Monotropa uniflora plants of eastern Massachusetts form mycorrhizae with a diversity of russulacean fungi

Plant species in the subfamily Monotropoideae are mycoheterotrophs; they obtain fixed carbon from photosynthetic plants via a shared mycorrhizal network. Previous findings show mycoheterotrophic plants exhibit a high level of specificity to their mycorrhizal fungi. In this study we explore the association of mycorrhizal fungi and Monotropa uniflora (Monotropoideae: Ericaceae) in eastern North America. We collected M. uniflora roots and nearby basidiomycete sporocarps from four sites within a 100 km2 area in eastern Massachusetts. We analyzed DNA sequences of the internal transcribed spacer region (ITS) from the fungal nuclear ribosomal gene to assess the genetic diversity of fungi associating with M. uniflora roots. In this analysis we included 20 ITS sequences from Russula sporocarps collected nearby, 44 sequences of Russula or Lactarius species from GenBank and 12 GenBank sequences of fungi isolated from M. uniflora roots in previous studies. We found that all 56 sampled M. uniflora mycorrhizal fungi were members of the Russulaceae, confirming previous research. The analysis showed that most of the diversity of mycorrhizal fungi spreads across the genus Russula. ITS sequences of the mycorrhizal fungi consisted of 20 different phylotypes: 18 of the genus Russula and two of Lactarius, based on GenBank searches. Of the sampled plants, 57% associated with only three of the 20 mycorrhizal fungi detected in roots, and of the 25 sporocarp phylotypes collected three, were associated with M. uniflora. Furthermore the results indicate that the number of different fungal phylotypes associating with M. uniflora of eastern North America is higher than that of western North America but patterns of fungal species abundance might be similar between mycorrhizae from the two locations.     

Mycorrhizal fungi associated with Monotropastrum humile (Ericaceae) in central Japan

We explored the diversity of mycorrhizal fungi associated with Monotropastrum humile in the central part of Japan's main island. We collected 103 M. humile individuals from 12 sites with various forest types. We analyzed the DNA sequences of the internal transcribed spacer region from fungal and plant nuclear ribosomal DNAs to assess the genetic diversity of the fungi associated with M. humile roots and to position the plant with respect to known Monotropoideae groups, respectively. The plants formed a monophyletic clade with other members of M. humile but were separated from M. humile var. glaberrimum and other monotropes (97% bootstrap support). Of the 50 fungal phylotypes, 49 had best matches with the Russulales, and the other had highest similarity with the Thelephoraceae. Our phylogenetic analysis suggests that M. humile roots have a highly specialized association with fungal partners in the Russulaceae. Moreover, a few fungal phylotypes from the M. humile roots had positions neighboring those from Monotropa uniflora roots. These results indicated that the genetic diversity of mycorrhizal fungi of M. humile was highly specific to the Russulaceae, but with high diversity within that family, and that the fungi associated with M. humile differ from those associated with M. uniflora.     

Arbuscular mycorrhiza (AM) status of rehabilitation plants of mine wastes in South Africa and determination of AM fungal diversity by analysis of the small subunit rRNA gene sequences

The aim of this study was to assess the arbuscular mycorrhizal (AM) status of trees currently being used for phytoremediation of mining contaminated sites in South Africa, and to determine the AM fungal diversity of these sites. The trees, Tamarix usneoides, Searsia lancea and Searsia pendulina planted on waste sites associated with gold and uranium and zinc and platinum mining were assessed in late summer and the AM fungi were identified by molecular analysis of the small subunit rRNA gene sequences from spore DNA. All trees on all sites showed moderate to high mycorrhizal colonisation levels including those from wild populations of T. usneoides growing in uncontaminated sites. The AM fungi identified fell within the Claroideoglomus, Diversispora, Glomus, Acaulospora and Sclerocystis taxa and although their species diversity was relatively low there were distinct trends in their association with the three plant species sampled. The study represents a first report of the mycorrhizal status of T. usneoides and of the use of molecular techniques for the identification of AM fungi associated with mine wastes in South Africa. The results will assist in making decisions about the application of AM fungal inoculum in phytoremediation programmes for mine waste rehabilitation.     

Diversity of culturable ericoid mycorrhizal fungi of Rhododendron decorum in Yunnan, China

The diversity of ericoid mycorrhizal fungi isolated from Rhododendron decorum Franch. in Yunnan, southwestern China, was examined for the first time. In total 300 hair-root samples were collected from 13 R. decorum individuals in two adjacent wild population sites and one cultivated population site. Two hundred eighteen slow-growing isolates were obtained; the ability of some to form ericoid mycorrhiza was tested in vitro. One hundred twenty-five isolates formed hyphal structures morphologically corresponding to ericoid mycorrhiza, and these were determined by morphological and molecular means to belong to 12 fungal species. There were hardly any differences in species among the three sampled populations. The sequences of several isolates were similar to those of Oidiodendron maius and ericoid mycorrhizal fungi from Helotiales, accounting respectively for 18.4% and 24.8% of the total culturable ericoid mycorrhizal fungi assemblage. Dark septate endophytes were detected in the sampled hair roots by microscopy.     

Evidence for mycorrhizal races in a cheating orchid

Disruptive selection on habitat or host-specificity has contributed to the diversification of several animal groups, especially plant-feeding insects. Photosynthetic plants typically associate with a broad range of mycorrhizal fungi, while non-photosynthetic plants that capture energy from mycorrhizal fungi ('mycoheterotrophs') are often specialized towards particular taxa. Sister myco-heterotroph species are often specialized towards different fungal taxa, suggesting rapid evolutionary shifts in specificity. Within-species variation in specificity has not been explored. Here, we tested whether genetic variation for mycorrhizal specificity occurs within the myco-heterotrophic orchid Corallorhiza maculata. Variation across three single-nucleotide polymorphisms revealed six multilocus genotypes across 122 orchids from 30 sites. These orchids were associated with 22 different fungal species distributed across the Russulaceae (ectomycorrhizal basidiomycetes) according to internal-transcribed-spacer sequence analysis. The fungi associated with four out of the six orchid genotypes fell predominantly within distinct subclades of the Russulaceae. This result was supported by Monte Carlo simulation and analyses of molecular variance of fungal sequence diversity. Different orchid genotypes were often found growing in close proximity, but maintained their distinct fungal associations. Similar patterns are characteristic of insect populations diversifying onto multiple hosts. We suggest that diversification and specialization of mycorrhizal associations have contributed to the rapid radiation of the Orchidaceae.     

Population, habitat and genetic correlates of mycorrhizal specialization in the 'cheating' orchids corallorhiza maculata and C. mertensiana

Unlike photosynthetic plants, several distantly related nonphotosynthetic plants are highly specialized toward their mycorrhizal fungi. It is unknown whether this specialization varies geographically or is influenced by the environment. We have investigated these questions in the nonphotosynthetic orchids Corallorhiza maculata and C. mertensiana by amplifying fungal internal transcribed spacer (ITS) fragments from widespread mycorrhiza samples and then discriminating putative fungal species using ITS restriction fragment length polymorphisms (RFLPs). Three fungal species were found across 27 plants representing seven populations of C. mertensiana; 20 species were found across 104 plants and 21 populations of C. maculata. All fungi belonged to the Russulaceae, an ectomycorrhizal family. Partitioning of Simpson's diversity showed that 48% of the variance in occurrences of fungal species coincided with population boundaries in C. mertensiana, vs. 68% in C. maculata. This differentiation coincided with geography but not habitat in C. mertensiana. In contrast, likelihood ratio tests showed strong associations between fungal occurrence and both habitat and phenotype in C. maculata. For example, C. maculata populations growing under oaks had no fungi in common with nearby populations growing under conifers, and those above 2000 m had no fungi in common with those below 2000 m. However, plant genetic differentiation may underlie some of these patterns. C. mertensiana and C. maculata never shared fungal species, even when growing intermixed at the same site, demonstrating genetic control that was independent of habitat. Similarly, intermixed normal and pale-coloured variants of C. maculata had no fungal species in common. These results demonstrate fine-scale genetic influences and geographical mosaicism in a mycorrhizal interaction.     

Influence of host species on ectomycorrhizal communities associated with two co-occurring oaks (Quercus spp.) in a tropical cloud forest

Interactions between host tree species and ectomycorrhizal fungi are important in structuring ectomycorrhizal communities, but there are only a few studies on host influence of congeneric trees. We investigated ectomycorrhizal community assemblages on roots of deciduous Quercus crassifolia and evergreen Quercus laurina in a tropical montane cloud forest, one of the most endangered tropical forest ecosystems. Ectomycorrhizal fungi were identified by sequencing internal transcribed spacer and partial 28S rRNA gene. We sampled 80 soil cores and documented high ectomycorrhizal diversity with a total of 154 taxa. Canonical correspondence analysis indicated that oak host was significant in explaining some of the variation in ectomycorrhizal communities, despite the fact that the two Quercus species belong to the same red oak lineage (section Lobatae ). A Tuber species, found in 23% of the soil cores, was the most frequent taxon. Similar to oak-dominated ectomycorrhizal communities in temperate forests, Thelephoraceae, Russulaceae and Sebacinales were diverse and dominant.     

Diversity and structure of ectomycorrhizal and co-associated fungal communities in a serpentine soil

The community of ectomycorrhizal (ECM) and co-associated fungi from a serpentine site forested with Pinus sylvestris and Quercus petraea was explored, to improve the understanding of ECM diversity in naturally metalliferous soils. ECM fungi were identified by a combination of morphotyping and direct sequencing of the nuclear ribosomal internal transcribed spacer region 2 and of a part of the large-subunit region. Co-associated fungi from selected ECM were identified by restriction fragment length polymorphism and sequencing of representative clones from libraries. Polymerase chain reaction with species-specific primers was applied to assess patterns of association of ECM and co-associated fungi. Twenty ECM species were differentiated. Aphyllophoralean fungi representing several basidiomycete orders and Russulaceae were dominant. Phialocephala fortinii was the most frequently encountered taxon from the diverse assemblage of ECM co-associated fungi. A ribotype representing a deeply branching ascomycete lineage known from ribosomal deoxyribonucleic acid sequences only was detected in some ECM samples. A broad taxonomic range of fungi have the potential to successfully colonise tree roots under the extreme edaphic conditions of serpentine soils. Distribution patterns of ECM-co-associated fungi hint at the importance of specific inter-fungal interactions, which are hypothesised to be a relevant factor for the maintenance of ECM diversity.     

The diversity of mycorrhizal fungi in Japanese Cephalanthera species

The diversity of mycorrhizal fungi among four Japanese Cephalanthera (Orchidaceae) species was examined at a total of seven sites, based on sequence variation in nuclear ribosomal DNA. This is the first report to detect mycorrhizal fungi in C. subaphylla. Two patterns of mycorrhizal associations were confirmed from our results. C. falcata has lower fungal specificity, associating with Russulaceae, Sebacinales and Thelephoraceae. By contrast, the three Cephalanthera species C. erecta, C. subaphylla, and C. longifolia were associated mainly with Thelephoraceae fungi. There is no large difference found in mycobionts between green and albino individuals of C. falcata and no distinct preference of Japanese Cephalanthera species for a specific fungal group of Thelephoraceae.     

Fungal relationships and structural identity of their ectomycorrhizae

Aproximately 5,000–6,000 fungal species form ectomyorrhizae (ECM), the symbiotic organs with roots of predominantly trees. The contributing fungi are not evenly distributed over the system of fungi. Within Basidiomycota exclusively Hymenomycetes and within Ascomycota exclusively Ascomycetes contribute to the symbiosis. Hymenomycetes play a big part, Ascomycetes a minor role; Zygomycetes only form exceptionally ECM. Responsible for ascomycetous ECM are mostly Pezizales with their hypogeous derivatives, whereas Boletales, Gomphales, Thelephorales, Amanitaceae, Cantharellaceae, Cortinariaceae, Russulaceae, and Tricholomataceae are the most important ectomycorrhizal relationships within Hymenomycetes. ECM, as transmitting organs between soil and roots, are transporting carbohydrates for growth of mycelium and fruitbodies from roots and have to satisfy the tree’s demand for water and nutrients. The latter task particularly influences the structure of ECM as nutrients are patchily distributed in the soil and saprotrophic as well as ectomycorrhizal fungi can act as strong competitors for nutrients. In focusing these requirements, ECM developed variously structured hyphal sheaths around the roots, the so-called mantles, and differently organized mycelium that emanates from the mantle, the so-called extramatrical mycelium. The mantles can be plectenchymatous consisting of loosely woven, differently arranged hyphae or they are densely packed, forming a pseudoparenchyma similar to the epidermis of leaves. The extramatrical mycelium grows either as simple scattered hyphae from the mantle into the soil or it can be united to undifferentiated rhizomorphs with a small reach or to highly organized root-like organs with vessel-like hyphae for efficient water and nutrient transport from distances of decimeters. Cystidia, sterile and variously shaped hyphal ends, possibly appropriate for preventing animal attack, in addition, can cover mantles and rhizomorphs. Although only a limited number of species could be considered, some general conclusions are possible.The genus Tuber forms needle-shaped cystidia and lacks rhizomorphs and clamps. Gomphales ECM are identified by rhizomorphs with ampullate inflations at septa of some hyphae and by oleoacanthocystidia or/and oleoacanthohyphae. Thelephoraceae reveal a great diversity of mantle structures and of extramatrical mycelium, with some additional optional characters, i.e., dark brown color, cystidia, blue granules, amyloid hyphae, or amyloid septa. Bankeraceae are mostly characterized by plectenchymatous mantles with star-like pattern and chlamydospores. Russulaceae possess smooth and hydrophilic ECM. Russula forms plectenchymatous mantles with knob-bearing cystidia, so-called russuloid cystidia, or pseudoparenchymatous mantles without cystidia. Lactarius lacks cystidia and shows laticifers within plectenchymatous or within pseudoparenchymatous mantles. The Boletales families Boletaceae, Gyroporaceae, Melanogastraceae, Paxillaceae, Rhizopogonaceae, Sclerodermataceae, and Suillaceae have the most advanced rhizomorph type, the so-called boletoid rhizomorphs, and reveal generally plectenchymatous mantles, frequently with ring-like patterns. Gomphidiaceae and Albatrellaceae provide cystidia, plectenchymatous mantles, and amyloidy; Gomphidiaceae are generally growing in ECM of Suillaceae and Rhizopogonaceae. Cortinariaceae reveal plectenchymatous mantles and undifferentiated or differentiated rhizomorphs or lack rhizomorphs at all. Cortinarius and Dermocybe are distinct by irregularly shaped, bent to tortuous ECM with many rhizomorphs, some growing over the mycorrhizal tip into the soil. Inocybe lacks rhizomorphs and its emanating hyphae are furnished by many secondary septa and prominent clamps with a hole. Rozites lacks rhizomorphs, too, and reveals a distinctly amyloid gelatinous mantle matrix. Descolea and Descomyces are covered by bolbitioid cystidia. Lastly, the genus Tricholoma forms plectenchymatous mantles and a high diversity of rhizomorphs. Some of the ectomycorrhizal features are used to hypothesize relationships at different taxonomic levels. These conclusions are compared with recently developed molecular hypotheses. Correspondence between the two types of hypotheses are evident, while some conflicts wait for a settlement.     

Mycorrhizas in the Kakadu region of tropical Australia

This research represents the first part of a study which aimed to characterize the role of mycorrhizal associations in undisturbed and disturbed habitats in the Alligator Rivers Region of the Northern Territory of Australia. This is a seasonally dry tropical region with a climate consisting of a long dry season and a monsoonal wet season. Intact soil cores were sampled from 22 sites in this region, representing eucalypt savanna woodland, wetland, rocky hill and rainforest habitats. Clover, sorghum and eucalypt seedlings were grown in these cores in bioassays to measure the inoculum potential of vesicular-arbuscular mycorrhizal (VAM) and ectomycorrhizal (ECM) fungi. Propagules of VAM fungi were concentrated in the surface horizon, and were not adversely affected by 6 months dry storage of soil. Bioassays detected VAM fungus propagules at all sites, but these were less numerous in three sites with sparse herbaceous vegetation (a shrub-dominated woodland site, a sandstone area and a disturbed gravel pit without topsoil), than in other woodland sites. Propagules of VAM fungi were particularly numerous in soil from a rainforest habitat, which had much denser plant cover than any of the savanna sites. Propagules of ECM fungi colonized eucalypt seedling roots in some cores from all sites, except two wetland areas and a disturbed area without eucalypt trees. Physical and chemical properties of soils varied between sites and some properties (texture, organic carbon, etc.) were correlated with the inoculum potential of VAM fungi.     

Biological invasions increase the richness of arbuscular mycorrhizal fungi from a Hawaiian subtropical ecosystem

Biological invasions can have various impacts on the diversity of important microbial mutualists such as mycorrhizal fungi, but few studies have tested whether the effects of invasions on mycorrhizal diversity are consistent across spatial gradients. Furthermore, few of these studies have taken place in tropical ecosystems that experience an inordinate rate of invasions into native habitats. Here, we examined the effects of plant invasions dominated by non-native tree species on the diversity of arbuscular mycorrhizal (AM) fungi in Hawaii. To test the hypothesis that invasions result in consistent changes in AM fungal diversity across spatial gradients relative to native forest habitats, we sampled soil in paired native and invaded sites from three watersheds and used amplicon sequencing to characterize AM fungal communities. Whether our analyses considered phylogenetic relatedness or not, we found that invasions consistently increased the richness of AM fungi. However, AM fungal species composition was not related to invasion status of the vegetation nor local environment, but stratified by watershed. Our results suggest that while invasions can lead to an overall increase in the diversity of microbial mutualists, the effects of plant host identity or geographic structuring potentially outweigh those of invasive species in determining the community membership of AM fungi. Thus, host specificity and spatial factors such as dispersal need to be taken into consideration when examining the effects of biological invasions on symbiotic microbes.     

Relationships between soil heavy metal concentration and mycorrhizal colonisation in<Emphasis Type="Italic"> Thymus polytrichus</Emphasis> in northern England

A study was conducted to establish whether the wild thyme [Thymus polytrichus A. Kerner ex Borbás ssp. britannicus (Ronn.) Kerguelen (Lamiaceae)] growing in the metal-contaminated soils along the River South Tyne, United Kingdom, is colonised by arbuscular mycorrhizal (AM) fungi, and whether the degree of colonisation increases (perhaps suggesting increasing mycorrhizal dependence) or decreases (indicating possible inhibition of AM growth) with increasing degree of soil contamination. Seasonal changes in AM colonisation were also assessed. The AM fungal communities colonising T. polytrichus were also investigated, using the polymerase chain reaction with restriction fragment length polymorphism and sequencing of fungal DNA to establish whether AM species richness varied between sites, and whether fungal ecotypes specific to sites with different amounts of metal contamination could be identified. All plants examined were heavily colonised by AM fungi, and mean percentage root length colonised did not increase significantly with increasing soil metal contamination. However, AM vesicle abundance (percentage of mycorrhizal root length containing vesicles) at the most contaminated site was significantly greater than at the other sites. No significant seasonal variation in degree of colonisation or vesicle abundance was found. Glomus was the predominant AM genus detected at all sites. The number of AM genotypes colonising T. polytrichus roots was similar at all sites but, although some were common to all sites, certain strains appeared to be specific to either the most- or the least-contaminated site. This variation in species may account for the difference in vesicle abundance between sites. The consistently heavy AM colonisation of T. polytrichus found suggests that these fungi are not inhibited by soil heavy metals at these sites, and that the host derives some benefit from its AM symbiont.     

Diversity and community structure of ectomycorrhizal fungi in <Emphasis Type="Italic">Pinus thunbergii</Emphasis> coastal forests in the eastern region of Korea

We investigated the diversity and community structure of ectomycorrhizal (EcM) fungi in Pinus thunbergii stands on the eastern coast of Korea. We established two 10 × 10-m plots in six forest stands and sampled soil blocks containing rootlets of mature P. thunbergii trees. EcM roots were classified into morphological groups, and the fungal taxa associated with each morphotype were identified by sequencing the nuclear rDNA internal transcribed spacer region. Cenococcum geophilum and the Atheliales, Clavulinaceae, Russulaceae and Thelephoraceae species were the main members of the EcM fungal community, which included a total of 68 observed fungal taxa. As a whole, the community consisted of a few dominant fungal taxa, such as C. geophilum (28.6% relative abundance), and a large number of rare fungal taxa that showed low abundances and local distributions. Colonization patterns at the local site scale and at the scale of the study plots greatly differed among the EcM fungal taxa; C. geophilum was distributed extensively and was dominant in several study sites, whereas a certain Lactarius sp. was distributed locally but dominated in a given study site. We conclude with a discussion of the relationship between colonization patterns of EcM fungi and soil and environmental conditions.     

Mycorrhizal fungal community composition in seven orchid species inhabiting Song Mountain,Beijing, China

Mycorrhizal fungi play an important role in the germination and growth of orchids essentially influencing their survival,abundance, and spatial distribution. In this study, we investigated the composition of the mycorrhizal fungal community in seven terrestrial orchid species inhabiting Song Mountain, Beijing, China, using Illumina MiSeq high-throughput sequencing. The mycorrhizal communities in the seven orchids were mainly composed of members of the Ceratobasidiaceae, Sebacinales, and Tulasnellaceae, while a number of ectomycorrhizal fungi belonging to the Russulaceae, Tricholomataceae, Thelephoraceae, and Cortinariaceae were occasionally observed. However, the dominant fungal associates and mycorrhizal community differed significantly among the orchid species as well as subhabitats. These findings confirm the previous observation that sympatric orchid species show different preferences for mycorrhizal fungi, which may drive niche partitioning and contribute to their cooccurrence.     

Host Associations Between Fungal Root Endophytes and Boreal Trees

Fungal root endophytes colonize root tissue concomitantly with mycorrhizal fungi, but their identities and host preferences are largely unknown. We cultured fungal endophytes from surface-sterilized Cenococcum geophilum ectomycorrhizae of Betula papyrifera, Abies balsamea, and Picea glauca from two boreal sites in eastern Canada. Isolates were initially grouped on the basis of cultural morphology and then identified by internal transcribed spacer ribosomal DNA sequencing or by PCR restriction fragment length polymorphism. Phylogenetic analysis of the sequence data revealed 31 distinct phylotypes among the isolates, comprising mainly members of the ascomycete families Helotiaceae, Dermateaceae, Myxotrichaceae, and Hyaloscyphaceae, although other fungi were also isolated. Multivariate analyses indicate a clear separation among the endophyte communities colonizing each host tree species. Some phylotypes were evenly distributed across the roots of all three host species, some were found preferentially on particular hosts, and others were isolated from single hosts only. The results indicate that fungal root endophytes of boreal trees are not randomly distributed, but instead form relatively distinct assemblages on different host tree species.     

Global sampling of plant roots expands the described molecular diversity of arbuscular mycorrhizal fungi

We aimed to enhance understanding of the molecular diversity of arbuscular mycorrhizal fungi (AMF) by building a new global dataset targeting previously unstudied geographical areas. In total, we sampled 96 plant species from 25 sites that encompassed all continents except Antarctica. AMF in plant roots were detected by sequencing the nuclear SSU rRNA gene fragment using either cloning followed by Sanger sequencing or 454-sequencing. A total of 204 AMF phylogroups (virtual taxa, VT) were recorded, increasing the described number of Glomeromycota VT from 308 to 341 globally. Novel VT were detected from 21 sites; three novel but nevertheless widespread VT (Glomus spp. MO-G52, MO-G53, MO-G57) were recorded from six continents. The largest increases in regional VT number were recorded in previously little-studied Oceania and in the boreal and polar climatic zones — this study providing the first molecular data from the latter. Ordination revealed differences in AM fungal communities between different continents and climatic zones, suggesting that both biogeographic history and environmental conditions underlie the global variation of those communities. Our results show that a considerable proportion of Glomeromycota diversity has been recorded in many regions, though further large increases in richness can be expected in remaining unstudied areas.     

Diversity and persistence of arbuscular mycorrhizas in a low-Arctic meadow habitat

Little is known about the ecology and diversity of arbuscular mycorrhizal (AM) fungi in Arctic ecosystems. Here, the diversity and composition of the AM fungal community and its response to host plant community composition were studied in a low-Arctic meadow habitat. The natural vegetation in two low-Arctic meadow sites was manipulated. Plots with natural vegetation, monoculture and no vegetation were established. Seeds of Solidago virgaurea were sown into the plots and the AM fungal community in the seedling roots was analysed using the terminal restriction fragment length polymorphism (T-RFLP) method. The vegetation manipulation treatments affected the community composition but not the diversity of AM fungi found in S. virgaurea roots. The diversity of AM fungi was higher in S. virgaurea roots in the site with naturally higher plant species diversity. These results show that AM fungi in low-Arctic meadows are able to survive for a period of 2 yr without a host plant. This ability buffers the AM fungal community against short-term changes in host plant community composition and diversity.     

Fungus diversity in revegetated paddocks compared with remnant woodland in a south‐eastern Australian agricultural landscape

Summary Despite the importance of fungi for restoration, their presence in revegetated sites has received little attention. We compared the diversity and composition of macrofungi (i.e. those that form fleshy mushrooms and truffles) in 12 sites where 3‐to‐6‐year‐old native trees and shrubs had been planted (woodland restoration sites), with that in six woodland remnants. All sites were within an agricultural landscape near Holbrook in New South Wales. Of 58 fungal genera recorded, 57% occurred in woodland restoration sites and 83% in nearby patches of remnant woodland. Of the genera found in restoration sites, 70% were also found in the woodland remnants. The dominance of early successional genera such as Lacceria and Scleroderma in restoration sites suggests windblown colonisation by fungi. The reduced proportion of hypogeous genera (truffles) that rely on mammal vectors, which are less likely to occur in the restoration sites, also supports the view that most fungi occurred in restoration through colonisation rather than being generated from soil spores. Greatest overall fungal diversity occurred in large remnants that had greater structural complexity. Across all sites, epigeous genera (mushrooms) were most common (78% of all taxa collected across 46 genera) and of the nutritional modes, mycorrhizal genera (forming symbiotic associations with plants) were the most common (206 collections, 71%, 25 genera). Both hypogeous and mycorrhizal fungi were positively associated with the diversity of native forb species (wildflowers), suggesting that lower fungal diversity in restoration sites is likely to be a consequence of long‐term agricultural practices, particularly fertilizer use.     

Molecular diversity of arbuscular mycorrhizal fungi and patterns of host association over time and space in a tropical forest

We have used molecular techniques to investigate the diversity and distribution of the arbuscular mycorrhizal (AM) fungi colonizing tree seedling roots in the tropical forest on Barro Colorado Island (BCI), Republic of Panama. In the first year, we sampled newly emergent seedlings of the understory treelet Faramea occidentalis and the canopy emergent Tetragastris panamensis, from mixed seedling carpets at each of two sites. The following year we sampled surviving seedlings from these cohorts. The roots of 48 plants were analysed using AM fungal-specific primers to amplify and clone partial small subunit (SSU) ribosomal RNA gene sequences. Over 1300 clones were screened for random fragment length polymorphism (RFLP) variation and 7% of these were sequenced. Compared with AM fungal communities sampled from temperate habitats using the same method, the overall diversity was high, with a total of 30 AM fungal types identified. Seventeen of these types have not been recorded previously, with the remainder being similar to types reported from temperate habitats. The tropical mycorrhizal population showed significant spatial heterogeneity and nonrandom associations with the different hosts. Moreover there was a strong shift in the mycorrhizal communities over time. AM fungal types that were dominant in the newly germinated seedlings were almost entirely replaced by previously rare types in the surviving seedlings the following year. The high diversity and huge variation detected across time points, sites and hosts, implies that the AM fungal types are ecologically distinct and thus may have the potential to influence recruitment and host composition in tropical forests.