change, with the lowest α- and β-diversity levels. With the escalation of anthropogenic disturbance, the prominence of the dominant species within the community markedly increased. However, as the foundation of occasional species conservation, it is the most important habitat type to protect. This study contributes to the understanding of changes in ecological processes in the RUF of megacities caused by urbanization and provides an important reference for RUF habitat conservation.

A review of plants strategies to resist biotic and abiotic environmental stressors

Plants exposed to a variety of abiotic and biotic stressors including environmental pollution and global warming pose significant threats to biodiversity and ecosystem services. Despite substantial literature documenting how plants adapt to distinct stressors, there still is a lack of knowledge regarding responses to multiple stressors and how these affects growth and development. Exposure of plants to concurrent biotic and abiotic stressors such as cadmium and drought, leads to pronounced inhibition in above ground biomass, imbalance in oxidative homeostasis, nutrient assimilation and stunted root growth, elucidating the synergistic interactions of multiple stressors culminating in adverse physiological outcomes. Impact of elevated heavy metal and water deficit exposure extends beyond growth and development, influencing the biodiversity of the microenvironment including the rhizosphere nutrient profile and microbiome. These findings have significant implications for plant-stress interactions and ecosystem functioning that prompt immediate action in order to eliminate effect of pollution and address global environmental issues to promote sustainable tolerance for multiple stress combinations in plants. Here, we review plant tolerance against stress combinations, highlighting the need for interdisciplinary approaches and advanced technologies, such as omics and molecular tools, to achieve a comprehensive understanding of underlying stress tolerance mechanisms. To accelerate progress towards developing stress-tolerance in plants against multiple environmental stressors, future research in plant stress tolerance should adopt a collaborative approach, involving researchers from multiple disciplines with diverse expertise and resources.

Distribution and morphological variation of tree ferns (Cyatheaceae) along an elevation gradient

Knowing how species and communities respond to environmental change is fundamental in the context of climate change. The search for patterns of abundance and phenotypic variation along altitudinal gradients can provide evidence on adaptive limits. We evaluated the species abundance and the variation in morphometric and stomatal characters in five tree ferns species (Cyathea fulva, C. divergens, C. myosuroides, Alsophila firma and Gymnosphaera salvinii) distributed along an elevation gradient in a well-preserved Mexican cloud forest. Variation at the community and species level was assessed using exploratory and multivariate data analysis methods. We wanted to explore if the species abundance is environmentally determined, to determine the degree of variation along the elevation gradient, to test for differences between zones and associations with elevation, humidity and soil nutrients, and to assess contribution of the intra- and interspecific variation to the community response to elevation and soil nutrients. The studied fern community showed strong species turnover along the elevation gradient, with some influence of soil nutrient concentration, supporting environmental determinism. All measured characters displayed variation along the gradient. Stomatal characters (size and density) had significantly less variation than morphometric characters (trunk diameter, stipe length and blade length), but stomatal density also shows interesting intraspecific patterns. In general, patterns within the fern community suggest a strong influence of species identity, especially of species inhabiting the lower edge of the cloud forest, which showed the clearest morphometric and stomatal patterns, associated to contrasting environments rather than to changes in elevation. The coincidence between morphometric and stomatal patterns in this area suggest hydraulic adjustments in response to contrasting environments. Our results provide evidence that tree ferns species respond to environmental changes through adjustments of morphometric plasticity and stomatal density, which is relevant to predict possible responses to variation in environmental conditions resulting from climate change.

Dynamic genome evolution in a model fern

The large size and complexity of most fern genomes have hampered efforts to elucidate fundamental aspects of fern biology and land plant evolution through genome-enabled research. Here we present a chromosomal genome assembly and associated methylome, transcriptome and metabolome analyses for the model fern species Ceratopteris richardii. The assembly reveals a history of remarkably dynamic genome evolution including rapid changes in genome content and structure following the most recent whole-genome duplication approximately 60 million years ago. These changes include massive gene loss, rampant tandem duplications and multiple horizontal gene transfers from bacteria, contributing to the diversification of defence-related gene families. The insertion of transposable elements into introns has led to the large size of the Ceratopteris genome and to exceptionally long genes relative to other plants. Gene family analyses indicate that genes directing seed development were co-opted from those controlling the development of fern sporangia, providing insights into seed plant evolution. Our findings and annotated genome assembly extend the utility of Ceratopteris as a model for investigating and teaching plant biology.