Spore Community Research Articles

Effects of arbuscular mycorrhizal fungi in the rhizosphere of two olive (Olea europaea) varieties Arbequina and Barnea under water deficit conditions.

One strategy to improve olive (Olea europaea ) tree drought tolerance is through the symbiosis of arbuscular mycorrhizal fungi (AMF), which helps alleviate water deficit through a combination of morphophysiological effects. Cuttings of olive varieties Arbequina (A) and Barnea (B) were grown with (+AMF) or without (-AMF) inoculum in the olive grove rhizosphere soil. One year after establishment, pots were exposed to four different water regimes: (1) control (100% of crop evapotranspiration); (2) short-period drought (20days); (3) long-period drought (25days); and (4) rewatering (R). To evaluate the influence of AMF on tolerance to water stress, stem water potential, stomatal conductance and the biomarkers for water deficit malondialdehyde, proline, soluble sugars, phenols, and flavonoids were evaluated at the end of the irrigation regimes. Stem water potential showed higher values in A(+) and B(+) in all water conditions, and the opposite was true for stomatal conductance. For proline and soluble sugars, the stem water potential trend is repeated with some exceptions. AMF inoculum spore communities from A(+ and -) and B(+ and -) were characterised at the morphospecies level in terms of richness and abundance. Certain morphospecies were identified as potential drought indicators. These results highlight that the benefits of symbiotic relationships between olive and native AMF can help to mitigate the effects of abiotic stress in soils affected by drought.

Fire season and time since fire determine arbuscular mycorrhizal fungal trait responses to fire

Background and aimsArbuscular mycorrhizal (AM) fungi are common mutualists in grassland and savanna systems that are adapted to recurrent fire disturbance. This long-term adaptation to fire means that AM fungi display disturbance associated traits which should be useful for understanding environmental and seasonal effects on AM fungal community assembly.MethodsIn this work, we evaluated how fire effects on AM fungal spore traits and community composition vary with fire season (Fall vs. Spring) and time since fire. We tested this by analyzing AM fungal spore traits (e.g., colorimetric, sporulation, and size) from a fire regime experiment.ResultsImmediately following Fall and Spring fires, spore pigmentation darkened (became less hyaline); however, this trait response was not linked to fire driven changes in spore community composition and likely implies a plastic spore pigmentation response to fire. Six months after Fall fires, spores in burned plots were lower in volume, produced less color rich pigment, and had higher sporulation rates, and these differences in spore traits were associated with shifts in AM fungal spore communities demonstrating environmental filtering.ConclusionFire drove plastic and longer-term changes in AM fungal spore traits and community assembly that varied with fire season (stronger effects in Fall) and time since fire. This demonstrates the utility of applying trait-based approaches to microbial community assembly, and the importance of considering changes in community assembly across time.

Increased Production of Pathogenic, Airborne Fungal Spores upon Exposure of a Soil Mycobiota to Chlorinated Aromatic Hydrocarbon Pollutants.

Organic pollutants are omnipresent and can penetrate all environmental niches. We evaluated the hypothesis that short-term (acute) exposure to aromatic hydrocarbon pollutants could increase the potential for fungal virulence. Specifically, we analyzed whether pentachlorophenol and triclosan pollution results in the production of airborne fungal spores with greater virulence than those derived from an unpolluted (Control) condition. Each pollutant altered the composition of the community of airborne spores compared to the control, favoring an increase in strains with in vivo infection capacity (the wax moth Galleria mellonella was used as an infection model). Fungi subsisting inside larvae at 72 h postinjection with airborne spore inocula collected in polluted and unpolluted conditions exhibited comparable diversity (mainly within Aspergillus fumigatus). Several virulent Aspergillus strains were isolated from larvae infected with the airborne spores produced in a polluted environment. Meanwhile, strains isolated from larvae injected with spores from the control, including one A. fumigatus strain, showed no virulence. Potential pathogenicity increased when two Aspergillus virulent strains were assembled, suggesting the existence of synergisms that impact pathogenicity. None of the observed taxonomic or functional traits could separate the virulent from the avirulent strains. Our study emphasizes pollution stress as a possible driver of phenotypic adaptations that increase Aspergillus pathogenicity, as well as the need to better understand the interplay between pollution and fungal virulence. IMPORTANCE Fungi colonizing soil and organic pollutants often meet. The consequences of this encounter constitute an outstanding question. We scrutinized the potential for virulence of airborne fungal spores produced under unpolluted and polluted scenarios. The airborne spores showed increased diversity of strains with higher infection capacity in Galleria mellonella whenever pollution is present. Inside the larvae injected with either airborne spore community, the surviving fungi demonstrated a similar diversity, mainly within Aspergillus fumigatus. However, the isolated Aspergillus strains greatly differ since virulence was only observed for those associated with a polluted environment. The interplay between pollution and fungal virulence still hides many unresolved questions, but the encounter is costly: pollution stress promotes phenotypic adaptations that may increase Aspergillus pathogenicity.

Spore traits mediate disturbance effects on arbuscular mycorrhizal fungal community composition and mutualisms.

Trait-based approaches in ecology are powerful tools for understanding how organisms interact with their environment. These approaches show particular promise in disturbance and community ecology contexts for understanding how disturbances like prescribed fire and bison grazing influence interactions between mutualists like arbuscular mycorrhizal (AM) fungi and their plant hosts. In this work we examined how disturbance effects on AM fungal spore community composition and mutualisms were mediated by selection for specific functional spore traits at both the species and community level. We tested these questions by analyzing AM fungal spore communities and traits from a frequently burned and grazed (bison) tallgrass prairie system and using these spores to inoculate a plant growth response experiment. Selection for darker, pigmented AM fungal spores, changes in the abundance and volume of individual AM fungal taxa, and altered sporulation, were indicators of fire and grazing effects on AM fungal community composition. Disturbance associated changes in AM fungal community composition were then correlated with altered growth responses of Schizachyrium scoparium grass. Our work shows that utilization of trait-based approaches in ecology can clarify the mechanisms that underly belowground responses to disturbance, and provide a useful framework for understanding interactions between organisms and their environment.

Composición de las comunidades de hongos micorrícicos arbusculares en diferentes usos de suelo en el Caldenal, Argentina

Arbuscular mycorrhizal fungi (AMF) are mutualistic symbionts associated with most terrestrial plants. HMA communities vary in composition and life histories and are affected by land use and management. The caldén forests (Prosopis caldenia Burkart) in the province of San Luis have suffered a considerable reduction in their area. Currently, its relics are part of a landscape made up of forests and lands cultivated with Medicago sativa L. (alfalfa) and Eragrostis curvula (Schrad.) Nees (weeping lovegrass), key forage species for livestock production in the region. Considering the ecological and economic importance that these land uses have for the region, the objective of this work was to analyze whether the diversity of AMF is affected by the change in land use from caldén forest to alfalfa or weeping lovegrass plots and whether there are indicator species for each use. Four plots of permanent forest were established, 4 of alfalfa and 4 of weeping lovegrass. Soil samples were taken from each plot, the physicochemical characteristics were determined and the AMF spores were extracted. The composition of the spore communities was different in each land use. The AMF morphospecies richness did not showed differences between forest and alfalfa but show differences with weeping lovegrass. Total abundance, spore abundance of ruderal and stress-tolerant species were significantly higher in alfalfa. In addition, 2 indicator species were identified in alfalfa, 1 in forests, and 2 in weeping love grass. This study provides evidence suggesting that land-use change in Caldenal significantly alters the composition of AMF spore communities and may have a negative effect on this endemic forest.

Environmental response of arbuscular mycorrhizal fungi under soybean cultivation at a regional scale.

Climate change, the shortage of fertilizers and reduced land for cultivation have drawn attention to the potential aid provided by soil-borne organisms. Arbuscular mycorrhizal fungi (AMF) offer a wide range of ecosystem benefits and hence, understanding the mechanisms that control AMF occurrence and maintenance is essential for resilient crop production. We conducted a survey of 123 soybean fields located across a 75,000-km2 area of Argentina to explore AMF community composition and to quantify the impact of soil, climate, and geographical distance on these key soil organisms. First, based upon morphological identification of spores, we compiled a list of the AMF species found in the studied area and identified Acaulospora scrobiculata and Glomus fuegianum as the most frequent species. G. fuegianum abundance was negatively correlated with precipitation seasonality and positively correlated with mean annual precipitation as well as mycorrhizal colonisation of soybean roots. Second, we observed that species richness was negatively correlated with soil P availability (Bray I), clay content and mean annual precipitation. Finally, based on partitioning variation analysis, we found that AMF exhibited spatial patterning at a broad scale. Therefore, we infer that geographical distance was positively associated with spore community composition heterogeneity across the region. Nevertheless, we highlight the importance of precipitation sensitivity of frequent species, overall AMF richness and community composition, revealing a crucial challenge to forthcoming agriculture considering an expected change in global climate patterns.

Composition and seasonal variation of the arbuscular mycorrhizal fungi spore community in litter, root mat, and soil from a subtropical rain forest

Community composition and seasonal variation of sporulation of arbuscular mycorrhizal fungi (AMF) have been studied in soils from many ecosystems including subtropical forest. Yet, AMF community composition has been surveyed only from the mineral soil but not from the litter layer and the root mat, and long-term variation in sporulation is not fully understood. We sampled a 75-m2 plot from a subtropical forest to determine AMF community composition in the following habitats: the litter layer, the root mat, and the mineral soil. Moreover, samples were taken in fall, winter, spring, and summer over a 2-year period to follow the seasonal variation of AMF sporulation. We detected 47 AMF species belonging to six families and 14 genera, Glomeraceae and Acaulosporaceae being the most represented families. Sixteen species were common to all three habitats, five species were shared between two habitats, and 26 species were recovered exclusively from single habitats. While species richness was not significantly different among habitats, AMF total spore numbers were significantly higher in the litter and root mat compared to the soil. PERMANOVA did not detect a significant effect of habitats on community composition when species presence/absence was considered, but significant differences between litter versus soil and root mat versus soil were detected when spore abundance was considered. A seasonal pattern of spore abundance for species was not observed over the 2-year sampling period regardless of habitat. This study revealed that (i) different AMF species sporulate in the different habitats; thus, field surveys considering only the mineral soil might underestimate species richness and (ii) AMF species sporulate asynchronously in subtropical forest.

Host genotype interacts with aerial spore communities and influences the needle mycobiome of Norway spruce.

SummaryThe factors shaping the composition of the tree mycobiome are still under investigation. We tested the effects of host genotype, site, host phenotypic traits, and air fungal spore communities on the assembly of the fungi inhabiting Norway spruce needles. We used Norway spruce clones and spore traps within the collection sites and characterized both needle and air mycobiome communities by high‐throughput sequencing of the ITS2 region. The composition of the needle mycobiome differed between Norway spruce clones, and clones with high genetic similarity had a more similar mycobiome. The needle mycobiome also varied across sites and was associated with the composition of the local air mycobiome and climate. Phenotypic traits such as diameter at breast height or crown health influenced the needle mycobiome to a lesser extent than host genotype and air mycobiome. Altogether, our results suggest that the needle mycobiome is mainly driven by the host genotype in combination with the composition of the local air spore communities. Our work highlights the role of host intraspecific variation in shaping the mycobiome of trees and provides new insights on the ecological processes structuring fungal communities inhabiting woody plants.

Hurricane María drives increased indoor proliferation of filamentous fungi in San Juan, Puerto Rico: a two-year culture-based approach.

Extensive flooding caused by Hurricane María in Puerto Rico (PR) created favorable conditions for indoor growth of filamentous fungi. These conditions represent a public health concern as contamination by environmental fungi is associated with a higher prevalence of inflammatory respiratory conditions. This work compares culturable fungal spore communities present in homes that sustained water damage after Hurricane María to those present in dry, non-flooded homes. We collected air samples from 50 houses in a neighborhood in San Juan, PR, 12 and 22 months after Hurricane María. Self-reported data was used to classify the homes as flooded, water-damage or dry non-flooded. Fungi abundances, composition and diversity were analyzed by culturing on two media. Our results showed no significant differences in indoor fungal concentrations (CFU/m3) one year after the Hurricane in both culture media studied (MEA and G25N). During the second sampling period fungal levels were 2.7 times higher in previously flooded homes (Median = 758) when compared to dry homes (Median = 283), (p-value < 0.005). Fungal profiles showed enrichment of Aspergillus species inside flooded homes compared to outdoor samples during the first sampling period (FDR-adjusted p-value = 0.05). In contrast, 22 months after the storm, indoor fungal composition consisted primarily of non-sporulated fungi, most likely basidiospores, which are characteristic of the outdoor air in PR. Together, this data highlights that homes that suffered water damage not only have higher indoor proliferation of filamentous fungi, but their indoor fungal populations change over time following the Hurricane. Ultimately, after nearly two years, indoor and outdoor fungal communities converged in this sample of naturally ventilated homes.

Wildfire does not affect spore abundance, species richness, and inoculum potential of arbuscular mycorrhizal fungi (Glomeromycota) in ferruginous Canga ecosystems

Canga ecosystems develop over superficial iron crusts with shallow and nutrient-poor soils. Under these conditions, arbuscular mycorrhizal fungi (AMF) play an important role in helping plants to overcome abiotic and biotic stresses. Canga can suffer periodic burning and yet it is unknown what the impacts of fire are to AMF communities. We aimed to compare AMF in Canga areas affected by burning (BC) with those with no previous history of burning (NC). We compared AMF species composition, spore numbers, species richness, and mycorrhizal inoculum potential. The total number of spores, AMF species richness and mycorrhizal colonization measured in the infectivity bioassay were not significantly different between areas. A total of 23 species in 10 genera were recovered, with most species belonging to Gigasporaceae and Acaulosporaceae. BC and NC shared 52 % of AMF species. Gigaspora albida, Gigaspora gigantea, and Dentiscutata heterogama sporulated exclusively in trap cultures. We concluded that AMF spore communities were not affected by burning in Canga soils as measured by spore abundance, species richness and infectivity. Our data contribute to the inventory of soil biodiversity associated with Canga, a high biodiverse and threatened Brazilian ecosystem.

Soybean growth and foliar phosphorus concentration mediated by arbuscular mycorrhizal fungi from soils under different no-till cropping systems

Soil use and management modify mycorrhizal interactions, but how these changes affect the growth and nutrition of crops under different contexts has been poorly studied. The objective of this study was to evaluate the effects of arbuscular mycorrhizal fungal (AMF) spore communities belonging to two no-till cropping systems (soybean monoculture and soybean-maize rotation), and uncultivated grasslands replicated at four locations along a regional geographic gradient on soybean mycorrhizal colonization and performance. At a regional scale, AMF spore richness was higher in uncultivated grasslands, intermediate in crop rotations, and lower in monocultures. Arbuscular mycorrhizal colonization in soybean roots was also higher in uncultivated soils but did not differ between no-tillage systems. Soybean growth was positively affected by AMF from uncultivated grasslands in comparison to control without AMF. Instead, there were no significant effects of AMF from no-till cropping systems. Foliar P concentration was lower in monocultures irrespective of AMF. At the local scale, patterns were highly variable and differed between locations. These results highlight the importance of scales for management decisions in agriculture and add further support for the context-dependent nature of mycorrhizal interactions.

El "siempreverde" (Ligustrum lucidum), ¿Altera la composición de las comunidades de hongos micorrícicos arbusculares en el Chaco Serrano?

Biological invasions represent a major threat to biodiversity and the integrity of ecosystems, since they generate alterations in biotic communities. Among the biotic soil communities, arbuscular mycorrhizal fungi (AMF) are a major component establishing symbiotic associations with the majority of land plants. The HMA species do not respond in the same way to environmental changes; so, the existence of groups of HMA species with shared ecological strategies (ruderals, competitors and stress-tolerants) was proposed. Invasive plants are capable of altering AMF communities for their own benefit. This could be the case of the “glossy privet” (Ligustrum lucidum), an Asian tree that invades important areas of Argentina and forms dense monospecific stands in certain locations. In this study, the HMA spore communities were compared between glossy privet monospecific forests and native Chaco Serrano forests. Six areas were selected with both types of forest. We obtained soil samples from which AMF spores were extracted and physicochemical properties were measured. As expected, the spore community composition differed between monospecific glossy privet stands and native forests. The HMA spore richness did not differ between both types of forest but the total abundance was higher in glossy privet stands that show a higher spore abundance of ruderal AMF species. This study provides evidence that suggests that L. lucidum expansion alters certain soil chemical properties and HMA spore communities. These changes may feedback on glossy privet growth and promote the formation of monospecific stands.

Soil legacy determines arbuscular mycorrhizal spore bank and plant performance in the low Arctic

Human impact is rapidly changing vegetation globally. The effect of plant cover that no longer exists in a site may still affect the development of future vegetation. We focused on a little studied factor—arbuscular mycorrhizal (AM) fungus spore bank—and its effect on three test plant species. In a low Arctic field site, plots were maintained for 6 years, devoid of any vegetation or with a Solidago virgaurea monoculture cover. We analysed the AM fungal morphospecies composition and identified 21 morphospecies in the field plots. The AM morphospecies community was dominated by members of Acaulosporaceae. Monoculturing under low Arctic field conditions changed the soil AM spore community, which became dominated by Glomus hoi. We tested the soil feedback in the greenhouse and grew Solidago virgaurea, Potentilla crantzii and Anthoxanthum odoratum in the field soils from the plots without plant cover, covered with Solidago virgaurea or with intact vegetation. Our results suggest that monoculturing resulted in improved N acquisition by the monocultured plant species Solidago virgaurea which may be related to the AM fungus community. Our results show that a rich community of AM fungus spores may remain viable under field conditions for 6 years in the low Arctic. Spore longevity in field soil in the absence of any host plants differed among AM fungus species. We suggest that AM fungus spore longevity be considered an AM fungal life-history trait.

Vegetation type determines spore deposition within a forest-agricultural mosaic landscape.

ABSTRACTPredicting fungal community assembly is partly limited by our understanding of the factors driving the composition of deposited spores. We studied the relative contribution of vegetation, geographical distance, seasonality and weather to fungal spore deposition across three vegetation types. Active and passive spore traps were established in agricultural fields, deciduous forests and coniferous forests across a geographic gradient of ∼600 km. Active traps captured the spore community suspended in air, reflecting the potential deposition, whereas passive traps reflected realized deposition. Fungal species were identified by metabarcoding of the ITS2 region. The composition of spore communities captured by passive traps differed more between vegetation types than across regions separated by >100 km, indicating that vegetation type was the strongest driver of composition of deposited spores. By contrast, vegetation contributed less to potential deposition, which followed a seasonal pattern. Within the same site, the spore communities captured by active traps differed from those captured by passive traps. Realized deposition tended to be dominated by spores of species related to vegetation. Temperature was negatively correlated with the fungal species richness of both potential and realized deposition. Our results indicate that vegetation may be able to maintain similar fungal communities across distances, and likely be the driving factor of fungal spore deposition at landscape level.

The underappreciated role of rodent generalists in fungal spore dispersal networks.

Animals are often the primary dispersers of seeds and fungal spores. Specialist species that consume fruits or fungal fruiting bodies (sporocarps) as their main food source are thought to play a more important role in dispersal networks compared to generalist species. However, dispersal networks are often based on occurrence data, overlooking the influence of animal abundance and dispersal effectiveness on network interactions. Using rodent-mycorrhizal fungi networks, we determined how diet specialization and abundance influence the role of rodent species in dispersing fungal spores in temperate forests of northern New Hampshire, USA. We tracked the interactions of five rodent species and 34 fungal taxa over a 3-yr period across hardwood, mixed, and softwood forest stands. We accounted for fluctuations in rodent abundance and differences in the number of spores dispersed in rodent scat. Myodes gapperi, a fungal specialist, dispersed a more diverse spore community than rodent generalists and was consistently the most important disperser in forest types with high fungal availability. Nevertheless, during years when generalist species such as Tamias striatus and Peromyscus maniculatus reached high abundance, their relative importance (species strength) in networks approached or even surpassed that of M. gapperi, particularly in forest types where M. gapperi was less common and fungal availability was low. Increased numbers of generalists enhanced network interaction diversity and the number of fungal taxa dispersed, the timing of which was coincident with seedling establishment following masting, a stage when inoculation by mycorrhizal fungi is critical for growth and survival. Our findings suggest that although specialists play key roles in dispersing mycorrhizal fungal spores, generalists play a heretofore underappreciated role.

Arbuscular Mycorrhizal and Dark Septate Endophyte Fungal Association in Cassava (Manihot esculenta Crantz) Varieties, Southern India

The study examined the root characteristics, type of arbuscular mycorrhizal (AM) and dark septate endophyte (DSE) fungal associations and their extent of colonization in 13 widely cultivated cassava (Manihot esculenta Crantz) varieties in southern India. Root and associated soil samples of each cassava variety were collected from Salem and Kolli Hills of the Eastern Ghats in south India. In addition, we also investigated the relationship between the extent of colonization of AM, DSE fungal and AM fungal spore communities and soil characteristics for each cassava variety. Roots of all the cassava varieties were colonized by AM fungi and 12 varieties had co-colonization of DSE fungi. The AM morphology in all the cassava varieties was of an intermediate type with intercellular and intracellular linear hyphae and arbusculate coils. In addition, we found high AM colonization rates (73-89%) but only moderate rates by DSE (22-68%) fungi. We also found 17 AM fungal spore morphotypes and their abundance varied significantly among cassava varieties. In addition, different physicochemical properties of soils may possibly increase AMF diversity, while different varieties of cassava are commonly associated with differing levels of AM and DSE fungi colonization with soil factors potentially influencing the symbiosis.

Arbuscular mycorrhizal fungal communities in soils under three phytophysiognomies of the Brazilian Atlantic Forest

ABSTRACT Arbuscular mycorrhizal fungi (AMF) play an important role in plant community productivity and structure, and so studying the factors that affect the diversity and structure of this fungal community is important for understanding their ecology in tropical forests. We investigated AMF spore communities and root colonization under three forest phytophysiognomies (Restinga Forest, REF; Lowland Ombrophilous Dense Forest, LLF; and Montane Ombrophilous Dense Forest, MTF). Spore abundance was lowest in LLF and highest in REF, with no statistical differences relative to MTF. Spore diversity indices and root colonization rates were not statistically different among the phytophysiognomies. However, principal components analysis revealed that AMF community structure differed according to forest phytophysiognomy. Hierarchical partitioning analysis indicated that most of the AMF community variables were better explained by phytophysiognomy than by chemical and physical attributes of the soil. In addition to the plant community, clay content, pH, Boron, P, S and CEC best explained some of the AMF community variables. Thus, we conclude that while several factors determine AMF community structure in the Atlantic Forest, phytophysiognomy is the most significant.

Soil constraints for arbuscular mycorrhizal fungi spore community in degraded sites of rupestrian grassland: Implications for restoration

The arbuscular mycorrhizal fungi (AMF) are important organisms with enormous potential for use in ecological restoration due to their positive association to seedlings. We evaluated the effects of soil degradation on a species-rich AMF community that could hinder the restoration of rupestrian grassland sites whose soil had been removed. Soil samples were taken from reference and degraded sites. We assessed the density, species richness, and composition of AMF, as well as soil macronutrients, metals, and texture. We found lower AMF density and richness in degraded than in reference sites. AMF community seemed to be negatively affected by a low level of potassium (K) and a higher concentration of heavy metals and clay in degraded sites. Besides the shifts in AMF composition associated mainly with K concentration, we found that the lack of this nutrient in degraded sites was also related to a significant reduction in density of AMF species, which are thought to play important roles in plant development and, therefore, in ecological restoration. Thus, we emphasize that efforts to restore degraded areas of rupestrian grassland should contemplate the reestablishment of soil physical and chemical properties, such as a lower clay concentration, and levels of nutrients that are key for AMF colonization. In addition, we suggest the further development of protocols for inoculation of seedlings and soil with AMF species to improve the success of replantation.

Differential responses to high soil chromium of two arbuscular mycorrhizal fungi communities isolated from Cr-polluted and non-polluted rhizospheres of Ricinus communis

Arbuscular mycorrhizal fungi (AMF) are symbionts in roots of 70–90% of terrestrial plants, and are present even in highly perturbed sites like soils polluted with potentially toxic elements (PTE). Plants and indigenous AMF present in polluted soils may play an important role in PTE uptake (phytoextraction) and complexation (phytostabilization). The present work was addressed to: i) analyze the spore community structure of AMF associated to Ricinus communis rhizospheres from a chromium (Cr) polluted site (MOR) and a non-Cr polluted site (PAR); ii) analyze whether plant growth and mycorrhizal colonization of R. communis, and Cr(VI) remaining concentration in soil, differed in both rhizosphere soils when exposed to a mixture of Cr(III)/Cr(VI) polluting concentration in a greenhouse experiment. Culture trap from both rhizosphere soil were established previously to the study to propagate AMF. The community structure was analyzed with morphological and molecular approaches. The spore community structure differed in MOR as related to PAR rhizosphere soils: Acaulosporaceae and Gigasporaceae morphotypes were only observed in PAR and Paraglomeraceae ribotypes were detected only in MOR. Finally, a greenhouse experiment was designed to study the response of both communities when grown in association with R. communis and exposed to polluting concentrations of Cr(III)/Cr(VI) (250/8μgg−1 soil d.w.). The mycorrhizal colonization was higher in roots grown in presence of MOR than in presence of PAR AMF community, exposed or not to Cr, and the final Cr(VI) concentration in soil was lower in the pots with MOR AMF community than in the pots with PAR AMF community (6.9±0.2 and 14.3±1.5μgCr(VI)g−1 soil d.w., respectively). Our results suggest that the previous exposure to polluting concentration of Cr could have selected AMF species with a higher infectivity and thus more likely to better contribute to reduce the pollutant concentration in the soil.

Arbuscular mycorrhizal fungal spore communities of a tropical dry forest ecosystem show resilience to land-use change

Abstract We explored the resilience of arbuscular mycorrhizal fungal (AMF) communities of a tropical dry forest ecosystem to land use as pastures. We compared spore community species richness, composition, abundance, and similarity between old-growth forests and active pastures, as a measure of resistance and examined the trajectory of change in successional fields when pasture use stopped to evaluate recovery. Despite a few changes in species richness, community composition and structure were strikingly similar in all sites, including the active pastures. The spore communities were considered resistant to land use as pastures and showed minor changes along succession when management stopped. We found a significant negative relation between the frequency of Diversisporales and Glomerales indicating a selective species turnover driven mainly by the families Gigasporaceae and Glomeraceae. This was, however, unrelated to land use or successional time. These results suggest the AMF communities of this ecosystem seem resilient to management as pastures.