Interactions between communities of plants and arbuscular mycorrhizal (AM) fungi shape fundamental ecosystem properties. Experimental evidence suggests that compositional changes in plant and AM ...fungal communities should be correlated, but empirical data from natural ecosystems are scarce. We investigated the dynamics of covariation between plant and AM fungal communities during three stages of grassland succession, and the biotic and abiotic factors shaping these dynamics.
Plant communities were characterised using vegetation surveys. AM fungal communities were characterised by 454-sequencing of the small subunit rRNA gene and identification against the AM fungal reference database MaarjAM. AM fungal abundance was estimated using neutral-lipid fatty acids (NLFAs).
Multivariate correlation analysis (Procrustes) revealed a significant relationship between plant and AM fungal community composition. The strength of plant–AM fungal correlation weakened during succession following cessation of grassland management, reflecting changes in the proportion of plants exhibiting different AM status. Plant–AM fungal correlation was strong when the abundance of obligate AM plants was high, and declined as the proportion of facultative AM plants increased.
We conclude that the extent to which plants rely on AM symbiosis can determine how tightly communities of plants and AM fungi are interlinked, regulating community assembly of both symbiotic partners.
Abstract
Wetland soils are the greatest source of nitrous oxide (N
2
O), a critical greenhouse gas and ozone depleter released by microbes. Yet, microbial players and processes underlying the N
2
O ...emissions from wetland soils are poorly understood. Using in situ N
2
O measurements and by determining the structure and potential functional of microbial communities in 645 wetland soil samples globally, we examined the potential role of archaea, bacteria, and fungi in nitrogen (N) cycling and N
2
O emissions. We show that N
2
O emissions are higher in drained and warm wetland soils, and are correlated with functional diversity of microbes. We further provide evidence that despite their much lower abundance compared to bacteria, nitrifying archaeal abundance is a key factor explaining N
2
O emissions from wetland soils globally. Our data suggest that ongoing global warming and intensifying environmental change may boost archaeal nitrifiers, collectively transforming wetland soils to a greater source of N
2
O.
1 Arbuscular mycorrhizal (AM) fungi are obligate root symbionts that are present in most terrestrial ecosystems and have roles in plant mineral nutrition, carbon cycling and biotic interactions. In ...this work, 26 publications were surveyed that report on the occurrence of natural root-colonizing AM fungi identified using rDNA region sequences. A total of 52 host plant species were investigated. Sixteen publications provided data enabling a comparison to be made of AM fungal taxon richness and community composition across 36 host plant species and 25 locations. Ninety-five fungal taxa (small subunit rRNA gene sequence types) were involved, 49 of which were recorded from at least two study sites, and 65 from more than one host plant species. 2 The number of AM fungal taxa per host plant species differed between habitat types: a significantly higher richness was found in tropical forests (18.2 fungal taxa per plant species), followed by grasslands (8.3), temperate forests (5.6) and habitats under anthropogenic influence (arable fields and polluted sites, 5.2). 3 AM fungal communities exhibit differing compositions in broadly defined habitat types: tropical forests, temperate forests and habitats under anthropogenic influence. Grassland locations around the world host heterogeneous AM fungal communities. 4 A number of AM fungi had a global distribution, including sequence types related to the Glomus intraradiceslfasciculatum group, G. mosseae, G. sp. UY1225 and G. hoi, as well as the Glomus and Scutellospora types of unknown taxonomic affiliation. Widespread taxa occur in both natural and anthropogenic (disturbed) habitats, and may show high local abundance. However, about 50% of taxa have been recorded from only a single site. 5 The current global analysis of AM fungal communities suggests that soil microorganisms may exhibit different distribution patterns, resulting in a high variability of taxon richness and composition between particular ecosystems.
Although experiments show a positive association between vascular plant and arbuscular mycorrhizal fungal (AMF) species richness, evidence from natural ecosystems is scarce. Furthermore, there is ...little knowledge about how AMF richness varies with belowground plant richness and biomass. We examined relationships among AMF richness, above‐ and belowground plant richness, and plant root and shoot biomass in a native North American grassland. Root‐colonizing AMF richness and belowground plant richness were detected from the same bulk root samples by 454‐sequencing of the AMF SSU rRNA and plant trnL genes. In total we detected 63 AMF taxa. Plant richness was 1.5 times greater belowground than aboveground. AMF richness was significantly positively correlated with plant species richness, and more strongly with below‐ than aboveground plant richness. Belowground plant richness was positively correlated with belowground plant biomass and total plant biomass, whereas aboveground plant richness was positively correlated only with belowground plant biomass. By contrast, AMF richness was negatively correlated with belowground and total plant biomass. Our results indicate that AMF richness and plant belowground richness are more strongly related with each other and with plant community biomass than with the plant aboveground richness measures that have been almost exclusively considered to date.
Processes controlling the assembly of microorganism communities are poorly understood. In taxonomic groups where many organisms are only described from environmental DNA, phylogenetic relationships ...may provide a proxy for functional attributes. We used a null model approach to compare the phylogenetic diversity of arbuscular mycorrhizal (AM) fungal communities coexisting within the roots of plant individuals sampled worldwide. Parallel null models were constructed using taxon pools that were filtered according to some or all of spatial scale, ecosystem type and host plant identity. This allowed us to assess the importance of individual ecological gradients in shaping phylogenetic diversity and to identify potential mechanisms. In general, coexisting fungi were more phylogenetically clustered than the random communities defined by null models. However, clustering increased when null models incorporated large spatial scales, indicating that communities are assembled according to the dispersal ability of fungal taxa. Clustering also increased when null models incorporated a variety of ecosystems or host plant species, indicating effects of habitat filtering and mutualist partner selection at wide and local scales, respectively. We did not record phylogenetic overdispersion among coexisting fungi, providing no support for a role of limiting similarity in structuring AM fungal communities. However, the existence of significant clustering even in comparison with the finest-scale null model indicates that, in addition to larger-scale deterministic and neutral processes, the symbiosis may be further influenced by genotypic selectivity or stochastic processes at very small scales.
•Phylogenetic relationships may represent functional attributes in soil microbes.•Here, phylogenetic diversity is used to assess community assembly in AMF.•Nested null models are used to identify individual processes influencing assembly.•Dispersal limitation, habitat filtering and mutualist selection all play roles.•However, very small scale deterministic or stochastic processes are also important.
Despite the important ecosystem role played by arbuscular mycorrhizal fungi (AMF), little is known about spatial and temporal variation in soil AMF communities. We used pyrosequencing to characterise ...AMF communities in soil samples (n = 44) from a natural forest ecosystem. Fungal taxa were identified by BLAST matching of reads against the MaarjAM database of AMF SSU rRNA gene diversity. Sub-sampling within our dataset and experimental shortening of a set of long reads indicated that our approaches to taxonomic identification and diversity analysis were robust to variations in pyrosequencing read length and numbers of reads per sample. Different forest plots (each 10 × 10 m and separated from one another by 30 m) contained significantly different soil AMF communities, and the pairwise similarity of communities decreased with distance up to 50 m. However, there were no significant changes in community composition between different time points in the growing season (May-September). Spatial structure in soil AMF communities may be related to the heterogeneous vegetation of the natural forest study system, while the temporal stability of communities suggests that AMF in soil represent a fairly constant local species pool from which mycorrhizae form and disband during the season.
Predominant frameworks for understanding plant ecology have an aboveground bias that neglects soil micro-organisms. This is inconsistent with recent work illustrating the importance of soil microbes ...in terrestrial ecology. Microbial effects have been incorporated into plant community dynamics using ideas of niche modification and plant–soil community feedbacks. Here, we expand and integrate qualitative conceptual models of plant niche and feedback to explore implications of microbial interactions for understanding plant community ecology. At the same time we review the empirical evidence for these processes. We also consider common mycorrhizal networks, and propose that these are best interpreted within the feedback framework. Finally, we apply our integrated model of niche and feedback to understanding plant coexistence, monodominance and invasion ecology.
Abstract
Arbuscular mycorrhizal (AM) fungi play an important role in ecosystems, but little is known about how soil AM fungal community composition varies in relation to habitat type and land-use ...intensity. We molecularly characterized AM fungal communities in soil samples (n = 88) from structurally open (permanent grassland, intensive and sustainable agriculture) and forested habitats (primeval forest and spruce plantation). The habitats harboured significantly different AM fungal communities, and there was a broad difference in fungal community composition between forested and open habitats, the latter being characterized by higher average AM fungal richness. Within both open and forest habitats, intensive land use significantly influenced community composition. There was a broad difference in the phylogenetic structure of AM fungal communities between mechanically disturbed and nondisturbed habitats. Taxa from Glomeraceae served as indicator species for the nondisturbed habitats, while taxa from Archaeosporaceae, Claroideoglomeraceae and Diversisporaceae were indicators for the disturbed habitats. The distribution of these indicator taxa among habitat types in the MaarjAM global database of AM fungal diversity was in accordance with their local indicator status.
By analysing AM fungal DNA in soil from different habitats, its shown that forested and open habitats harbour different fungal communities, while disturbance changes the phylogenetic structure of fungal communities.
By analysing AM fungal DNA in soil from different habitats, its shown that forested and open habitats harbour different fungal communities, while disturbance changes the phylogenetic structure of fungal communities.
Many studies have shown plant species' dispersal distances to be strongly related to life-history traits, but how well different traits can predict dispersal distances is not yet known. We used ...cross-validation techniques and a global data set (576 plant species) to measure the predictive power of simple plant traits to estimate species' maximum dispersal distances. Including dispersal syndrome (wind, animal, ant, ballistic, and no special syndrome), growth form (tree, shrub, herb), seed mass, seed release height, and terminal velocity in different combinations as explanatory variables we constructed models to explain variation in measured maximum dispersal distances and evaluated their power to predict maximum dispersal distances. Predictions are more accurate, but also limited to a particular set of species, if data on more specific traits, such as terminal velocity, are available. The best model (
R
2
= 0.60) included dispersal syndrome, growth form, and terminal velocity as fixed effects. Reasonable predictions of maximum dispersal distance (
R
2
= 0.53) are also possible when using only the simplest and most commonly measured traits; dispersal syndrome and growth form together with species taxonomy data. We provide a function (dispeRsal) to be run in the software package R. This enables researchers to estimate maximum dispersal distances with confidence intervals for plant species using measured traits as predictors. Easily obtainable trait data, such as dispersal syndrome (inferred from seed morphology) and growth form, enable predictions to be made for a large number of species.
Macroecology of biodiversity disentangles local and regional drivers of biodiversity by exploring large-scale biodiversity relationships with environmental or biotic gradients, generalizing local ...biodiversity relationships across regions, or comparing biodiversity patterns among species groups. A macroecological perspective is also important at local scales: a full understanding of local biodiversity drivers, including human impact, demands that regional processes be taken into account. This requires knowledge of which species could inhabit a site (the species pool), including those that are currently absent (dark diversity). Macroecology of biodiversity is currently advancing quickly owing to an unprecedented accumulation of biodiversity data, new sampling techniques and analytical methods, all of which better equip us to face current and future challenges in ecology and biodiversity conservation.
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