How do microbiota associated with an invasive seaweed vary across scales?

Communities are shaped by scale dependent processes. To study the diversity and variation of microbial communities across scales, the invasive and widespread seaweed Agarophyton vermiculophyllum presents a unique opportunity. We characterized pro‐ and eukaryotic communities associated with this holobiont across its known distribution range, which stretches over the northern hemisphere. Our data reveal that community composition and diversity in the holobiont vary at local but also larger geographic scales. While processes acting at the local scale (i.e., within population) are the main structuring drivers of associated microbial communities, changes in community composition also depend on processes acting at larger geographic scales. Interestingly, the largest analysed scale (i.e., native and non‐native ranges) explained variation in the prevalence of predicted functional groups, which could suggest a functional shift in microbiota occurred over the course of the invasion process. While high variability in microbiota at the local scale supports A. vermiculophyllum to be a generalist host, we also identified a number of core taxa. These geographically independent holobiont members imply that cointroduction of specific microbiota may have additionally promoted the invasion process.     

Arbuscular mycorrhizal fungal communities in plant roots are not random assemblages

We investigated whether arbuscular mycorrhizal fungal (AMF) communities in plant roots are random subsets of the local taxon pool or whether they reflect the action of certain community assembly rules. We studied AMF small subunit rRNA gene sequence groups in the roots of plant individuals belonging to 11 temperate forest understorey species. Empirical data were compared with null models assuming random association. Distinct fungal species pools were present in young and old successional forest. In both forest types, the richness of plant-AMF associations was lower than expected by chance, indicating a degree of partner selectivity. AMF communities were generally not characteristic of individual plant species, but those associated with ecological groups of plant species - habitat generalists and forest specialists - were nonrandom subsets of the available pool of fungal taxa and differed significantly from each other. Moreover, these AMF communities were the least distinctive in spring, but developed later in the season. Comparison with a global database showed that generalist plants tend to associate with generalist AMF. Thus, the habitat range of the host and a possible interaction with season played a role in the assembly of AMF communities in individual plant root systems.     

Do invasive plants structure microbial communities to accelerate decomposition in intermountain grasslands?

Invasive plants are often associated with greater productivity and soil nutrient availabilities, but whether invasive plants with dissimilar traits change decomposer communities and decomposition rates in consistent ways is little known. We compared decomposition rates and the fungal and bacterial communities associated with the litter of three problematic invaders in intermountain grasslands; cheatgrass (Bromus tectorum), spotted knapweed (Centaurea stoebe) and leafy spurge (Euphorbia esula), as well as the native bluebunch wheatgrass (Pseudoroegneria spicata). Shoot and root litter from each plant was placed in cheatgrass, spotted knapweed, and leafy spurge invasions as well as remnant native communities in a fully reciprocal design for 6 months to see whether decomposer communities were species‐specific, and whether litter decomposed fastest when placed in a community composed of its own species (referred to hereafter as home‐field advantage–HFA). Overall, litter from the two invasive forbs, spotted knapweed and leafy spurge, decomposed faster than the native and invasive grasses, regardless of the plant community of incubation. Thus, we found no evidence of HFA. T‐RFLP profiles indicated that both fungal and bacterial communities differed between roots and shoots and among plant species, and that fungal communities also differed among plant community types. Synthesis. These results show that litter from three common invaders to intermountain grasslands decomposes at different rates and cultures microbial communities that are species‐specific, widespread, and persistent through the dramatic shifts in plant communities associated with invasions.     

Changes in arbuscular mycorrhizal fungal communities during invasion by an exotic invasive plant

Exotic invasive plants can show strong plant–soil feedback responses, but little is known about time scales for significant changes in soil microbial communities to occur after invasion. Previous work has suggested that plant invasions can modify arbuscular mycorrhizal (AM) fungal community structure. However, there is a lack of understanding about how long it takes for these changes to develop. To test this we investigated temporal changes in AM fungal communities colonising the invasive plant Vincetoxicum rossicum (Apocynaceae). We hypothesised that AM fungal community structure would change in a particular direction during the invasion process. We collected soil from two sites with a long history of invasion by this plant, with each site having paired invaded and uninvaded plots. Soil from these plots was used in a glasshouse experiment to characterise AM fungal community structure in the roots of V. rossicum at different times throughout a simulated growing season. AM fungal community structure differed between invaded and uninvaded plots. However, contrasting with our hypothesis, AM fungal communities colonising V. rossicum growing in soil from uninvaded plots did not change towards those in plants growing in previously invaded soil. Our data suggest that changes to AM fungal communities in the presence of V. rossicum require longer than the first growing season after establishment to develop.     

AM fungal communities inhabiting the roots of submerged aquatic plant <Emphasis Type="Italic">Lobelia dortmanna</Emphasis> are diverse and include a high proportion of novel taxa

While the arbuscular mycorrhizal (AM) symbiosis is known to be widespread in terrestrial ecosystems, there is growing evidence that aquatic plants also form the symbiosis. It has been suggested that symbiosis with AM fungi may represent an important adaptation for isoëtid plants growing on nutrient-poor sediments in oligotrophic lakes. In this study, we address AM fungal root colonization intensity, richness and community composition (based on small subunit (SSU) ribosomal RNA (rRNA) gene sequencing) in five populations of the isoëtid plant species Lobelia dortmanna inhabiting oligotrophic lakes in Southern Sweden. We found that the roots of L. dortmanna hosted rich AM fungal communities and about 15 % of the detected molecular taxa were previously unrecorded. AM fungal root colonization intensity and taxon richness varied along an environmental gradient, being higher in oligotrophic and lower in mesotrophic lakes. The overall phylogenetic structure of this aquatic fungal community differed from that described in terrestrial systems: The roots of L. dortmanna hosted more Archaeosporaceae and fewer Glomeraceae taxa than would be expected based on global data from terrestrial AM fungal communities.     

Mycorrhizal associations of an invasive tree are enhanced by both genetic and environmental mechanisms

Biotic interactions involving exotic plants in their introduced ranges may differ from those of co‐occurring plant species and from interactions in their native ranges. When interactions are less negative, or more positive compared to native plant species, this may increase invasion success, and differences among ranges may cause changes in exotic plant traits. Here, we investigated arbuscular mycorrhizae (AM) associated with Triadica sebifera seedlings from populations in native (China) and introduced ranges (US) and with seedlings from US and China species within three co‐occurring genera (Liquidambar, Ulmus, Celtis) grown in multiple common gardens in both ranges. No general pattern of higher or lower AM colonization was found in the introduced range for China and US Celtis, Liquidambar, or Ulmus species. However, AM colonization was significantly higher for Triadica than for other genera, particularly in the introduced range, suggesting AM may improve Triadica's invasion success. Triadica AM colonization was higher in US than China gardens, decreased with increasing soil nitrogen in China, but was independent of soil nitrogen in the US. This might reflect a different effect of soil fertility on this mutualism among ranges. Introduced Triadica populations had higher AM colonization than native populations, particularly in US gardens, implying a possible advantage from greater AM association in the introduced range. This is the first field study demonstrating post‐introduction changes in mycorrhizal colonization of an invasive species. It indicates that there are ecological and evolutionary components to the effect of positive interactions on plant invasions.     

Effects of generalist herbivory on resistance and resource allocation by the invasive plant,Phytolacca americana

Successful invasions by exotic plants are often attributed to a loss of co‐evolved specialists and a re‐allocation of resources from defense to growth and reproduction. However, invasive plants are rarely completely released from insect herbivory because they are frequently attacked by generalists in their introduced ranges. The novel generalist community may also affect the invasive plant's defensive strategies and resource allocation. Here, we tested this hypothesis using American pokeweed (Phytolacca americana L.), a species that has become invasive in China, which is native to North America. We examined resistance, tolerance, growth and reproduction of plant populations from both China and the USA when plants were exposed to natural generalist herbivores in China. We found that leaf damage was greater for invasive populations than for native populations, indicating that plants from invasive ranges had lower resistance to herbivory than those from native ranges. A regression of the percentage of leaf damage against mass showed that there was no significant difference in tolerance between invasive and native populations, even though the shoot, root, fruit and total mass were larger for invasive populations than for native populations. These results suggest that generalist herbivores are important drivers mediating the defensive strategies and resource allocation of the invasive American pokeweed.     

Arbuscular mycorrhizal communities in tropical forests are affected by host tree species and environment

Arbuscular mycorrhizal (AM) fungi are mutualists with plant roots that are proposed to enhance plant community diversity. Models indicate that AM fungal communities could maintain plant diversity in forests if functionally different communities are spatially separated. In this study we assess the spatial and temporal distribution of the AM fungal community in a wet tropical rainforest in Costa Rica. We test whether distinct fungal communities correlate with variation in tree life history characteristics, with host tree species, and the relative importance of soil type, seasonality and rainfall. Host tree species differ in their associated AM fungal communities, but differences in the AM community between hosts could not be generalized over life history groupings of hosts. Changes in the relative abundance of a few common AM fungal species were the cause of differences in AM fungal communities for different host tree species instead of differences in the presence and absence of AM fungal species. Thus, AM fungal communities are spatially distinguishable in the forest, even though all species are widespread. Soil fertility ranging between 5 and 9 Mg/ha phosphorus did not affect composition of AM fungal communities, although sporulation was more abundant in lower fertility soils. Sampling soils over seasons revealed that some AM fungal species sporulate profusely in the dry season compared to the rainy season. On one host tree species sampled at two sites with vastly different rainfall, relative abundance of spores from Acaulospora was lower and that of Glomus was relatively higher at the site with lower and more seasonal rainfall.     

Foraging speed and precision of arbuscular mycorrhizal fungi under field conditions: An experimental approach

To better understand the ecology of arbuscular mycorrhizal (AM) symbiosis, we need to measure functional traits of individual fungal virtual taxa under field conditions. The efficiency of AM fungi in locating nutrient‐rich patches in soil space is one of their central traits in this symbiotic relationship. We used plots of a long‐term field experiment in grassland with manipulated functional group composition of host plant community to establish ingrowth patches with substrate free of roots and fungi and with varying nutrient availability. Comparison of the original AM fungal community before patch creation with that present 9 weeks after patch establishment enabled us to estimate relative hyphal foraging speed for 41 fungal taxa, and a comparison of the fungal community in neighbouring patches differing in nutrient availability provided estimates of hyphal foraging precision for 22 taxa. Members of two dominant fungal families, Glomeraceae and Claroideoglomeraceae, differed in their foraging speed and precision. Glomeraceae taxa responded more slowly, but with a higher focus on enriched patches. We further demonstrated the usefulness of the obtained fungal functional traits by testing the differences between grass and dicotyledonous plant hosts using a data set obtained in another experiment at the same plots. Grass species hosted AM fungal communities with higher foraging speed, but lower foraging precision than the dicotyledonous species. Our study results support the use of field experiments for measuring comparative characteristics of AM fungi, which are highly elusive (or misrepresented) under controlled conditions.     

Increasing flavonoid concentrations in root exudates enhance associations between arbuscular mycorrhizal fungi and an invasive plant

Many invasive plants have enhanced mutualistic arbuscular mycorrhizal (AM) fungal associations, however, mechanisms underlying differences in AM fungal associations between introduced and native populations of invasive plants have not been explored. Here we test the hypothesis that variation in root exudate chemicals in invasive populations affects AM fungal colonization and then impacts plant performance. We examined flavonoids (quercetin and quercitrin) in root exudates of native and introduced populations of the invasive plant Triadica sebifera and tested their effects on AM fungi and plant performance. We found that plants from introduced populations had higher concentrations of quercetin in root exudates, greater AM fungal colonization and higher biomass. Applying root exudates more strongly increased AM fungal colonization of target plants and AM fungal spore germination when exudate donors were from introduced populations. The role of root exudate chemicals was further confirmed by decreased AM fungal colonization when activated charcoal was added into soil. Moreover, addition of quercetin into soil increased AM fungal colonization, indicating quercetin might be a key chemical signal stimulating AM fungal associations. Together these results suggest genetic differences in root exudate flavonoids play an important role in enhancing AM fungal associations and invasive plants’ performance, thus considering root exudate chemicals is critical to unveiling mechanisms governing shifting plant-soil microbe interactions during plant invasions.Subject terms: Population dynamics, Community ecology, Plant ecology     

Complex interactions between spatial pattern of resident species and invasiveness of newly arriving species affect invasibility

Understanding the factors that affect establishment success of new species in established communities requires the study of both the ability of new species to establish and community resistance. Spatial pattern of species within a community can affect plant performance by changing the outcome of inter-specific competition, and consequently community invasibility. We studied the effects of spatial pattern of resident plant communities on fitness of genotypes from the native and introduced ranges of two worldwide invasive species, Centaurea stoebe and Senecio inaequidens, during their establishment stage. We experimentally established artificial plant mixtures with 4 or 8 resident species in intra-specifically aggregated or random spatial patterns, and added seedlings of genotypes from the native and introduced ranges of the two target species. Early growth of both S. inaequidens and C. stoebe was higher in aggregated than randomly assembled mixtures. However, a species-specific interaction between invasiveness and invasibility highlighted more complex patterns. Genotypes from native and introduced ranges of S. inaequidens showed the same responses to spatial pattern. By contrast, genotypes from the introduced range of C. stoebe did not respond to spatial pattern whereas native ones did. Based on phenotypic plasticity, we argue that the two target species adopted different strategies to deal with the spatial pattern of the resident plant community. We show that effects of spatial pattern of the resident community on the fitness of establishing species may depend on the diversity of the recipient community. Our results highlight the need to consider the interaction between invasiveness and invasibility in order to increase our understanding of invasion success.     

The effects of arbuscular mycorrhizal (AM) fungal and garlic mustard introductions on native AM fungal diversity

Introduced, non-native organisms are of global concern, because biological invasions can negatively affect local communities. Arbuscular mycorrhizal (AM) fungal communities have not been well studied in this context. AM fungi are abundant in most soils, forming symbiotic root-associations with many plant species. Commercial AM fungal inocula are increasingly spread worldwide, because of potentially beneficial effects on plant growth. In contrast, some invasive plant species, such as the non-mycorrhizal Alliaria petiolata, can negatively influence AM fungi. In a greenhouse study we examined changes in the structure of a local Canadian AM fungal community in response to inoculation by foreign AM fungi and the manipulated presence/absence of A. petiolata. We expected A. petiolata to have a stronger effect on the local AM fungal community than the addition of foreign AM fungal isolates. Molecular analyses indicated that inoculated foreign AM fungi successfully established and decreased molecular diversity of the local AM fungal community in host roots. A. petiolata did not affect molecular diversity, but reduced AM fungal growth in the greenhouse study and in a in vitro assay. Our findings suggest that both introduced plants and exotic AM fungi can have negative impacts on local AM fungi.     

Unique arbuscular mycorrhizal fungal communities uncovered in date palm plantations and surrounding desert habitats of Southern Arabia

The main objective of this study was to shed light on the previously unknown arbuscular mycorrhizal fungal (AMF) communities in Southern Arabia. We explored AMF communities in two date palm (Phoenix dactylifera) plantations and the natural vegetation of their surrounding arid habitats. The plantations were managed traditionally in an oasis and according to conventional guidelines at an experimental station. Based on spore morphotyping, the AMF communities under the date palms appeared to be quite diverse at both plantations and more similar to each other than to the communities under the ruderal plant, Polygala erioptera, growing at the experimental station on the dry strip between the palm trees, and to the communities uncovered under the native vegetation (Zygophyllum hamiense, Salvadora persica, Prosopis cineraria, inter-plant area) of adjacent undisturbed arid habitat. AMF spore abundance and species richness were higher under date palms than under the ruderal and native plants. Sampling in a remote sand dune area under Heliotropium kotschyi yielded only two AMF morphospecies and only after trap culturing. Overall, 25 AMF morphospecies were detected encompassing all study habitats. Eighteen belonged to the genus Glomus including four undescribed species. Glomus sinuosum, a species typically found in undisturbed habitats, was the most frequently occurring morphospecies under the date palms. Using molecular tools, it was also found as a phylogenetic taxon associated with date palm roots. These roots were associated with nine phylogenetic taxa, among them eight from Glomus group A, but the majority could not be assigned to known morphospecies or to environmental sequences in public databases. Some phylogenetic taxa seemed to be site specific. Despite the use of group-specific primers and efficient trapping systems with a bait plant consortium, surprisingly, two of the globally most frequently found species, Glomus intraradices and Glomus mosseae, were not detected neither as phylogenetic taxa in the date palm roots nor as spores under the date palms, the intermediate ruderal plant, or the surrounding natural vegetation. The results highlight the uniqueness of AMF communities inhabiting these diverse habitats exposed to the harsh climatic conditions of Southern Arabia.     

Selective alteration of soil food web components by invasive giant goldenrod Solidago gigantea in two distinct habitat types

Apart from relatively well‐studied aboveground effects, invasive plant species will also impact the soil food web. So far, most research has been focusing on primary decomposers, while studies on effects at higher trophic levels are relatively scarce. Giant goldenrod Solidago gigantea, native to North America, is a widespread and common invasive species in most European countries. We investigated its impact on plant communities and on multiple trophic levels of the soil food web in two contrasting habitats: riparian zones and semi‐natural grasslands. In 30 pairs of invaded and uninvaded plots, floristic composition, pH, fungal biomass and the densities of 11 nematode taxa were determined by using a quantitative PCR‐based method. In the two habitats, the invader outcompeted both rare and dominant plant species. Belowground, S. gigantea invasion reduced pH, increased overall fungal biomass as well as the density of a single lineage of fungivorous nematodes, the family Aphelenchoididae. The densities of two other, phylogenetically distinct lineages of fungivorous nematodes, Aphelenchidae and Diphtherophoridae, were unaffected by the local increase in fungal biomass. Apparently this plant species induces a local asymmetric boost of the fungal community, and only Aphelenchoididae were able to benefit from this invader‐induced change. The alternative explanation – the results are explained by a subtle, S. gigantea‐induced 0.1–0.2 units decrease of pH – seems unlikely, as pH optima for nematode taxa are relatively broad. Thus, apart from readily observable aboveground effects, the invasive plant species S. gigantea affects fungal biomass as well as a specific part of the fungivorous nematode community in a soil type‐independent manner.     

Local adaptation to soil hypoxia determines the structure of an arbuscular mycorrhizal fungal community in roots from natural CO₂ springs

The processes responsible for producing and maintaining the diversity of natural arbuscular mycorrhizal (AM) fungal communities remain largely unknown. We used natural CO(2) springs (mofettes), which create hypoxic soil environments, to determine whether a long-term, directional, abiotic selection pressure could change AM fungal community structure and drive the selection of particular AM fungal phylotypes. We explored whether those phylotypes that appear exclusively in hypoxic soils are local specialists or widespread generalists able to tolerate a range of soil conditions. AM fungal community composition was characterized by cloning, restriction fragment length polymorphism typing, and the sequencing of small subunit rRNA genes from roots of four plant species growing at high (hypoxic) and low (control) geological CO(2) exposure. We found significant levels of AM fungal community turnover (β diversity) between soil types and the numerical dominance of two AM fungal phylotypes in hypoxic soils. Our results strongly suggest that direct environmental selection acting on AM fungi is a major factor regulating AM fungal communities and their phylogeographic patterns. Consequently, some AM fungi are more strongly associated with local variations in the soil environment than with their host plant's distribution.     

Adaptation of plant‐mycorrhizal interactions to moisture availability in prairie restoration

The strength and direction of plant response to inoculation with arbuscular mycorrhizal fungi (AM fungi) is dependent on both abiotic and biotic contexts, often generating patterns of AM fungal mediation of plant adaptation. However, knowledge of plant‐community level effects of these interactions in grassland restoration is limited. We conducted a field inoculation experiment by inoculating five plant species native to a drier prairie and five plant species native to a moister prairie with mycorrhizal fungal communities from each prairie type. Species were paired by genus or family to account for phylogenetic effects. The inoculated plants were transplanted to study plots seeded with a restoration seed mix. Plots were manipulated to create either moister or drier conditions similar to environments of the plant species and mycorrhizal communities. In both transplanted and seeded plant species, we found that only drier prairie‐range species benefited from moisture‐regime matched AM fungal inoculum. Other seeded prairie plant species demonstrated a negative response to inoculation, likely due to the earlier successional stage of these species. Additionally, nonseeded plants benefited from inoculation in different ways: native nonseeded plants had highest cover with drier prairie inoculum in drier conditions, while nonnative plants had highest cover with moister prairie‐origin inoculum. These results suggest that use of local AM fungi may be particularly important in restorations at drier sites, even at relatively small differences in moisture availability. Further, specific knowledge of relative responsiveness of seeded plant species and nonseeded plant species to AM fungal inoculation will be useful in planning restorations.     

Species diversity reduces invasion success in pathogen‐regulated communities

The loss of natural enemies is thought to explain why certain invasive species are so spectacularly successful in their introduced range. However, if losing natural enemies leads to unregulated population growth, this implies that native species are themselves normally subject to natural enemy regulation. One possible widespread mechanism of natural enemy regulation is negative soil feedbacks, in which resident species growing on home soils are disadvantaged because of a build‐up of species‐specific soil pathogens. Here we construct simple models in which pathogens cause resident species to suffer reduced competitive ability on home soils and consider the consequences of such pathogen regulation for potential invading species. We show that the probability of successful invasion and its timescale depend strongly on the competitive ability of the invader on resident soils, but are unaffected by whether or not the invader also suffers reduced competitive ability on home soils (i.e. pathogen regulation). This is because, at the start of an invasion, the invader is rare and hence mostly encounters resident soils. However, the lack of pathogen regulation does allow the invader to achieve an unusually high population density. We also show that increasing resident species diversity in a pathogen‐regulated community increases invasion resistance by reducing the frequency of home‐site encounters. Diverse communities are more resistant to invasion than monocultures of the component species: they preclude a greater range of potential invaders, slow the timescale of invasion and reduce invader population size. Thus, widespread pathogen regulation of resident species is a potential explanation for the empirical observation that diverse communities are more invasion resistant.     

Biogeographical comparison of the arthropod herbivore communities associated with Lepidium draba in its native, expanded and introduced ranges

Aim To examine the composition and structure of the arthropod community on the invasive weed Lepidium draba in its native, expanded and introduced ranges, in order to elucidate the lack of a biotic constraint that may facilitate invasion. Location Europe and western North America. Methods Identical sampling protocols were used to collect data from a total of 35 populations of L. draba in its native (Eastern European), expanded (Western European) and introduced (western US) ranges. A bootstrapping analysis was used to compare herbivore richness, diversity and evenness among the regions. Core species groups (monophages, oligophages and polyphages) on the plant were defined and their abundances and host utilization patterns described. Results Species richness was greatest in the native range, while species diversity and evenness were similar in the native and expanded range, but significantly greater than in the introduced range of L. draba. Specialist herbivore abundance was greater in the native and expanded compared with the introduced range. Oligophagous Brassicaceae‐feeders were equally abundant in all three ranges, and polyphagous herbivore abundance was significantly greater in the introduced range. Overall herbivore abundance was greater in the introduced range. Host utilization was more complete in the two European ranges due to monophagous herbivores that do not exist in the introduced range. Root feeders and gall formers were completely absent from the introduced range, which was dominated by generalist sap‐sucking herbivores. However, one indigenous stem‐mining weevil, Ceutorhynchus americanus, occurred on L. draba in the introduced range. Main conclusions This is, to our knowledge, the first study documenting greater herbivore abundance on an invasive weed in its introduced, compared with its native, range. However, greater abundance does not necessarily translate to greater impact. We argue that, despite the greater total herbivore abundance in the introduced range, differences in the herbivore community structure (specialist vs. generalist herbivory) may contribute to the invasion success of L. draba in the western USA.     

Soil nutritional status, not inoculum identity, primarily determines the effect of arbuscular mycorrhizal fungi on the growth of Knautia arvensis plants

Arbuscular mycorrhizal (AM) symbiosis is among the factors contributing to plant survival in serpentine soils characterised by unfavourable physicochemical properties. However, AM fungi show a considerable functional diversity, which is further modified by host plant identity and edaphic conditions. To determine the variability among serpentine AM fungal isolates in their effects on plant growth and nutrition, a greenhouse experiment was conducted involving two serpentine and two non-serpentine populations of Knautia arvensis plants grown in their native substrates. The plants were inoculated with one of the four serpentine AM fungal isolates or with a complex AM fungal community native to the respective plant population. At harvest after 6-month cultivation, intraradical fungal development was assessed, AM fungal taxa established from native fungal communities were determined and plant growth and element uptake evaluated. AM symbiosis significantly improved the performance of all the K. arvensis populations. The extent of mycorrhizal growth promotion was mainly governed by nutritional status of the substrate, while the effect of AM fungal identity was negligible. Inoculation with the native AM fungal communities was not more efficient than inoculation with single AM fungal isolates in any plant population. Contrary to the growth effects, a certain variation among AM fungal isolates was revealed in terms of their effects on plant nutrient uptake, especially P, Mg and Ca, with none of the AM fungi being generally superior in this respect. Regardless of AM symbiosis, K. arvensis populations significantly differed in their relative nutrient accumulation ratios, clearly showing the plant’s ability to adapt to nutrient deficiency/excess.