1. Traditionally managed grasslands are among the most biodiverse habitats in Europe, but are threatened by land use abandonment. While the negative impacts of grazing and mowing cessation on species richness are well documented, little is known about potential evolutionary changes within species. Yet, intraspecific functional diversity is critical for successful grassland restoration and ensuring adaptive potential to future climate change. 2. To disentangle the heritable and non-heritable components of population-level response to land use change in semi-natural grasslands, we examined 22 populations of a common grass, Briza media, from grazed sites and sites where grazing was abandoned, with resulting tree and shrub encroachment. We measured a range of traits under field conditions and following clonal propagation under common garden conditions. 3. Field surveys revealed that abandonment resulted in litter accumulation, greater shading by woody and herbaceous vegetation, and lower temperature and moisture fluctuations compared with grazed sites. Plants responded to conditions at abandoned sites with phenotypic plasticity in traits that enhanced competitive ability for light (greater height and specific leaf area) but reduced tissue protection against stress (lower dry matter content). However, when the same genotypes were measured after clonal propagation in common conditions, counter-gradient variation was apparent, with heritable shifts towards increased tissue protection in populations from abandoned sites. 4. When measured under field conditions, trait diversity was higher in sites with higher levels of shading and productive sites with higher variation in light conditions. However, high heritable trait diversity was instead characteristic of grazed sites with high densities of flowering B. media individuals. 5. Synthesis. These findings demonstrate that land use change can cause evolutionary shifts and changes in heritable trait diversity that are masked in the field by phenotypic plasticity. Hence, the assessment of functional trait variation based on field observations is not a reliable way to assess the genetic variation essential for population adaptive potential.

Woody vegetation encroachment in unmanaged semi-natural grasslands leads to a decline in plant diversity and alters community composition. Livestock grazing reinstatement can reverse this succession. However, despite their importance for terrestrial biodiversity and ecosystem processes, the dynamics of associated soil microbial communities are not well understood. We examined plant and soil microbial communities, including fungal (arbuscular mycorrhizal, ectomycorrhizal, pathogenic, saprotrophic) and prokaryotic (rhizobia, non-rhizobial bacteria, archaea) communities, in mountain grasslands in the central Pyrenees experiencing different degrees of management and overgrowth by woody vegetation. We found that plant richness declines and plant community composition changes substantially during woody encroachment. Analogous trends were observed in soil microbial communities, with AM fungal and bacterial communities showing the most distinct successional trajectories. A notable contrast was the significant increase in the richness of ECM fungi under the developing pine canopy. Livestock grazing reinstatement influenced soil microbial community composition but did not significantly affect plant community composition. Plant and soil microbial communities change synchronously during woody plant encroachment following livestock grazing cessation. Changes in plant communities are most pronounced, but strongly correlated changes also occur among AM fungi, pathogenic fungi and rhizobia, which have strong functional links with plants as symbionts or antagonists. Responses to restored livestock grazing were more apparent in soil microbial communities than plant communities, probably reflecting differences in diaspore persistence or dispersal efficiency.

Species-specific feedback between plants and soil microbial communities is an important driver of vegetation dynamics. Arbuscular mycorrhizal (AM) fungi colonise most terrestrial plants but are not expected to generate specific feedbacks due to low host specificity. We tested whether variation in mycorrhizal associations and associated rhizosphere metabolomes among co-existing temperate grassland species leads to species-specific plant-soil feedback. More mycorrhizal plant species showed more divergent plant-soil feedback: they experienced reduced growth and mycorrhizal colonisation in soils originating from weakly mycorrhizal species, but feedback became neutral in soil from species with similar mycorrhizal strategies. The species with the most self-promoting soil feedback was characterised by strong metabolome shifts related to stress and immune responses following soil inoculum manipulation, while the metabolomes of species with more negative feedback were unresponsive. This study demonstrates that AM fungi can generate species-specific plant-soil feedback, which can be predicted from plant mycorrhizal strategies and rhizosphere chemistry.

Ecosystems worldwide face growing impacts from non-native species invasions. However, little is known about how soil microbial communities respond to the addition of non-native plants, and whether these responses differ along a successional gradient. To address these knowledge gaps, we collected soil samples, recorded plant species cover and measured the traits of the plant species in lava flow vegetation and lowland rainforest (representing early and late successional stages) on La Réunion Island. Our results show that non-native plant cover drives variation in plant species diversity, community composition, functional composition (community-weighted means of vegetative height and leaf area) and functional diversity (mean pairwise trait distance among species), with these effects being stronger in early than in late successional stage. Non-native plant cover did not affect the diversity or community composition of soil fungi and bacteria. Instead, the functional diversity of plant communities associated with non-native plant addition explained the variation in soil microbial community composition and co-occurrence network structure. These results suggest that while non-native plant cover is a good indicator of variation in plant community composition, the functional diversity of the plant community is more useful for describing shifts in soil microbial communities of invaded habitats along primary succession.

Increasing frequency and intensity of droughts threaten grassland ecosystems. Semi-natural grasslands vary in age from ancient to younger sites established on former arable land. While species richness and composition are known to affect drought resilience, little is known about how grassland age shapes drought responses through eco-evolutionary processes at the plant population level. We explored how grassland age and local plant-soil adaptation shape the drought resilience of plant populations by reciprocally combining soils and genotypes of a common grass, Briza media, collected from young, intermediate, and ancient grasslands - last cultivated 28-63, 63-84, and > 84-300 years ago, respectively-and subjecting the resulting mesocosms to a drought event. Ancient grassland soils enhanced drought resistance and recovery compared with younger soils. Enhanced drought resilience was primarily explained by lower abundance of putative fungal pathogens in older soils. Plants grown in 'home' soils from their sites of origin were more productive and invested less in root production to withstand water stress, indicating the important role of local plant-soil adaptation. Our results show the long-lasting legacy of land use history in soil microbial communities and their significant role in shaping drought resilience across grassland populations.

Plants are consumed by a variety of organisms, including herbivores and pathogens, which significantly impact plant biomass, diversity, community composition, and ecosystem functioning. While the impacts of vertebrate herbivores are well established, the effects of consumer groups such as insect herbivores, mollusks, and fungal pathogens on plant communities are less clear and remain understudied in many systems. Existing evidence of how they affect plant biomass, diversity, and community composition is mixed, and most studies have focused on individual consumer groups in isolation. However, different consumer groups interact with each other, directly or indirectly, in ways that alter their impacts on plants, and the consequences of these interactions for plant community structure and ecosystem function remain understudied. Further, consumer impacts vary across environmental gradients and likely depend on abiotic conditions such as climate, soil type, or elevation, and biotic conditions such as plant productivity, diversity, or community composition. Existing studies testing the impacts of invertebrate herbivores and fungal pathogens on plant communities differ substantially in methodology, making generalities across large scales difficult. This calls for experimental approaches that implement standardized protocols across many sites. Here, we introduce and report on the methodology of a novel global research network, The Bug-Network (BugNet), that implements standardized consumer-reduction experiments across 5 continents and 18 countries in diverse, herbaceous- or shrub-dominated ecosystems to investigate: (1) the influence of fungal pathogens, insect herbivores, and mollusks on plant diversity and ecosystem functioning, (2) interactions among these consumer groups, and (3) the abiotic and biotic drivers of context-dependent consumer impacts. BugNet aims to advance a predictive understanding of plant-consumer interactions in order to test fundamental ecological hypotheses and improve predictions of global change impacts on biodiversity and ecosystem functioning.

MotivationArbuscular mycorrhizal (AM) fungi are central to plant nutrient acquisition, soil carbon dynamics, and ecosystem resilience. Yet, their biogeography remains incompletely characterised, particularly across underrepresented regions. Australia, with its characteristic ecological conditions, continental scale, and long-standing evolutionary trajectories, has been notably undersampled. This gap hinders our ability to make comprehensive inferences about AM fungal diversity, community composition, and ecological roles at global scales. The AusAMF database was created to address this deficiency by compiling high-throughput AM fungal community data across mainland Australia and Tasmania. The initial release comprises data from 610 georeferenced sites sampled between 2011 and 2023, covering all major climate zones and accompanied by standardised soil storage, DNA extraction, and sequencing procedures. Developed through a nationally coordinated effort, AusAMF offers a rare level of methodological consistency, enabling robust spatial and temporal comparisons while minimising post-sampling technical biases. Its design as a purpose-built, extensible platform ensures continued expansion using harmonised protocols-something not achieved through compiled datasets assembled retrospectively from disparate studies. Each sample is linked to associated environmental variables, allowing users to explore ecological drivers of AM fungal distributions, assess patterns of biodiversity, and support applications spanning from fundamental ecology to conservation planning. As such, AusAMF advances both regional and global efforts to characterise the diversity and ecological significance of these foundational plant symbionts.Main Types of Variables ContainedGeoreferenced occurrence and abundance of high-throughput amplicon sequences of arbuscular mycorrhizal fungi.Spatial Location and GrainAustralia. Decimal degrees between 0.0001 and 0.1 resolution.Time Period and Grain2011-2023. Month and year of sampling.Major Taxa and Level of MeasurementArbuscular mycorrhizal fungi identified to family, genus, and virtual taxon (VT). Geographic occurrence and amplicon sequence abundance.Software FormatInteract with processed data via online application (). Dataset available as .csv files and raw sequencing data as .fastq files.

Soil microbes are essential to maintain terrestrial ecosystem functionality. However, their diversity is threatened by land-use change, such as agricultural expansion and intensification. One important microbial group mediating the exchange of nutrients between plants and soil is arbuscular mycorrhizal (AM) fungi. The response of microorganism diversity to present and past habitat amount has been poorly studied. Here, we evaluate the potential role of current and historical natural habitat availability in explaining the diversity of AM fungi in arable fields. We conducted a spatially intensive sampling of three agricultural fields in Estonia. Soil AM fungal diversity was determined by soil DNA metabarcoding. We related AM fungal species richness, along with beta diversity components (turnover and nestedness), to abiotic conditions and natural habitat area availability at different spatial scales and time periods. Our findings showed a positive relationship between AM fungal richness and the amount of natural habitat area. Specifically, current AM fungal species richness was best explained by the amount of natural habitat from 130 years earlier, indicating a legacy effect of past land use on current soil biodiversity. The amount of past natural areas was negatively related to the beta diversity turnover component, indicating a replacement of AM fungal species in disturbed sites. While biodiversity-friendly farming is useful in promoting diverse soil biota, historical legacies can be persistent. Maintaining natural habitats around agricultural fields can further promote soil AM fungal diversity for future generations.

1. Land use change can cause the loss of plant species and functional diversity, but whether it drives eco-evolutionary changes within plant species is unclear. 2. Semi-natural grasslands are particularly threatened by land use change, including management intensification on productive soils and abandonment on marginal land. As such, they serve as an excellent system for exploring if and how land use change causes evolutionary changes within plant populations and what their wider consequences could be. 3. Here we synthesise what is known about land use impacts at the plant community and ecosystem level, build predictions on potential evolutionary responses and review empirical evidence available to date. We predict that land use intensification and abandonment may cause genetic and functional shifts in grassland plant populations, disrupt plant-microbial associations and create eco-evolutionary feedbacks that impact wider ecosystem processes. Evolutionary responses to land use may also undermine the adaptive potential of plant species to future climate change. 4. Synthesis: This review highlights the lack of studies on eco-evolutionary dynamics in ecosystems under land use change, despite their potential importance for the functioning and stability of plant and soil communities and the ecosystem processes that they maintain.

Mycorrhizal symbiosis, specifically arbuscular mycorrhiza, is one of Earth's oldest and most widespread symbiosis. Existing evidence suggests that plant species differ in their associations with mycorrhizal partners, with different species reported to be always (obligately mycorrhizal, OM), sometimes (facultatively mycorrhizal, FM) or never (non-mycorrhizal, NM) associating with arbuscular mycorrhizal (AM) fungi and this plant reliance on AM fungi is called plant mycorrhizal status. However, very little is known about how host plant mycorrhizal status shapes the network topology of interacting AM fungi. Here, we use a standardized sampling scheme to test whether plant species with different mycorrhizal statuses differ in mean AM fungal hyphal colonization and various indices of the AM fungal networks such as nestedness rank and resource range. We collected the roots and rhizosphere soil of 19 plant species representing five families. Each plant species was sampled from three distinct habitats. We determined AM fungal colonization in the roots and AM fungal community composition in roots and rhizosphere soil using molecular methods. We found that previously reported NM plant species had lower mean AM fungal colonization than FM plant species, but no differences were found between FM and OM plant species. Network analyses indicated that AM fungal communities in the roots of FM plant species had higher nestedness rank and resource range than networks associated with OM plant species, suggesting that OM plant species are more generalist regarding partner selection and interact with a wider range of fungal partners. Our results suggest that plant mycorrhizal status conveys useful information about the characteristics of AM fungal interaction networks, revealing that plant species consistently associated with AM fungi are less selective towards their fungal partners.Read the free Plain Language Summary for this article on the Journal blog.

We discuss which plant species are likely to become winners, that is achieve the highest global abundance, in changing landscapes, and whether plant-associated microbes play a determining role. Reduction and fragmentation of natural habitats in historic landscapes have led to the emergence of patchy, hybrid landscapes, and novel landscapes where anthropogenic ecosystems prevail. In patchy landscapes, species with broad niches are favoured. Plasticity in the degree of association with symbiotic microbes may contribute to broader plant niches and optimization of symbiosis costs and benefits, by downregulating symbiosis when it is unnecessary and upregulating it when it is beneficial. Plasticity can also be expressed as the switch from one type of mutualism to another, for example from nutritive to defensive mutualism with increasing soil fertility and the associated increase in parasite load. Upon dispersal, wide mutualistic partner receptivity is another facet of symbiont plasticity that becomes beneficial, because plants are not limited by the availability of specialist partners when arriving at new locations. Thus, under conditions of global change, symbiont plasticity allows plants to optimize the activity of mutualistic relationships, potentially allowing them to become winners by maximizing geographic occupancy and local abundance.

Motivation Arbuscular mycorrhizal (AM) fungi are integral to plant nutrient acquisition, carbon cycling, and ecosystem resilience, yet our knowledge of their biogeography is severely limited, especially in the Southern Hemisphere. Australia, despite its landmass and unique geoecological characteristics, has been vastly undersampled, leaving a significant gap in our understanding of AM fungal diversity and distribution. The AusAMF database was created to address this deficiency, the first release comprises AM fungal community data from 610 sampling locations across mainland Australia and Tasmania, collected between 2011 and 2023. Using standardised sampling, DNA extraction, sequencing methods and platforms, this database provides a robust resource for exploring spatial patterns in AM fungal diversity, community composition, and the ecological drivers shaping AM fungal biogeography. The AusAMF database will continue to be updated and maintain standardised approaches to facilitate future research into plant-mycorrhizal interactions, nutrient cycling, and to understand the broader role of AM fungi in ecosystem processes. The data here will provide the foundation for more informed management and conservation efforts in Australia while providing valuable data for global-scale analyses. Main types of variables contained Georeferenced occurrence and abundance of high-throughput amplicon sequences of arbuscular mycorrhizal (AM) fungi. Spatial location and grain Australia. Decimal degrees between 0.000001 – 0.1 resolution. Time period and grain 2011-2023. Month and year of sampling. Major taxa and level of measurement Arbuscular mycorrhizal fungi identified to family, genus, and virtual taxon (VT). Geographic occurrence and amplicon sequence abundance. Software format Interact with data via online application. Dataset available as .csv files and raw sequencing data as .fastq files. ### Competing Interest Statement The authors have declared no competing interest.

Introduction:Traditional approaches to collecting large-scale biodiversity data pose huge logistical and technical challenges. We aimed to assess how a comparatively simple method based on sequencing environmental DNA (eDNA) characterises global variation in plant diversity and community composition compared with data derived from traditional plant inventory methods.Methods:We sequenced a short fragment (P6 loop) of the chloroplast trnL intron from from 325 globally distributed soil samples and compared estimates of diversity and composition with those derived from traditional sources based on empirical (GBIF) or extrapolated plant distribution and diversity data.Results:Large-scale plant diversity and community composition patterns revealed by sequencing eDNA were broadly in accordance with those derived from traditional sources. The success of the eDNA taxonomy assignment, and the overlap of taxon lists between eDNA and GBIF, was greatest at moderate to high latitudes of the northern hemisphere. On average, around half (mean: 51.5% SD 17.6) of local GBIF records were represented in eDNA databases at the species level, depending on the geographic region.Discussion:eDNA trnL gene sequencing data accurately represent global patterns in plant diversity and composition and thus can provide a basis for large-scale vegetation studies. Important experimental considerations for plant eDNA studies include using a sampling volume and design to maximise the number of taxa detected and optimising the sequencing depth. However, increasing the coverage of reference sequence databases would yield the most significant improvements in the accuracy of taxonomic assignments made using the P6 loop of the trnL region.

Anthropogenic disturbances play an increasingly important role in structuring the diversity and functioning of soil organisms such as arbuscular mycorrhizal (AM) fungi. Frequently, multiple land-use practices, which may represent disturbances for AM fungal communities, operate simultaneously in different habitats. It is not known, however, how previous land-use history and specific habitat type influence AM fungal community response to disturbances. We applied mechanical (cutting to stimulate tillage) and chemical (herbicide addition) disturbances to AM fungal communities from meadow and arable field soils. Our results indicated that AM fungal communities from meadows, which previously had experienced mowing, were more species rich than communities from fields that had experienced intensive land-use practices. There were no significant differences, however, in the responses to disturbance of the AM fungal communities from field and meadow soils. We expected mechanical disturbance to promote taxa from the family Glomeraceae which are expected to exhibit a ruderal life-history strategy; instead, the abundance of this family increased in response to chemical disturbance. Simultaneous application of mechanical disturbance and herbicide decreased only the abundance of Diversisporaceae. No AM fungal families increased in abundance when both mechanical and chemical disturbances were applied simultaneously, but all disturbances increased the abundance of culturable AM fungi. Our study demonstrates that although chemical and mechanical forms of disturbance favor different AM fungal families, existing information about family-level characteristics may not adequately characterize the life history strategies of AM fungus species.

EDITORIAL article Front. Plant Sci., 27 September 2023Sec. Plant Symbiotic Interactions Volume 14 - 2023 | https://doi.org/10.3389/fpls.2023.1294388

Our knowledge of microbial biogeography has advanced in recent years, yet we lack knowledge of the global diversity of some important functional groups. Here, we used environmental DNA from 327 globally collected soil samples to investigate the biodiversity patterns of nitrogen-fixing bacteria by focusing on the nifH gene but also amplifying the general prokaryotic 16S SSU region. Globally, N-fixing prokaryotic communities are driven mainly by climatic conditions, with most groups being positively correlated with stable hot or seasonally humid climates. Among soil parameters, pH, but also soil N content were most often shown to correlate with the diversity of N-fixer groups. However, specific groups of N-fixing prokaryotes show contrasting responses to the same variables, notably in Cyanobacteria that were negatively correlated with stable hot climates, and showed a U-shaped correlation with soil pH, contrary to other N-fixers. Also, the non-N-fixing prokaryotic community composition was differentially correlated with the diversity and abundance of N-fixer groups, showing the often-neglected impact of biotic interactions among bacteria.

Species interactions exert important influences on biodiversity and ecosystem stability. In complex natural communities, species interactions have gone beyond pairwise mechanisms, as interactions between two species can be regulated by one or more other species (higher-order species interactions). However, few studies consider higher-order interactions among organisms that are indirectly contacted, particularly under high soil nutrient conditions. Here, we performed a common garden experiment to investigate how natural herbivory (aboveground weevil) and simulated herbivory (leaf clipping) affect plant (Triadica sebifera) interactions with soil antagonists (root-knot nematodes) and mutualists (arbuscular mycorrhizal fungi; AMF) under nitrogen and phosphorus addition. We also tested the effects of nitrogen, phosphorus, and herbivory-stimuli on T. sebifera leaf extrafloral nectary (EFN) production. We found that T. sebifera can compensate for biomass loss caused by clipping or weevil feeding, moreover, high nitrogen availability caused plant biomass to outpace herbivory-stimuli. Plant–antagonist (root-knot nematodes) interactions were not affected by clipping or weevil feeding under ambient nitrogen condition but were reduced by clipping or weevil feeding under high nitrogen supply, however, we did not find the same pattern under phosphorus addition. Aboveground herbivory-stimuli did not affect plant–mutualist (AMF) interactions, whether fertilized or not. In addition, nitrogen addition stimulated plants to secrete more EFN against clipping but did not increase EFN production against weevil feeding. Clipping and weevil feeding exhibited consistent effects on both plant–antagonist (root-knot nematodes) interactions and plant–mutualist (AMF) interactions. These results suggest that aboveground antagonists mainly mitigate belowground plant–antagonist interactions but not affect plant–mutualist interactions, and higher-order species interactions depend on nitrogen addition but not phosphorus addition.

Natural restoration has often been considered an effective measure for rehabilitating degraded ecosystems. However, its impact on the structure and diversity of soil microbial communities, particularly within a salinized grassland during its restoration succession, remains unclear. In this study, we examined the effects of natural restoration on the Shannon-Wiener diversity index, Operational Taxonomic Units (OTU) richness, and structure of the soil microbial community of a sodic-saline grassland in China using high-throughput amplicon sequencing data from representative successional chronosequences. Our results indicated that natural restoration resulted in a significant mitigation of the grassland salinization (pH from 9.31 to 8.32 and electrical conductivity from 393.33 to 136.67 μs·cm-1) and a significant alteration of the soil microbial community structure of the grassland (p < 0.01). However, the effects of natural recovery differed in terms of the abundance and diversity of bacteria and fungi. For example, the relative abundance of the bacterial phyla Acidobacteria increased by 116.45 % in the topsoil and 339.03 % in the subsoil, while that of the fungal phyla Ascomycota decreased by 8.86 % in the topsoil and 30.18 % in the subsoil. There was no significant effect of restoration on bacterial diversity, but fungal diversity increased by 15.02 % in the Shannon-Wiener index and 62.20 % in the OTU richness in the topsoil. Model-selection analysis further corroborated that the alteration of the soil microbial structure by natural restoration may be due to the fact that the bacteria could adapt to the alleviated salinized grassland soil and the fungi could adapt to the improved soil fertility of the grasslands. Overall, our results contribute to an in-depth understanding of the impacts of natural restoration on soil microbial diversity and community structure in salinized grasslands during the long-term successional course. This may also help to apply natural restoration as a greener practice option for managing degraded ecosystems.

Arbuscular mycorrhizal (AM) fungi are a ubiquitous group of plant symbionts, yet processes underlying their global assembly — in particular the roles of dispersal limitation and historical drivers — remain poorly understood. Because earlier studies have reported niche conservatism in AM fungi, we hypothesized that variation in taxonomic community composition (i.e., unweighted by taxon relatedness) should resemble variation in phylogenetic community composition (i.e., weighted by taxon relatedness) which reflects ancestral adaptations to historical habitat gradients. Because of the presumed strong dispersal ability of AM fungi, we also anticipated that the large-scale structure of AM fungal communities would track environmental conditions without regional discontinuity. We used recently published AM fungal sequence data (small‐subunit ribosomal RNA gene) from soil samples collected worldwide to reconstruct global patterns in taxonomic and phylogenetic community variation. The taxonomic structure of AM fungal communities was primarily driven by habitat conditions, with limited regional differentiation, and there were two well-supported clusters of communities — occurring in cold and warm conditions. Phylogenetic structure was driven by the same factors, though all relationships were markedly weaker. This suggests that niche conservatism with respect to habitat associations is weakly expressed in AM fungal communities. We conclude that the composition of AM fungal communities tracks major climatic and edaphic gradients, with the effects of dispersal limitation and historic factors considerably less apparent than those of climate and soil.