Article
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Despite the importance of ectomycorrhizal (ECM) fungi in forest ecosystems, knowledge about the ecological and co-evolutionary mechanisms underlying ECM host associations remains limited. Using a widely distributed group of ECM fungi known to form tight associations with trees in the family Pinaceae, we characterized host specificity among three unique Suillus–host species pairs using a combination of field root tip sampling and experimental bioassays. We demonstrate that the ECM fungus S. subaureus can successfully colonize Quercus hosts in both field and glasshouse settings, making this species unique in an otherwise Pinaceae-specific clade. Importantly, however, we found that the colonization of Quercus by S. subaureus required co-planting with a Pinaceae host. While our experimental results indicate that gymnosperms are required for the establishment of new S. subaureus colonies, Pineaceae hosts are locally absent at both our field sites. Given the historical presence of Pineaceae hosts before human alteration, it appears the current S. subaureus–Quercus associations represent carryover from past host presence. Collectively, our results suggest that patterns of ECM specificity should be viewed not only in light of current forest community composition, but also as a legacy effect of host community change over time.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... The sister abietoid clade, which contains ECM host genera such as Abies and Tsuga, has not been documented to host Suillus fungi. Although these genuslevel patterns of Suillus host specificity are well recognized from an evolutionary perspective (Nguyen et al. 2016), the specificity of ECM fungi has been shown to be ecologically context dependent Bogar and Kennedy 2013;Moeller et al. 2015;Lofgren et al. 2018). Specifically, the neighborhood in which plants are present may shift patterns of host specificity through colonization of alternative hosts via mycelial spread. ...
... This phenomenon was well documented by Massicotte et al. (1994), who found that Rhizopogon species were able to associate with hosts including Abies grandis, Tsuga heterophylla, Pseudotsuga menziesii, and Picea sitchensis, but only when they were co-planted with Pinus ponderosa seedlings. More recently, a similar pattern was documented with Suillus subaureus, where Lofgren et al. (2018) found that ECM colonization of S. subaureus on Quercus seedlings required co-planting with a Pinaceae host (Pinus strobus). In both cases, the presence of a "primary" host was shown to be required for the germination of Rhizopogon or Suillus spores ahead of mycelial colonization on "secondary" hosts. ...
... In cases where ECM fungal colonization does occur on secondary hosts, the extent to which these associations can be considered ecologically stable in the long term is unclear, although our work here and elsewhere (Lofgren et al. 2018) showed that at last three members of the genus Suillus (S. subaureus, S. punctatipes, and S. glandulosus) can associate with alternative hosts. It is possible that the colonization of secondary hosts be greatly facilitated by carbohydrate flow from the primary host into the fungal mycelium (Finlay 1989), and if the primary host is eliminated, secondary host colonization might significantly decline. ...
Article
Full-text available
Suillus is among the best-known examples of an ectomycorrhizal (ECM) fungal genus that demonstrates a high degree of host specificity. Currently recognized host genera of Suillus include Larix, Pinus, and Pseudotsuga, which all belong to the pinoid clade of the family Pinaceae. Intriguingly, Suillus sporocarps have been sporadically collected in forests in which known hosts from these genera are locally absent. To determine the capacity of Suillus to associate with alternative hosts in both the pinoid and abietoid clades of Pinaceae, we examined the host associations of two Suillus species (S. punctatipes and S. glandulosus) through field-based root tip sampling and seedling bioassays. Root tip collections underneath Suillus sporocarps were molecularly identified (fungi: nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 [ITS barcode]; plant: trnL) to assess the association with multiple hosts. The bioassays contained both single- and two-species treatments, including a primary (Larix or Pseudotsuga) and a secondary (Picea, Pinus, or Abies) host. For the S. punctatipes bioassay, an additional treatment in which the primary host was removed after 8 mo was included to assess the effect of primary host presence on longer-term ECM colonization. The field-based results confirmed that Suillus fungi were able to associate with Abies and Tsuga hosts, representing novel host genera for this genus. In the bioassays, colonization on the primary hosts was detected in both single- and two-species treatments, but no colonization was present when Picea and Abies hosts were grown alone. Removal of a primary host had no effect on percent ECM colonization, suggesting that primary hosts are not necessary for sustaining Suillus colonization once they are successfully established on secondary hosts. Collectively, our results indicate that host specificity is more flexible in this genus than previously acknowledged and help to explain the presence of Suillus in forests where recognized hosts are not present.
... We recently became interested in the aforementioned tradeoffs to help understand the enigmatic life history strategy of the ECM fungus, Suillus subaureus. Unlike other Suillus species, which are largely host-specific to one of three different host genera in the family Pinaceae [31], S. subaureus is able to colonize both Pinus and Quercus host species [32]. However, this expansion of host range is complicated by the fact that the spores of S. subaureus will only germinate in the presence of Pinaceae host [32]. ...
... Unlike other Suillus species, which are largely host-specific to one of three different host genera in the family Pinaceae [31], S. subaureus is able to colonize both Pinus and Quercus host species [32]. However, this expansion of host range is complicated by the fact that the spores of S. subaureus will only germinate in the presence of Pinaceae host [32]. As such, the establishment on Quercus individuals requires spread of S. subaureus mycelium growing from colonized Pinaceae root tips. ...
... Under those nearby Pinus individuals, we have encountered other Suillus species but never encountered S. subaureus despite extensive searching. Thus, it appears that the presence of S. subaureus on Quercus hosts represents a legacy effect of Pinus individuals that are no longer present [32]. Further, in our extensive collecting of Suillus throughout Minnesota, USA, we have regularly encountered many other Suillus species in Pinus forests, but only S. subaureus in two locations. ...
Article
Full-text available
Two common ecological assumptions are that host generalist and rare species are poorer competitors relative to host specialist and more abundant counterparts. While these assumptions have received considerable study in both plant and animals, how they apply to ectomycorrhizal fungi remains largely unknown. To investigate how interspecific competition may influence the anomalous host associations of the rare ectomycorrhizal generalist fungus, Suillus subaureus, we conducted a seedling bioassay. Pinus strobus seedlings were inoculated in single- or two-species treatments of three Suillus species: S. subaureus, S. americanus, and S. spraguei. After 4 and 8 months of growth, seedlings were harvested and scored for mycorrhizal colonization as well as dry biomass. At both time points, we found a clear competitive hierarchy among the three ectomycorrhizal fungal species: S. americanus > S. subaureus > S. spraguei, with the competitive inferior, S. spraguei, having significantly delayed colonization relative to S. americanus and S. subaureus. In the single-species treatments, we found no significant differences in the dry biomasses of P. strobus seedlings colonized by each Suillus species, suggesting none was a more effective plant symbiont. Taken together, these results indicate that the rarity and anomalous host associations exhibited by S. subaureus in natural settings are not driven by inherently poor competitive ability or host growth promotion, but that the timing of colonization is a key factor determining the outcome of ectomycorrhizal fungal competitive interactions.
... Subsequent management practices, such as clear-cut logging, usually enhance these changes as a possible consequence of soil mechanical damage (Ford et al., 2018;Vašutová et al., 2018). The main driver of fungal community shifts is the death of mature trees Treu et al., 2014), because ECM fungi are obligate symbionts unable to live without their hosts (Baldrian, 2009;Lofgren et al., 2018). This results in an extinction of ECM fungal species associated with mature trees (= late-successional ECM fungi), while early-successional ECM fungi, with a low demand on photosynthates, survive on seedlings (Egli et al., 2002;Vašutová et al., 2018;Veselá et al., 2019b). ...
... On the other hand, almost all host tree species harbor in their symbiotic fungal assembly genusrestricted ECM fungi, which provide them exclusive access to resources (Molina et al., 1992). Nevertheless, ECM fungi with a broad host range may also show host preference depending on the ecological context (Lang et al., 2011), while genus-restricted ECM fungi may expand their host range in the absence of their primary host (Lofgren et al., 2018). ...
... Subsequent management practices, such as clear-cut logging, usually enhance these changes as a possible consequence of soil mechanical damage (Ford et al., 2018;Vašutová et al., 2018). The main driver of fungal community shifts is the death of mature trees Treu et al., 2014), because ECM fungi are obligate symbionts unable to live without their hosts (Baldrian, 2009;Lofgren et al., 2018). This results in an extinction of ECM fungal species associated with mature trees (= late-successional ECM fungi), while early-successional ECM fungi, with a low demand on photosynthates, survive on seedlings (Egli et al., 2002;Vašutová et al., 2018;Veselá et al., 2019b). ...
... On the other hand, almost all host tree species harbor in their symbiotic fungal assembly genusrestricted ECM fungi, which provide them exclusive access to resources (Molina et al., 1992). Nevertheless, ECM fungi with a broad host range may also show host preference depending on the ecological context (Lang et al., 2011), while genus-restricted ECM fungi may expand their host range in the absence of their primary host (Lofgren et al., 2018). ...
Article
Full-text available
Due to ongoing climate change, forests are expected to face significant disturbances more frequently than in the past. Appropriate management is intended to facilitate forest regeneration. Because European temperate forests mostly consist of trees associated with ectomycorrhizal (ECM) fungi, understanding their role in these disturbances is important to develop strategies to minimize their consequences and effectively restore forests. Our aim was to determine how traditional (EXT) and nonintervention (NEX) management in originally Norway spruce (Picea abies) forests with an admixture of European larch (Larix decidua) affect ECM fungal communities and the potential to interconnect different tree species via ECM networks 15 years after a windstorm. Ten plots in NEX and 10 plots in EXT with the co-occurrences of Norway spruce, European larch, and silver birch (Betula pendula) were selected, and a total of 57 ECM taxa were identified using ITS sequencing from ECM root tips. In both treatments, five ECM species associated with all the studied tree species dominated, with a total abundance of approximately 50% in the examined root samples. Because there were no significant differences between treatments in the number of ECM species associated with different tree species combinations in individual plots, we concluded that the management type did not have a significant effect on networking. However, management significantly affected the compositions of ECM symbionts of Norway spruce and European larch but not those of silver birch. Although this result is explained by the occurrence of seedlings and ECM propagules that were present in the original forest, the consequences are difficult to assess without knowledge of the ecology of different ECM symbionts.
... Similarly, ectomycorrhizal (ECM) fungi can display a broad host range (Marx and Krupa, 1978), although many have well recognized host specificity (Molina et al., 1992;Lofgren et al., 2018). Ectomycorrhizal fungi are associated with plant species along a host spectrum from broad to narrow (Molina et al., 1992). ...
Article
Black Locust (Robinia pseudoacacia L.) is a woody legume with a worldwide distribution. Its ecological and economical importance is largely due to fast growth and dinitrogen (N2)-fixation ability with rhizobia. These features make Black Locust suitable as a model species for other woody legumes as well. However, its symbiotic association with mycorrhizal fungi has not gained much attention. The small body of literature published indicates that this mycorrhizal association interacts with symbiotic N2-fixation, greatly enhancing the ecological and physiological performance of Black Locust by improving its rate of growth, nutrition status and resistance to stress conditions, such as drought and salt and heavy metal accumulation. Here we summarize the current knowledge on the benefits of the association of Black Locust with arbuscular mycorrhizal fungi with the aim of providing future research directions on how this symbiotic partnership is involved in a tripartite symbiotic association including rhizobia. This association is of particular importance considering both the invasive nature of Black Locust, its economic and cultural importance and its use in restoration of degraded or contaminated landscapes.
... Strict host specificity is rare in ECM fungi (Churchland & Grayston, 2014), and many ECM fungi can simultaneously colonise dozens of plants (Horton & van der Heijden, 2008). Interestingly, recent evidence also illustrated that ECM host specificity patterns depend on the mode of colonisation (Lofgren, Nguyen, & Kennedy, 2018), and that tree genetics influences the composition of ECM communities (Gehring, Sthultz, Flores-Rentería, Whipple, & Whitham, 2017). A low specificity can provide plants with a competitive advantage in the uptake of nutrients in comparison to non-host species, or plant species with a high specificity. ...
Chapter
Trees can be associated with dozens of fungi helping them to acquire resources from forest soils. The most widespread mutualistic association in boreal and temperate forests is the ectomycorrhizal symbiosis. This symbiosis involves mushroom-forming fungi of basidiomycota, ascomycota, and some zygomycota clades and the roots of woody plant species, including oaks, poplars or pines. Although the impact of this association on ecosystem production and tree nutrition is investigated for about a century, our understanding on the molecular mechanisms that control water and nutrient fluxes between plant and fungal partners is still limited. Here, we review the recent knowledge on the ectomycorrhizal contribution to tree nutrition. We specifically highlight the molecular mechanisms driving the acquisition, translocation and release of water and nutrients in ectomycorrhizal systems. We particularly focus on the transport of macronutrients, including nitrogen, phosphorus, potassium, sulphur and calcium, micronutrients, and water by the symbiotic partner. We also provide background on the evolution, diversity, and importance of this symbiosis, identify knowledge gaps, and propose future research directions.
... Among fungi, many are specific to particular families or genera of plants (Molina and Horton 2015); among plants, although strict specificity to one or a few species of fungi is almost entirely restricted to mycoheterotrophs (Bruns et al. 2002), the suite of symbionts a plant supports often varies predictably with plant taxonomy (Molina and Horton 2015). In many cases, this specificity may be exerted at the spore germination stage: Host-specific fungi will not germinate until appropriate roots are present, despite being capable of broader associations as hyphae (Massicotte et al. 1994;Lofgren et al. 2018). Additionally, recent research into ectomycorrhizal fungal gene expression has identified many small secreted peptides that appear to be expressed at the initiation of symbiosis, and whose identities can vary considerably among fungal taxa (Plett et al. 2011;Liao et al. 2016). ...
Article
Full-text available
Although ectomycorrhizal fungi have well-recognized effects on ecological processes ranging from plant community dynamics to carbon cycling rates, it is unclear if plants are able to actively influence the structure of these fungal communities. To address this knowledge gap, we performed two complementary experiments to determine (1) whether ectomycorrhizal plants can discriminate among potential fungal partners, and (2) to what extent the plants might reward better mutualists. In experiment 1, split-root Larix occidentalis seedlings were inoculated with spores from three Suillus species (S. clintonianus, S. grisellus, and S. spectabilis). In experiment 2, we manipulated the symbiotic quality of Suillus brevipes isolates on split-root Pinus muricata seedlings by changing the nitrogen resources available, and used carbon-13 labeling to track host investment in fungi. In experiment 1, we found that hosts can discriminate in multi-species settings. The split-root seedlings inhibited colonization by S. spectabilis whenever another fungus was available, despite similar benefits from all three fungi. In experiment 2, we found that roots and fungi with greater nitrogen supplies received more plant carbon. Our results suggest that plants may be able to regulate this symbiosis at a relatively fine scale, and that this regulation can be integrated across spatially separated portions of a root system.
... Strict host specificity is rare in ECM fungi (Churchland & Grayston, 2014), and many ECM fungi can simultaneously colonise dozens of plants (Horton & van der Heijden, 2008). Interestingly, recent evidence also illustrated that ECM host specificity patterns depend on the mode of colonisation (Lofgren, Nguyen, & Kennedy, 2018), and that tree genetics influences the composition of ECM communities (Gehring, Sthultz, Flores-Rentería, Whipple, & Whitham, 2017). A low specificity can provide plants with a competitive advantage in the uptake of nutrients in comparison to non-host species, or plant species with a high specificity. ...
... In agreement with these findings, we found the genus Russula to be the second most abundant genus associated with the four different hosts ( Figure S5). An example of host expansion triggered by past presence of other tree species in the stand, was shown for Suillus subaureus (Lofgren, Nguyen, & Kennedy, 2018). Nevertheless, in our study, we found Suillus granulatus and Suillus viscidus exclusively on roots of the two conifers, Pinus and Larix respectively (Figure 1a). ...
Article
The mutualistic symbiosis between forest trees and ectomycorrhizal fungi (EMF) is among the most ubiquitous and successful interactions in terrestrial ecosystems. Specific species of EMF are known to colonize specific tree species, benefitting from their carbon source, and in turn, improving their access to soil water and nutrients. EMF also form extensive mycelial networks that can link multiple root‐tips of different trees. Yet the number of tree species connected by such mycelial networks, and the traffic of material across them, are just now under study. Recently we reported substantial belowground carbon transfer between Picea, Pinus, Larix and Fagus trees in a mature forest. Here we analyze the EMF community of these same individual trees and identify the most likely taxa responsible for the observed carbon transfer. Among the nearly 1200 EMF root‐tips examined, 50‐70% belong to operational taxonomic units (OTUs) that were associated with 3 or 4 tree host species, and 90% of all OTUs were associated with at least two tree species. Sporocarp 13C signals indicated that carbon originating from labeled Picea trees was transferred among trees through EMF networks. Interestingly, phylogenetically more closely related tree species exhibited more similar EMF communities and exchanged more carbon. Our results show that belowground carbon transfer is well orchestrated by the evolution of EMFs and tree symbiosis.
... Diversification associated with host shifting seen in younger clades, like R. peckii, may be driven by the inability of certain populations to track changing host distributions. Host switching could emerge as a legacy effect from relictual inoculum persisting in soil, allowing opportunistic contact with non-native hosts (Lofgren et al., 2018). ...
Article
Numerous lineages of mushroom-forming fungi have been subject to bursts of diversification throughout their evolutionary history, events that can impact our ability to infer well-resolved phylogenies. However, groups that have undergone quick genetic change may have the highest adaptive potential. As the second largest genus of mushroom-forming fungi, Russula provides an excellent model for studying hyper-diversification and processes in evolution that drives it. This study focuses on the morphologically defined group – Russula subsection Roseinae. Species hypotheses based on morphological differentiation and multi-locus phylogenetic analyses are tested in the Roseinae using different applications of the multi-species coalescent model. Based on this combined approach, we recognize fourteen species in Roseinae including the Albida and wholly novel Magnarosea clades. Reconstruction of biogeographic and host association history suggest that parapatric speciation in refugia during glacial cycles of the Pleistocene drove diversification within the Roseinae, which is found to have a Laurasian distribution with an evolutionary origin in the Appalachian Mountains of eastern North America. Finally, we detect jump dispersal at a continental scale that has driven diversification since the most recent glacial cycles.
... An ecological difference can serve as a taxonomic character to distinguish novel species. Although the host preference/specificity of mycorrhizal fungi is complex and needs both field surveys and in vitro mycorrhizal synthesis assays using mycelia and basidiospores to evaluate accurately (Lofgren et al., 2018; Pérez-Pazos et al., 2021), our observations and molecular analyses of mycorrhizae demonstrated that S. flavorhizomorphae prefers pines whereas S. chloroporum prefers broadleaved trees in Betulaceae (Carpinus) and Fagaceae (Castanopsis and Quercus). This suggests that different species in this genus have different host preferences. ...
Article
We describe two new species of resupinate Sistotrema sensu lato (Cantharellales) collected in Japan: S. flavorhizomorphae and S. chloroporum. Both species have urniform basidia with more than four sterigmata and monomitic hyphal system, oil-rich hyphae in subiculum, which is typical for this genus. Sistotrema chloroporum is characterized by poroid hymenophore partly yellowish-green, basidia 4-6-spored, medium-sized basidiospores (4.5-6.5 × 3.5-6 µm), and broadleaf forest habitat. Sistotrema flavorhizomorphae is characterized by hydnoid-irpicoid hymenophore, bright yellowish rhizomorphs, basidia 6-8-spored, small basidiospores (3-3.5 × 2.5-3 µm), and pine forest habitat. Phylogenetic trees inferred from the fungal nrDNA ITS and LSU and the rpb2 sequences supported that both species were distinct and grouped with other ectomycorrhizal Sistotrema and Hydnum species, but their generic boundary was unclear. Mycorrhizae underneath basidiomes of both species were identified and described via molecular techniques. Mycorrhizae of S. chloroporum have similar characteristics to those of other Sistotrema s.l. and Hydnum species, i.e., S. confluens and H. repandum, whereas S. flavorhizomorphae has a distinct morpho-anatomy, for example, a distinct pseudoparenchymatous mantle. Comprehensive characterizations of basidiomes and mycorrhizae improve the taxonomic analysis of mycorrhizal species of Sistotrema s.l.
... Agricultural trials showed that Serendipita vermifera was unable to move 16 cm through the soil to colonize nearby species during an 8 week experiment (Ray et al., 2018). Given that OMF are thought to occupy niches along a continuum from soil saprotrophs to root endophytes (Selosse et al., 2018), and that there is growing evidence that some fungi associate with particular hosts (Lofgren et al., 2018;Martino et al., 2018), it will be important to design sampling procedures specific to orchid mycorrhizal fungi as they may also associate with particular hosts other than orchids. These procedures may need to include identifying the optimal season (as some fungi may be seasonally undetectable at low quantities in the soil) and the inclusion of host plant roots in the sampling design as is used for other root endophytes. ...
Article
Background and aims: In orchid conservation, quantifying the specificity of mycorrhizal associations, and establishing which orchid species use the same fungal taxa, is important for sourcing suitable fungi for symbiotic propagation and selecting sites for conservation translocation. For Caladenia subgenus Calonema (Orchidaceae), which contains 58 threatened species, we ask: (1) How many taxa of Serendipita mycorrhizal fungi do threatened species of Caladenia associate with? (2) Do threatened Caladenia share orchid mycorrhizal fungi with common Caladenia? (3) How geographically widespread are mycorrhizal fungi associated with Caladenia? Methods: Fungi were isolated from 127 Caladenia species followed by DNA sequencing of the ITS sequence locus. We used a 4.1- 6 % sequence divergence cut-off range to delimit Serendipita Operational Taxonomic Units (OTUs). We conducted trials testing the ability of fungal isolates to support germination and plant growth. A total of 597 Serendipita isolates from Caladenia, collected from across the Australian continent, were used to estimate the geographic range of OTUs. Results: Across the genus, Caladenia associated with 10 OTUs of Serendipita (Serendipitaceae) mycorrhizal fungi. Specificity was high, with 19 of the 23 threatened Caladenia species sampled in detail associating solely with OTU A, which supported plants from germination to adulthood. The majority of populations of Caladenia associated with one OTU per site. Fungal sharing was extensive, with 62 of the 79 Caladenia sampled in subgenus Calonema associating with OTU A. Most Serendipita OTUs were geographically widespread. Conclusions: Mycorrhizal fungi can be isolated from related common species to propagate threatened Caladenia. Because of high specificity of most Caladenia species, only small numbers of OTUs typically need to be considered for conservation translocation. When selecting translocation sites, the geographic range of the fungi is not a limiting factor, and using related Caladenia species to infer the presence of suitable fungal OTUs may be feasible.
... For example, the Larix specialist Suillus larcinus was detected on a Betula sapling when growing next to a Larix sapling(Nara, 2006).In another study it was shown that Suillus subaureus can germinate and associate with both Pinus and Quercus hosts, both in the laboratory and in the forest. Two other fungi, Suillus americanus and Suillus clintonianus, germinated by spores only in the presence of their primary Pinus hosts but could also form mycorrhizal association with Quercus and Larix trees when colonizing via mycelial networks(Lofgren et al., 2018). ...
Article
Mycorrhizal fungi can colonize multiple trees of a single or multiple taxa, facilitating bidirectional exchange of carbon between trees. Mycorrhiza‐induced carbon transfer was shown in the forest, but it is unknown whether carbon is shared symmetrically among tree species, and if not, which tree species are better donors and which are better recipients. Here we test this question by investigating carbon transfer dynamics among five Mediterranean tree species in a microcosm system, including both ectomycorrhizal (EM) and arbuscular (AM) plants. Trees were planted together in 'community boxes' using natural soil from a mixed forest plot that serves as habitat for all five tree species and their native mycorrhizal fungi. In each box, only the trees of a single species were pulse‐labeled with 13CO2. We found that carbon transfer was asymmetric, with oak being a better donor, and pistacia and cypress better recipients. Shared mycorrhizal species may have facilitated carbon transfer, but their diversity did not affect the amount, nor timing, of the transfer. Overall, our findings in a microcosm system expose rich, but hidden, belowground interactions in a diverse population of trees and mycorrhizal fungi. The asymmetric carbon exchange among co‐habiting tree species could potentially contribute to forest resilience in an uncertain future.
... Restoration efforts often involve controlling invasive species (Weidlich et al. 2020), which may rely on mutualists (Vogelsang & Bever 2009;Moyano et al. 2020), but little is known about the consequences of having exotic soil microbiota in areas where exotic plants have been removed. For ECMs, interactions between native plants and exotic fungi do not necessarily cease after the removal of exotic plant species (Lofgren et al. 2018). ...
Article
As restoration ecology begins to engage more formally with the role of belowground interactions, we note that there is an even greater gap in knowledge of the role ectomycorrhizae (ECMs) have in ecological restoration in the neotropical region. Even though there are a few records of ECMs in the Neotropics not much is known about their function. Here we highlight This article is protected by copyright. All rights reserved. the underestimated importance of ECMs in neotropical coastal zones, discuss how we could use the vegetation on the coast of the Atlantic Forest, called restinga, as a model to investigate tropical ECMs, and explore further possibilities that can be used in restoration projects.
... As the strain tested in this study was isolated from the roots of green alder (Alnus crispa (Aiton) Pursh; accepted name Alnus viridis ssp. crispa (Aiton) Turrill) (see Supplementary Table S1), 1 this might explain the absence of a beneficial effect of the P. fortinii inoculation treatment, as previously reported (Bruns et al. 2002;Lofgren et al. 2018). Future experiments should also aim to test if the effect of P. fortinii is "host dependent". ...
Article
Full-text available
Plants maintain beneficial mutualistic relationships with the mycobiont communities found in their rhizosphere, leading to an increase in plant productivity and health. In nutrient-depleted substrates like mine tailings, mycobiont inoculation is often recommended to help restore a successful plant cover. Our 15-week greenhouse experiment aimed to assess the individual effects of a dark septate endophyte (Phialocephala fortinii C.J.K. Wang & H.E. Wilcox #4 (KX611529)) and two Helotiales strains (Rhizoscyphus ericae (D.J. Read) W.Y. Zhuang & Korf #22 (EU221877) and Meliniomyces sp. #1 (KT275679)) on the growth of plane-leaved willow (Salix planifolia Pursh) cuttings on sterilized and unsterilized waste rock. Rhizoscyphus ericae increased shoot biomass of cuttings on sterilized waste rock, whereas Meliniomyces sp. had a positive effect on cuttings grown on unsterilized waste rock. However, P. fortinii strain had no effect on the survival rate, shoot production, and biomass production of S. planifolia cuttings. This study demonstrates that controlled inoculation with ecologically well-adapted mycobionts could promote plant establishment and productivity on abandoned waste rock and could be an efficient and integrated biotechnological approach for ecological restoration of Canadian mining boreal ecosystems.
... Host associations with both subgenera of Pinus are reported for S. flavidus and S. acidus but should be further verified. For the North American S. subaureus, an initial association with Pinus subgenus Strobus is required for transferring into Quercus in later developmental stage, therefore Quercus was not included in the BayesTraits analysis (Lofgren et al., 2018). Further, Suillus sinuspaulianus was also excluded from the host reconstruction due to the uncertainty of its host association (Pomerleau and Smith, 1962;Kretzer et al., 1996). ...
Article
Full-text available
Suillus is a genus of ectomycorrhizal fungi associated almost exclusively with Pinaceae. Lack of sample collections in East Asia and unresolved basal phylogenetic relationships of the genus are the major obstacles for better understanding the Suillus evolution. A resolved phylogeny of Suillus representing global diversity was achieved by sequencing multiple nuclear ribosomal and protein coding genes and extensive samples collected in East Asia. Fungal fossils are extremely rare, and the Eocene ectomycorrhizal symbiosis (ECM) fossil of Pinus root has been widely used for calibration. This study explored an alternative calibration scenario of the ECM fossil for controversy. Ancestral host associations of Suillus were estimated by maximum likelihood and Bayesian Markov chain Monte Carlo (MCMC) analyses, inferred from current host information from root tips and field observation. Host shift speciation explains the diversification of Suillus major clades. The three basal subgenera of Suillus were inferred to be associated with Larix, and diverged in early Eocene or Upper Cretaceous. In the early Oligocene or Paleocene, subgenus Suillus diverged and switched host to Pinus subgenus Strobus, and then switched to subgenus Pinus four times. Suillus subgenus Douglasii switched host from Larix to Pseudotsuga in Oligocene or Eocene. Increased species diversity occurred in subgenus Suillus after it switched host to Pinus but no associated speciation rate shifts were detected. Ancestral biogeographic distributions of Suillus and Pinaceae were estimated under the Dispersal Extinction Cladogenesis (DEC) model. Ancestral distribution patterns of Suillus and Pinaceae are related but generally discordant. Dispersals between Eurasia and North America explain the prevalence of disjunct Suillus taxa.
... There is still a need to strengthen the 'mycocentric perspective' (Fitter et al., 2000), because specificity in fungal-plant interactions (e.g. Lofgren et al., 2018; in this issue of New Phytologist, pp. 1273-1284) work both ways. ...
Article
Full-text available
Background Most species of the Russulaceae are ectomycorrhizal (ECM) fungi, which are widely distributed in different types of forest ecology and drive important ecological and economic functions. Little is known about the composition variation of the Russulaceae fungal community aboveground and in the root and soil during the growing season (June–October) from a Quercus mongolica forest. In this study, we investigated the changes in the composition of the Russulaceae during the growing season of this type of forest in Wudalianchi City, China. Methods To achieve this, the Sanger sequencing method was used to identify the Russulaceae aboveground, and the high-throughput sequencing method was used to analyze the species composition of the Russulaceae in the root and soil. Moreover, we used the Pearson correlation analysis, the redundancy analysis and the multivariate linear regression analysis to analyze which factors significantly affected the composition and distribution of the Russulaceae fungal community. Results A total of 56 species of Russulaceae were detected in the Q. mongolica forest, which included 48 species of Russula , seven species of Lactarius , and one species of Lactifluus . Russula was the dominant group. During the growing season, the sporocarps of Russula appeared earlier than those of Lactarius . The number of species aboveground exhibited a decrease after the increase and were significantly affected by the average monthly air temperature ( r = −0.822, p = 0.045), average monthly relative humidity ( r = −0.826, p = 0.043), monthly rainfall ( r = 0.850, p = 0.032), soil moisture ( r = 0.841, p = 0.036) and soil organic matter ( r = 0.911, p = 0.012). In the roots and soils under the Q. mongolica forest, the number of species did not show an apparent trend. The number of species from the roots was the largest in September and the lowest in August, while those from the soils were the largest in October and the lowest in June. Both were significantly affected by the average monthly air temperature ( r ² = 0.6083, p = 0.040) and monthly rainfall ( r ² = 0.6354, p = 0.039). Moreover, the relative abundance of Russula and Lactarius in the roots and soils showed a linear correlation with the relative abundance of the other fungal genera.
Article
While there has been significant progress characterizing the ‘symbiotic tool kit’ of ectomycorrhizal (ECM) fungi, how host specificity may be encoded into ECM fungal genomes remains poorly understood. We conducted a comparative genomic analysis of ECM fungal host specialists and generalists, focusing on the specialist genus Suillus. Global analyses of genome dynamics across 46 species were assessed, along with targeted analyses of three classes of molecules previously identified as important determinants of host specificity: small secreted proteins (SSPs), secondary metabolites (SMs), and G‐protein coupled receptors (GPCRs). Relative to other ECM fungi, including other host specialists, Suillus had highly dynamic genomes including numerous rapidly evolving gene families and many domain expansions and contractions. Targeted analyses supported a role for SMs but not SSPs or GPCRs in Suillus host specificity. Phylogenomic‐based ancestral state reconstruction identified Larix as the ancestral host of Suillus, with multiple independent switches between white and red pine hosts. These results suggest that like other defining characteristics of the ECM lifestyle, host specificity is a dynamic process at the genome level. In the case of Suillus, both SMs and pathways involved in the deactivation of reactive oxygen species appear to be strongly associated with enhanced host specificity.
Article
Ectomycorrhizal (ECM) fungi are closely related to vegetation compositions, edaphic properties, and site-specific processes. However, the coevolutionary mechanisms underlying the spatial distributions in floristic and ECM fungal composition in the context of biotic adaptations and abiotic variances remain unclear. We combine a total of 25 ECM fungus-associated environmental variables to impose three types of composite scores and then quantify the environmental gradients of geographical site, soil chemical property and vegetation functional trait across 122 grids of 20 m × 20 m in a 25-hm2 forest plot. Significant dissimilarities in vegetational and ECM fungal abundance and composition existed along the above environmental gradients. Specifically, a contrasting floristic distribution (e.g., Betula platyphylla vs. Tilia mandshurica) existed between the northeastern and southwestern areas and was closely related to the nutrient and moisture gradients (with high levels in the west and low levels in the east). Furthermore, the ECM fungal communities were more abundant in the nutrient-poor and low-moisture environments than in the nutrient-rich and high-moisture environments, and the mixed-forest in the middle-gradient sites between the northeastern and southwestern areas harbored the highest ECM fungal diversity. These findings suggest that predictable within-site vegetation succession is closely related to ECM-associated determinants and the natural spatial heterogeneity of edaphic properties at a local scale.
Article
Se evaluó el efecto de Scleroderma verrucosum (Vaill) Pers y Rhizopogon luteolus Fr. & Nordh. sobre la calidad morfológica y biológica de plantas de Pinus radiata D. Don en vivero en Vilcashuamán, Ayacucho, Perú. Tratamientos: (1) Micorrización con Scleroderma verrucosum, (2) Micorrización con Rhizopogon luteolus, (3) Mezcla de ambos hongos y (4) Control, en un diseño completamente al azar con 10 repeticiones por tratamiento. Los hongos provinieron de bosques de Pinus radiata y Eucalyptus globulus de la localidad. La inoculación se realizó en el repique a los 30 días de siembra y la evaluación a los 7.5 meses después del repique. Los pinos micorrizados superaron con diferencias significativas al control en todas las variables. En el diámetro del cuello y materia seca de la parte aérea de los inoculados no presentaron diferencias significativas; sin embargo, en altura, materia seca de la raíz y materia seca total destacó el tratamiento Mezcla. En la calidad biológica se observó mayor número de micorrizas en los inoculados, con diferencias significativas frente al control sin micorrizar. Se evidenció mayor porcentaje de micorrizas monopodiales (91%) en relación a los dicotómicos (8.5%) y coraloides (0.6%). Se determinaron relaciones positivas significativas entre las variables morfológicas, pero éstas sobre P. radiata presentaron asociaciones no significativas con el número de micorrizas. El uso individual y en mezcla de hongos ectomicorrízicos silvestres incrementó la calidad morfológica y biológica de P. radiata, por ello se recomienda la aplicación de estos hongos para la producción de plántulas en viveros de Vilcashuamán y otras zonas altoandinas.
Article
Full-text available
The genus Suillus represents one of the most recognizable groups of mushrooms in conifer forests throughout the Northern Hemisphere. Although for decades the genus has been relatively well defined morphologically, previous molecular phylogenetic assessments have provided important yet preliminary insights into its evolutionary history. Here we present the first large-scale phylogenetic study of the boundaries of each species in the genus Suillus based on the most current internal transcribed spacer (ITS) barcode sequences available in public databases, as well as sequencing of 224 vouchered specimens and cultures, 15 of which were type specimens from North America. We found that species boundaries delimited by morphological data are broadly congruent with those based on ITS sequences. However, some species appear to have been described several times under different names, several species groups cannot be resolved by ITS sequences alone, and undescribed taxa are apparent, especially in Asia. Therefore, we elevated S. tomentosus var. discolor to S. discolor; proposed synonymies of S. neoalbidipes with S. glandulosipes, S. borealis with S. brunnescens, Boletus serotinus, B. solidipes with Suillus elbensis, S. lactifluus with S. granulatus, S. himalayensis with S. americanus; and proposed usage of the names S. clintonianus in the place of the North American S. grevillei, S. weaverae for North American S. granulatus, S. ampliporus in the place of the North American S. cavipes, and S. elbensis in place of the North American S. viscidus We showed that the majority of Suillus species have strong affinities for particular host genera. Although deep node support was low, geographic differentiation was apparent, with species from North America, Eurasia, and Asia often forming their own clades. Collectively, this comprehensive genus-level phylogenetic integration of currently available Suillus ITS molecular data and metadata will aid future taxonomic and ecological work on an important group of ectomycorrhizal fungi.
Article
Full-text available
Ectomycorrhizal fungi (EMF) represent one of the major guilds of symbiotic fungi associated with roots of forest trees, where they function to improve plant nutrition and fitness in exchange for plant carbon. Many groups of EMF exhibit preference or specificity for different plant host genera; a good example is the genus Suillus, which grows in association with the conifer family Pinaceae. We investigated genetics of EMF host-specificity by cross-inoculating basidiospores of five species of Suillus onto ten species of Pinus, and screened them for their ability to form ectomycorrhizae. Several Suillus spp. including S. granulatus, S. spraguei, and S. americanus readily formed ectomycorrhizae (compatible reaction) with white pine hosts (subgenus Strobus), but were incompatible with other pine hosts (subge-nus Pinus). Metatranscriptomic analysis of inoculated roots reveals that plant and fungus each express unique gene sets during incompatible vs. compatible pairings. The Suillus-Pinus metatranscriptomes utilize highly conserved gene regulatory pathways, including fungal G-protein signaling, secretory pathways, leucine-rich repeat and pathogen resistance proteins that are similar to those associated with host-pathogen interactions in other plant-fungal systems. Metatranscriptomic study of the combined Suillus-Pinus transcrip-tome has provided new insight into mechanisms of adaptation and coevolution of forest trees with their microbial community, and revealed that genetic regulation of ectomycorrhi-zal symbiosis utilizes universal gene regulatory pathways used by other types of fungal-plant interactions including pathogenic fungal-host interactions. Author Summary Ectomycorrhizal fungi (EMF) comprise the dominant group of symbiotic fungi associated with plant roots in temperate and boreal forests. We examined host-specificity and gene-expression of five EMF Suillus species that exhibited strong patterns of mycorrhizal PLOS Genetics |
Article
Full-text available
Photosynthesis by leaves and acquisition of water and minerals by roots are required for plant growth, which is a key component of many ecosystem functions. Although the role of leaf functional traits in photosynthesis is generally well understood, the relationship of root functional traits to nutrient uptake is not. In particular, predictions of nutrient acquisition strategies from specific root traits are often vague. Roots of nearly all plants cooperate with mycorrhizal fungi in nutrient acquisition. Most tree species form symbioses with either arbuscular mycorrhizal (AM) or ectomycorrhizal (EM) fungi. Nutrients are distributed heterogeneously in the soil, and nutrient-rich “hotspots” can be a key source for plants. Thus, predicting the foraging strategies that enable mycorrhizal root systems to exploit these hotspots can be critical to the understanding of plant nutrition and ecosystem carbon and nutrient cycling. Here, we show that in 13 sympatric temperate tree species, when nutrient availability is patchy, thinner root species alter their foraging to exploit patches, whereas thicker root species do not. Moreover, there appear to be two distinct pathways by which thinner root tree species enhance foraging in nutrient-rich patches: AM trees produce more roots, whereas EM trees produce more mycorrhizal fungal hyphae. Our results indicate that strategies of nutrient foraging are complementary among tree species with contrasting mycorrhiza types and root morphologies, and that predictable relationships between below-ground traits and nutrient acquisition emerge only when both roots and mycorrhizal fungi are considered together.
Article
Full-text available
Ectomycorrhizal (ECM) fungi, symbiotic mutualists of many dominant tree and shrub species, exhibit a biogeographic pattern counter to the established latitudinal diversity gradient of most macroflora and fauna. However, an evolutionary basis for this pattern has not been explicitly tested in a diverse lineage. In this study, we reconstructed a mega-phylogeny of a cosmopolitan and hyper-diverse genus of ECM fungi, Russula, sampling from annotated collections and utilizing publically available sequences deposited in GenBank. Metadata from molecular operational taxonomic unit cluster sets were examined to infer the distribution and plant association of the genus. This allowed us to test for differences in patterns of diversification between tropical and extratropical taxa, as well as how their associations with different plant lineages may be a driver of diversification. Results show that Russula is most species-rich at temperate latitudes and ancestral state reconstruction shows that the genus initially diversified in temperate areas. Migration into and out of the tropics characterizes the early evolution of the genus, and these transitions have been frequent since this time. We propose the 'generalized diversification rate' hypothesis to explain the reversed latitudinal diversity gradient pattern in Russula as we detect a higher net diversification rate in extratropical lineages. Patterns of diversification with plant associates support host switching and host expansion as driving diversification, with a higher diversification rate in lineages associated with Pinaceae and frequent transitions to association with angiosperms. This article is protected by copyright. All rights reserved.
Article
Full-text available
The mutualistic association of roots with ectomycorrhizal fungi promotes plant health and is a hallmark of boreal and temperate forests worldwide. In the pre-colonization phase, before direct contact, lateral root (LR) production is massively stimulated, yet little is known about the signals exchanged during this step. Here, we identify sesquiterpenes (SQTs) as biologically active agents emitted by Laccaria bicolor while interacting with Populus or Arabidopsis. We show that inhibition of fungal SQT production by lovastatin strongly reduces LR proliferation and that (-)-thujopsene, a low-abundance SQT, is sufficient to stimulate LR formation in the absence of the fungus. Further, we show that the ectomycorrhizal ascomycote, Cenococcum geophilum, which cannot synthesize SQTs, does not promote LRs. We propose that the LR-promoting SQT signal creates a win-win situation by enhancing the root surface area for plant nutrient uptake and by improving fungal access to plant-derived carbon via root exudates.
Article
Full-text available
To elucidate the genetic bases of mycorrhizal lifestyle evolution, we sequenced new fungal genomes, including 13 ectomycorrhizal (ECM), orchid (ORM) and ericoid (ERM) species, and five saprotrophs, which we analyzed along with other fungal genomes. Ectomycorrhizal fungi have a reduced complement of genes encoding plant cell wall–degrading enzymes (PCWDEs), as compared to their ancestral wood decayers. Nevertheless, they have retained a unique array of PCWDEs, thus suggesting that they possess diverse abilities to decompose lignocellulose. Similar functional categories of nonorthologous genes are induced in symbiosis. Of induced genes, 7–38% are orphan genes, including genes that encode secreted effector-like proteins. Convergent evolution of the mycorrhizal habit in fungi occurred via the repeated evolution of a ‘symbiosis toolkit’, with reduced numbers of PCWDEs and lineage-specific suites of mycorrhiza-induced genes.
Article
Full-text available
Twenty-eight cultures of ectomycorrhizal fungi isolated from diverse host and habitat associations were tested in pure culture syntheses with the ericaceous hosts Arbutus menziesii Pursh and Arctostaphylos uva-ursi (L.) Spreng. All but three of the fungi formed arbutoid mycorrhizas. Sheathing fungal mantles, Hartig net penetration and intracellular colonization were well developed on most mycorrhizas. These results confirm that ectomycorrhizal fungi form arbutoid mycorrhizas and that these particular hosts are broadly receptive towards fungal associates. The significance of these results with respect to ecological and practical implications and better understanding of ectomycorrhizal specificity is emphasized. Arbutoid mycorrhizas are most closely related to ectomycorrhizas than to ericoid mycorrhizas.
Article
Full-text available
Disturbance can both initiate and shape patterns of secondary succession by affecting processes of community assembly. Thus, understanding assembly rules is a key element of predicting ecological responses to changing disturbance regimes. We measured the composition and trait characteristics of plant communities early after widespread wildfires in Alaska to assess how variations in disturbance characteristics influenced the relative success of different plant regeneration strategies. We compared patterns of post-fire community composition and abundance of regeneration traits across a range of fire severities within a single pre-fire forest type- black spruce forests of Interior Alaska. Patterns of community composition, as captured by multivariate ordination with nonmetric multidimensional scaling, were primarily related to gradients in fire severity (biomass combustion and residual vegetation) and secondarily to gradients in soil pH and regional climate. This pattern was apparent in both the full dataset (n = 87 sites) and for a reduced subset of sites (n = 49) that minimized the correlation between site moisture and fire severity. Changes in community composition across the fire-severity gradient in Alaska were strongly correlated to variations in plant regeneration strategy and rooting depth. The tight coupling of fire severity with regeneration traits and vegetation composition after fire supports the hypothesis that disturbance characteristics influence patterns of community assembly by affecting the relative success of different regeneration strategies. This study further demonstrated that variations in disturbance characteristics can dominate over environmental constraints in determining early patterns of community assembly. By affecting the success of regeneration traits, changes in fire regime directly shape the outcomes of community assembly, and thus may override the effects of slower environmental change on boreal forest composition.
Article
Full-text available
Climate changes have important consequences for plant communities and their root symbionts. The distribution of tree species within temperate, boreal and tropical biomes will be altered, as palaeoecological studies have demonstrated for previous climate change events. Predicted effects on ectomycorrhizal (ECM) associations include migration of host and symbiont, modification of interactions between plant and fungal species, and changes in the contribution of both partners to the global carbon cycle. Anthropogenic factors introduce new variables, affecting the ability of tree species and their fungal associates to disperse in response to climate change. Here we focus on how ECM fungi and their hosts respond to atmospheric CO2 enrichment, increasing temperatures, nutrient addition, species invasions, loss of biodiversity and anthropogenic land-use changes, particularly silviculture. All of these factors are key to understanding the impacts of climate change on the ECM symbiosis, and relevant future topics of research are presented.
Article
Full-text available
Recognition of the importance of land-use history and its legacies in most ecological systems has been a major factor driving the recent focus on human activity as a legitimate and essential subject of environmental science. Ecologists, conservationists, and natural resource policymakers now recognize that the legacies of land-use activities continue to influence ecosystem structure and function for decades or centuries - or even longer - after those activities have ceased. Consequently, recognition of these historical legacies adds explanatory power to our understanding of modern conditions at scales from organisms to the globe and reduces missteps in anticipating or managing for future conditions. As a result, environmental history emerges as an integral part of ecological science and conservation planning. By considering diverse ecological phenomena, ranging from biodiversity and biogeochemical cycles to ecosystem resilience to anthropogenic stress, and by examining terrestrial and aquatic ecosystems in temperate to tropical biomes, this article demonstrates the ubiquity and importance of land-use legacies to environmental science and management.
Article
Full-text available
Non-native forest pathogens can cause dramatic and long-lasting changes to the composition of forests, and these changes may have cascading impacts on community interactions and ecosystem functioning. Phytophthora ramorum, the causal agent of the emergent forest disease sudden oak death (SOD), has a wide host range, but mortality is concentrated in a few dominant tree species of coastal forests in California and Oregon. We examined interactions between P. ramorum and its hosts in redwood and mixed evergreen forest types over an 80,000 ha area in the Big Sur ecoregion of central California, an area that constitutes the southernmost range of the pathogen and includes forest stands on the advancing front of pathogen invasion. We established a network of 280 long-term forest monitoring plots to understand how host composition and forest structure facilitated pathogen invasion, and whether selective mortality from SOD has led to shifts in community composition. Infested and uninfested sites differed significantly in host composition due to both historical trends and disease impacts. A reconstruction of pre-disease forest composition showed that stands that eventually became infested with the pathogen tended to be more mature with larger stems than stands that remained pathogen-free, supporting the hypothesis of aerial dispersal by the pathogen across the landscape followed by local understory spread. The change in species composition in uninfested areas was minimal over the study period, while infested stands had large changes in composition, correlated with the loss of tanoak (Notholithocarpus densiflorus), signaling the potential for SOD to dramatically change coastal forests through selective removal of a dominant host. Forest diversity plays an important role in pathogen establishment and spread, and is in turn changed by pathogen impacts. Asymmetric competency among host species means that impacts of P. ramorum on forest diversity are shaped by the combination and dominance of hosts present in a stand.
Article
Full-text available
Majority of autotrophic plants and fungi associate with multiple mycorrhizal partners, with notable exceptions being Gnetum africanum, Pisonia grandis, and Alnus spp from the phytobiont perspective. We hypothesized that an understorey tree species Gnetum gnemon hosts a narrow range of mycobionts as shown in G. africanum and suggested for South American species. Sampling and molecular analysis of G. gnemon root tips revealed that besides Scleroderma spp. this gymnosperm tree associates with several fungal species from unrelated lineages. However, all Scleroderma isolates that associate with Gnetum spp. belong to a narrow clade close to Scleroderma sinnamariense. Our results demonstrate for the first time that specificity for mycobionts may substantially differ within an ectomycorrhizal plant genus.
Article
Full-text available
Ectomycorrhiza formation by 11, geographically distinct Eucalyptus species and Pinus radiata with 23 diverse ectomycorrhizal fungi was examined in pure culture syntheses. Few differences occurred between the Eucalyptus species in their ability to form ectomycorrhizas with several fungi, thus indicating no evidence for host-fungus specificity within Eucalyptus. Pinus radiata and most Eucalyptus species formed ectomycorrhizas in common with several broad-host-ranging fungi. However, fungus species which are known to associate exclusively with members of the Pinaceae, e.g. Suillus and Rhizopogon species, did not form ectomycorrhizas with any Eucalyptus species and vice versa. Possible incompatibility between several host-fungus combinations was characterized by host accumulation of phenolic compounds in epidermal and cortical cells. These results are discussed relevant to better understanding degrees and processes of ectomycorrhiza host-fungus specificity and compatibility and to practical considerations in reforestation of exotic plantations.
Article
Internal transcribed spacer regions of the nuclear ribosomal repeat have been sequenced from 47 isolates belonging to 38 recognized species of Suillus sensu lato. The sequences have been analyzed for phylogenetic and taxonomic implications using parsimony as well as distance methods. Based on these data, the genera Boletinus and Fuscoboletinus, that are often recognized within Suillus sensu lato, are not monophyletic. Isolates of Suillus granulatus derived from either North America or Europe and Asia are polyphyletic and seem to represent at least two different species. Our data also suggest that within Suillus sensu lato, mycorrhizal associations with Larix are primitive and host changes to Pinus and Pseudotsuga seem to have occurred only once. Changes among host species of the same genus appear to be more frequent. Finally, the most primitive clade within Suillus sensu lato seems to be formed by organisms with a strongly boletinoid hymenophore.
Article
Fifty fungi have been demonstrated to form ectomycorrhizae in pure culture synthesis with western hemlock. More than a hundred additional fungi are reported to be probable mycorrhiza formers with various hemlock species. Few seem to be host specific to hemlock. We hypothesize that little selection pressure towards evolution of fungal-host specificity exists with hosts such as hemlock, which commonly become established in the understory of established stands of other species.
Article
Mycorrhizal synthesis was successful between Pinus resinosa and Suillus americanus, S. brevipes (two isolates), S. luteus, and S. neoalbidipes, and between Pinus strobus and Suillus americanus, S. brevipes (two isolates), S. granulatus, S. pictus, and S. punctipes. Mycorrhizae formed by all combinations were similar in that all had multiple dichotomous branches, hyphae and hyphal strands with microscopic, pigmented, surface incrustations surrounding the mycorrhizae and roots, and in the mantle organization. Mycorrhizae differed in the macroscopic color of the mantle and surrounding hyphae and hyphal strands, the amount of hyphal surface incrustation present, the organization of individual hyphae in the mantle layers, the width of the mantle, the presence of clamp connections, and the amount of radial elongation of cortical cells. Data on additional diagnostic characters must be collected and evaluated for value in the identification of mycobionts of field-collected mycorrhizae.
Article
Multiple ectomycorrhizal fungi (EMF) compete to colonise the roots of a host plant, but it is not known whether their success is under plant or fungal control, or a combination of both. We assessed whether plants control EMF colonisation by preferentially allocating more carbon to more beneficial partners in terms of nitrogen supply or if other factors drive competitive success. We combined stable isotope labelling and RNA-sequencing approaches to characterise nutrient exchange between the plant host Eucalyptus grandis and three Pisolithus isolates when growing alone and when competing either indirectly (with a physical barrier) or directly. Overall, we found that nitrogen provision to the plant does not explain the amount of carbon that an isolate receives nor the number of roots that it colonises. Differences in nutrient exchange among isolates were related to differences in expression of key fungal and plant nitrogen and carbon transporter genes. When given a choice of partners, the plant was able to limit colonisation by the least cooperative isolate. This was not explained by a reduction in allocated carbon. Instead, our results suggest that partner choice in EMF could operate through the upregulation of defence-related genes against those fungi providing fewer nutrients.
Book
The roots of most plants are colonized by symbiotic fungi to form mycorrhiza, which play a critical role in the capture of nutrients from the soil and therefore in plant nutrition. Mycorrhizal Symbiosis is recognized as the definitive work in this area. Since the last edition was published there have been major advances in the field, particularly in the area of molecular biology, and the new edition has been fully revised and updated to incorporate these exciting new developments. . Over 50% new material . Includes expanded color plate section . Covers all aspects of mycorrhiza . Presents new taxonomy . Discusses the impact of proteomics and genomics on research in this area.
Article
Suillus luteus (Boletales, Agaricomycetes) associates solely with Pinaceae species as an ectomycorrhizal symbiont in the Northern Hemisphere. Prunus speciosa (Rosaceae) and Cedrela odorata (Meliaceae) naturally harbor arbuscular mycorrhizal fungi. The present study documents that S. luteus establishes root endophyte symbioses in vitro with somatic Prunus speciosa; however, it does not penetrate root tissues of somatic Cedrela odorata. With P. speciosa, the hyphae of S. luteus were heavily entangled in the intercellular space, unlike the rather straight hyphae of Tricholoma matsutake (Agaricales, Agaricomycetes). With C. odorata, S. luteus colonized only the surface of the exodermis and exhibited dark-brown mycorrhiza-like morphology. Prunus speciosa associated with S. luteus grew significantly better than that without the fungus, but C. odorata did not show significant beneficial effects when growing with the fungus. The data indicate that apparent Pinaceae-specific ectomycorrhizal fungi associate with arbuscular mycorrhizal broad-leaved plants in vitro, although the physical characteristics of the interactions vary depending upon the plant and fungal species.
Article
Soil depth partitioning is thought to promote the diversity of ectomycorrhizal (EM) fungal communities, but little is known about whether it is controlled by abiotic or biotic factors.In three bioassay experiments, we tested the role of vertical soil heterogeneity in determining the distributions and competitive outcomes of the EM sister species Rhizopogon vinicolor and Rhizopogon vesiculosus. We planted Pseudotsuga menziesii seedlings into soils that were either a homogenized mix of upper and lower depths or vertically stratified combinations mimicking natural field conditions.We found that both species colonized the upper or lower soil depths in the absence of competition, suggesting that their distributions were not limited by abiotic edaphic factors. In competition within homogeneous soils, R. vesiculosus completely excluded colonization by R. vinicolor, but R. vinicolor was able to persist when soils were stratified. The amount of colonization by R. vinicolor in the stratified soils was also significantly correlated with the number of multilocus genotypes present.Taken together, our findings suggest that the differential vertical distributions of R. vinicolor and R. vesiculosus in natural settings are probably attributable to competition rather than edaphic specialization, but that soil heterogeneity may play a key role in promoting EM fungal diversity.
Article
Nearly all northeastern U.S. forests have been disturbed by wind, logging, fire, or agriculture over the past several centuries. These disturbances may have long-term impacts on forest carbon and nitrogen cycling, affecting forests' vulnerability to N saturation and their future capacity to store C. We evaluated the long-term (80-110 yr) effects of logging and fire on aboveground biomass, foliar N (%), soil C and N pools, net N mineralization and nitrification, and NO3- leaching in northern hardwood forests in the White Mountain National Forest, New Hampshire. Historical land-use maps were used to identify five areas each containing previously logged, burned, and relatively undisturbed (oldgrowth) forests. Aboveground biomass averaged 192 Mg/ha on the historically disturbed sites and 261 Mg/ha on the old-growth sites, and species dominance shifted from early-successional and mid-successional species (Betula papyrifera and Acer rubrum) to late-successional species (Fagus grandifolia and particularly A. saccharum). Forest floors in the old-growth stands had less organic matter and lower C:N ratios than those in historically burned or logged sites. Estimated net N mineralization did not vary by land-use history (113 kg·ha-1·yr-1); mean (± 1 SE) nitrification rates at old-growth sites (63 ± 4.3 kg·ha-1·yr-1) doubled those at burned (34 ± 4.4 kg·ha-1·yr-1) and logged (29±4.7 kg·ha-1-yr-1) sites. Across all plots, nitrification increased as forest floor C:N ratio decreased, and NO3- concentrations in streamwater increased with nitrification. These results indicate that forest N cycling is affected by century-old disturbances. The increased nitrification at the old-growth sites may have resulted from excess N accumulation relative to C accumulation in forest soils, due in part to low productivity of old-aged forests and chronic N deposition.
Article
Global analyses of interspecific interactions are rapidly increasing our understanding of patterns and processes at large scales. Understanding how biodiversity assembles and functions on a global scale will increasingly require analyses of complex interactions at different ecological and phylogenetic levels. We present an analysis of host-plant associations in the sap-sucking Psylloidea (?3,800 species) using the most comprehensive assemblage of host data for this group compiled from 66?% of published records. Psyllids are known for high levels of host specificity and host switching between related plants at local scales, but a global survey implicates historical processes that are not entirely consistent with those at local scales. In particular, saltationary host switching events appear to have been a key factor explaining the wide but patchy distribution of psyllid host-plants throughout the angiosperm phylogeny. Alternative explanations involving co-diversification with subsequent extinction seem implausible. At the seed plant family level, we compare associations for psyllids with those of their relatives the aphids, but, despite notable differences in biogeographic distributions, find few plant families (2%) that host only psyllids but not aphids, while a much larger percentage (31%) host aphids but not psyllids, and 43% of plant families distributed throughout the plant phylogeny host neither group.
Article
Like all obligately ectomycorrhizal plants, pines require ectomycorrhizal fungal symbionts to complete their life cycle. Pines introduced into regions far from their native range are typically incompatible with local ectomycorrhizal fungi, and, when they invade, coinvade with fungi from their native range. While the identities and distributions of coinvasive fungal symbionts of pine invasions are poorly known, communities that have been studied are notably depauperate. However, it is not yet clear whether any number of fungal coinvaders is able to support a Pinaceae invasion, or whether very depauperate communities are unable to invade. Here, we ask whether there is evidence for a minimum species richness of fungal symbionts necessary to support a pine/ectomycorrhizal fungus coinvasion. We sampled a Pinus contorta invasion front near Coyhaique, Chile, using molecular barcoding to identify ectomycorrhizal fungi. We report that the site has a total richness of four species, and that many invasive trees appear to be supported by only a single ectomycorrhizal fungus, Suillus luteus. We conclude that a single ectomycorrhizal (ECM) fungus can suffice to enable a pine invasion.
Article
An ultrastructural study was made of the interactions between Suillus grevillei (Klotzsch) Sing. and 11 species of ectomycorrhizal hosts in aseptic culture in the absence of glucose. No mycorrhizas were formed between S. grevillei and Betula pubescens Ehrh., Allocasuarina inophloia (F. Muell. & F. M. Bail.) L. Johnson, Picea sitchensis (Bong.) Carr., Picea abies (L.) Karst. Alnus glutinosa (L.) Gaertn. or Pinus nigra Arnold, although the fungus grew in the rhizosphere of some of these and in P. nigra it penetrated and killed adjacent epidermal cells. Mycorrhizas were formed with Larix kaempferi (Lamb.) Carr., Larix decidua Mill, Pinus sylvestris L. and Pseudotsuga menziesii (Mirb.) Franco. However, ultrastructural changes in the host-fungus interface of associations with the latter two hosts suggest that in both cases the symbionts were not entirely compatible. The role of phenolic compounds in ectomycorrhizal compatibility and specificity is discussed.
Article
Mycorrhizal synthesis was successful between Pinus resinosa and Suillus americanus, S. brevipes (two isolates), S. luteus, and S. neoalbidipes, and between Pinus strobus and Suillus americanus, S. brevipes (two isolates), S. granulatus, S. pictus, and S. punctipes. Mycorrhizae formed by all combinations were similar in that all had multiple dichotomous branches, hyphae and hyphal strands with microscopic, pigmented, surface incrustations surrounding the mycorrhizae and roots, and in the mantle organization. Mycorrhizae differed in the macroscopic color of the mantle and surrounding hyphae and hyphal strands, the amount of hyphal surface incrustation present, the organization of individual hyphae in the mantle layers, the width of the mantle, the presence of clamp connections, and the amount of radial elongation of cortical cells. Data on additional diagnostic characters must be collected and evaluated for value in the identification of mycobionts of field-collected mycorrhizae.
Article
AimIt has been proposed that co-invasion with ectomycorrhizal (EM) fungi is a common mechanism by which non-indigenous trees overcome symbiont limitation, yet virtually all prior evidence has come from a single plant family, the Pinaceae. We tested the co-invasion hypothesis by examining the EM fungal communities associated with a specialized host, Alnus glutinosa (black alder), and a generalist host, Salix fragilis (crack willow), in New Zealand, where both trees are invasive. We aimed to find out if these two hosts, which often co-occur on invaded riverbanks, (1) were forming novel EM fungal associations in New Zealand and (2) had potential to facilitate each other through shared EM fungi.LocationNew Zealand.Methods We collected root tip samples from both host plants at riparian sites on the North Island and South Island and used DNA sequence-based identification to characterize EM fungal communities.ResultsBoth trees relied upon exotic EM fungi from their indigenous ranges and did not associate with any known endemic New Zealand EM fungi. Alnus had highly similar communities on both islands, while the Salix communities were distinct. All EM fungi on South Island Alnus were also present on South Island Salix, while North Island Salix did not substantially share EM fungal associates with Alnus.Main conclusionsOverall, our study indicates that plant hosts with specialized and more generalist EM fungal communities can both successfully invade new habitats with non-indigenous EM fungi. While there may be some potential for facilitation between these two EM plants hosts via shared non-indigenous fungi, this outcome was context specific. Our findings suggest that the specificity of fungal mutualists is not a major barrier to the spread of invasive plants and cannot be taken as evidence an introduced plant will not become invasive.
Article
Brown oak (Quercus semecarpifolia, a.k.a. Kharsu, bji shing) is a biologically and economically important evergreen broadleaved tree that dominates moist temperate and lower-montane forests throughout the mid-elevation Himalaya. We demarcated two paired spatially explicit one-hectare plots in an experimentally harvested area and an unharvested old growth reserve of Q. semecarpifolia dominated forest in the Bhutan Himalaya. We compared the structure, species composition and diversity, and spatial relationships between the two plots. To test whether harvesting had been successful in establishing a new cohort of oak we compared regeneration in plots established in 1999, to data gathered over ten years after. Regeneration plots showed a paucity of Quercus regeneration in both stands. Logging did not reduce tree species richness; however, Shannon diversity, Simpson diversity, and evenness were all lower in the logged stand. We used univariate and bivariate Ripley’s-K functions to assess the spatial distribution of trees in both stands and test whether single tree felling had altered the spatial relationships among and between species. Understory species were clumped at scales >30 m in canopy gaps in the old-growth reserve, whereas distribution in the logged plot was more random. Relationships between species show similar patterns with more than 80% of species showing significant clumping at scales from 12 m to 30 m, while ∼70% of relationships in the logged plot showed complete spatial randomness. In the old-growth reserve several species showed significant dispersion away from canopy dominant oaks. Scarce regeneration and significant changes in spatial pattern development in the harvested stand suggest changes to current silvicultural practice are needed.
Article
Alnus trees associate with ectomycorrhizal (ECM) fungi and nitrogen-fixing Frankia bacteria and, although their ECM fungal communities are uncommonly host specific and species poor, it is unclear whether the functioning of Alnus ECM fungal symbionts differs from that of other ECM hosts. We used exoenzyme root tip assays and molecular identification to test whether ECM fungi on Alnus rubra differed in their ability to access organic phosphorus (P) and nitrogen (N) when compared with ECM fungi on the non-Frankia host Pseudotsuga menziesii. At the community level, potential acid phosphatase (AP) activity of ECM fungal root tips from A. rubra was significantly higher than that from P. menziesii, whereas potential leucine aminopeptidase (LA) activity was significantly lower for A. rubra root tips at one of the two sites. At the individual species level, there was no clear relationship between ECM fungal relative root tip abundance and relative AP or LA enzyme activities on either host. Our results are consistent with the hypothesis that ECM fungal communities associated with Alnus trees have enhanced organic P acquisition abilities relative to non-Frankia ECM hosts. This shift, in combination with the chemical conditions present in Alnus forest soils, may drive the atypical structure of Alnus ECM fungal communities.
Article
The term “legacy effect” has been used in ecology since the early 1990s by authors studying plant succession, invasive-plant impacts, herbivory impacts, ecosystem engineering, and human land-use impacts. Although there is some variability in usage, the term is normally used to describe impacts of a species on abiotic or biotic features of ecosystems that persist for a long time after the species has been extirpated or ceased activity and which have an effect on other species. For example, human agricultural activities may have a legacy effect on soil structure and vegetative communities that lasts for centuries and which alters current communities. The concept may be related to the idea of ecological inheritance in evolutionary biology but would refer only to a subset of the features of this concept. In particular, legacy effects could refer to those kinds of ecological inheritance where a physical or biological change in ecosystem state is caused by one species, where this change persists after the extirpation of the causal species and alters selection pressure of another species much later in time.
Article
summaryThe uptake and assimilation of 16N-labelled ammonium was followed in Pinus sylvestris L. plants infected with four different ectomycorrhizal fungi, Rhizopogon roseolus Fr. Suillus bovinus (Fr.) O. Kuntze, Pisolithus tinctorius (Fr.) Fr. and Paxillus involutus (Mich, ex Pers.) Cohen & Couch. Plants were grown in flat perspex observation chambers or in Petri dishes containing non-sterile peat; in each case the fungal mycelium growing from a host plant was allowed to cross a barrier and to colonize an area of peat from which roots had been excluded. Labelled ammonium was fed to the mycelium, and the shoot, root and mycelial tissues analysed for total and 15N-labelled free amino acid contents after a feeding period of 72 h. High proportions of 15N-labelled glutamate/glutamine, aspartate/asparagine, and alanine were found in the fungal mycelia of all species except Pax. involutus where labelled aspartate/asparagine was not found. Lower proportions of labelled serine, threonine, tyrosine, lysine, ornithine and arginine were also found in the mycelium. The degree of 15N enrichment declined throughout the transport pathway but between 5 and 50% of the amino acids were 15N-labelled in the plant shoots. In total, at least 2–3 % of the nitrogen supplied was assimilated as labelled amino acid during the 3 day feeding period, the largest amounts of labelling occurred in glutamic acid/gultamine and aspartic acid/asparagine.
Article
summaryPinus sylvestris L. and Larix eurolepis Henry seedlings were grown together in non–sterile laboratory microcosms containing functional mycelial networks of one of three different ectomyeorrhizal Fungi. The fungi used were Suillus bovinus (Fr.) O. Kuntze, and two Fungi which are commonly considered to be specific to Larix spp., Suillus grevillei (Klotzsch) Sing, and Boletirms cavipes (Opat.) Kalchbr. Patterns of mycorrhizal infection, transport of labelled assimilate and phosphorus uptake within the microcosms were studied in order to evaluate tine functional attributes of associations formed between P. sylvestris and the two‘larch specific’fungi. Fungal colonization of lateral roots and accumulation of labelled assimilate from adjacent plants fed with 14CO2 was significantly greater in the roots of Pinus plants when the ectomycorrhizal fungus was S. bovinu, and significantly greater in Larix roots when the fungus was V. grevillei or li. cavipes. Kctomycorrhizas formed between P. sylvestris and Ii, cavipes were fully functional in terms of transfer of labelled assimilate to the fungal mycelium. In mixed communities infected by B. caripes, myeclial uptake and translocation of 32P-labelled orthophosphate was significantly greater to Larix plants than to Pinus plants. Formation of sheathed lateral roots on the Pinus plants was low. There was some autoradiographic evidence of phosphorus translocation from mycorrhizal pine roots to stem and leaf tissue hut levels of activity in the shoots were low, indicating limited translocation across the host-fungus interface.
Article
Eleven species of mycorrhizal fungi, selected from stands of either Eucalyptus spp., Allocasuarina spp. or Pinus radiata D. Don were tested in an aseptic system for their abilities to initiate ectomycorrhiza with Allocasuarina littoralis (Salisb.) L. Johnson, Casuarina equisetifolia ssp. equiselifolia L. and C. cunninghamiana Miq. Elaphamyces sp., Hysterangium sp., Laccaria laccata (Scop ex Fr.) Bk. & Br., Pisolithus tinctorius (Pers.) Coker & Couch, Scleroderma sp. and Thelephora terrestris (Ehrh.) Fr. formed ectomycorrhizas on all three hosts. Amanita sp. formed ectomycorrhizas on A. littoralis and C. cunninghamiana but not on C. equisetifolia. Paxillus involutus (Batch ex Fr.) Fr. formed ectomycorrhizas on A. littoralis only. P. tinctorius also formed ectomycorrhizas with C. obesa Miq. Rhizapogon luteolus Fr. & Nord, Suillus granulatus (L. ex Fr.) Kuntze and S. piperatus (Bull ex Fr.) O. Kuntze colonized the rhizosphere of Casuarinaceae but did not form ectomycorrhizas. The comparative intensity of ectomycorrhizal infection by P. tinctorius and L. laccata was assessed on four host species. Infection intensity ranged from 13 to 70%, of laterals infected and decreased for both fungal species in the order: A. littoralis > Eucalyptus pilularis Smith > C. equisetifolia > C. cunninghamiana. An exogenous supply of glucose induced greater and sometimes earlier, ectomycorrhizal infection of A. littoralis, C. equisetifolia and C. cunninghamiana by P. tinctorius and L. laccata than that in the absence of glucose. The optimum glucose level for these fungi and hosts in this synthesis system was 750 μg glucose (g soil)−1.
Article
Cultures of 28 ectomycorrhizal fungi were tested in pure culture syntheses for mycorrhiza formation with red alder. Only 4 of the 28 fungi tested formed characteristic ectomycorrhizae: Alpova diplophloeus, Paxillus involutus, Aslraeus pteridis, and Scleroderma hypogaeum. These mycorrhizae are briefly described, and the specialization of alder mycorrhizae is discussed.
Article
Fifty fungi have been demonstrated to form ectomycorrhizae in pure culture synthesis with western hemlock. Over a hundred additional fungi are probable mycorrhiza formers with various hemlock species. Few seem to be host specific to hemlock. Little selection pressure towards evolution of fungal-host specificity exists with hosts such as hemlock, which commonly become established in the understory of established stands of other species. -from Authors
Article
Vegetative inoculum of the ectomycorrhizal fungus Suillus luteus was thoroughly mixed into fumigated nursery soil, and northern red oak seedlings of four families were evaluated one and two years after sowing for ectomycorrhizal development, growth, and nutrition. At the end of year one, treated seedlings were successfully inoculated with S. luteus, but the percentage varied significantly with family. Suillus luteus persisted on lateral roots two years following sowing. Two of four seedling families inoculated with S. luteus were significantly larger in size than control plants. These results suggest that the fungal symbiont S. luteus can be successfully introduced into nurseries and that early ectomycorrhizal development improves the growth of northern red oak seedlings.
Article
summaryTo test the effect of ectomycorrhizal fungi (EMF) on interactions between host plants, Pseudotsuga menziesii (Mirb.) Franco and Pinus ponderosa Dougl. ex. Laws., seedlings were grown in replacement series in pasteurized soil with (a) no EMF added, (A) two EMF species added - Rhizopogon vinicolor Smith (specific to Douglas-fir) and R. ochraceorubens Smith (specific to pine), and (c) tour EMF species added - the two Rhizopogon species plus two host generalists, Laccaria laccata (Scop, ex Fr.) Bk. & Br, and Hebeloma crustuliniforme (Bull.) Quel. A replacement series in unpasteurized forest soil also was included. Seedlings without added EMF were colonized by the greenhouse contaminant, Thelephora terrestris. Without added EMF (but with T. terrestris), the tree species mutually inhibited one another, producing Relative Yield Totals significantly < 1; with EMF added, mutual inhibition disappeared. With four EMF species added, Pseudotsuga menziesii seedlings were significantly larger in mixture than in monoculture, with no corresponding decrease in the size of Pinus ponderoso seedlings; this was due solely to seedlings with L. laccata, which apparently enhanced nitrogen (N) and phosphorus (P) uptake by Pseudotsuga menziesii at the expense of luxury consumption by Pinus ponderosa. Graphical analysis suggested that better growth of Pseudotosuga menziesii in mixture with EMF added was related to improved P nitrogen. Both N and P nutrition of Pinus ponderosa was better in mixture with two than no EMF species added; there was no clear nutrient effect with four EMF species added. Results indicate that EMF can reduce competition between plant species and perhaps increase overall community P uptake. However, patterns were specific to both EMF and tree species and were quite different in unpasteurized soils. Hence generalizations about the effects of EMF on plant-plant interactions must be made cautiously.
Article
The requirements for regenerating northern red oak can be hypothesized from an understanding of the species' ecological life-history characteristics along with a knowledge of past and present disturbance patterns. The abundance of oak in the eastern forest is closely related to past land use and extensive disturbances. Frequent fires and heavy cutting favored oak because of its sprouting ability, while fires reduced common competitors. Northern red oak is neither an aggressive colonizer that is characteristic of early successional species nor an enduring, shade-tolerant, slow-grower that is typical of late successional species. Its regeneration requires an edge environment; one that is more mesic than exposed, open sites, but less competitive than the deep shade of a forest understory. To regenerate northern red oak, foresters need to create these conditions. Numerous cutting studies, however, have shown that overstory manipulation (partial or complete removal) alone will not regenerate northern red oak. Intense competition can be expected on the mesic sites suitable for northern red oak, and this competition must be controlled when regenerating this species. For. Sci. 34(1):19-40.
Article
Container-grown Quercus robur, Q. velutina, and Q. alba seedlings were inoculated with vegetative mycelium of five isolates of Pisolithus tinctorius, three isolates of Suillus granulatus, and one each of Cenococcum geophilum, Thelephora terrestris, and Suillus luteus. Isolates of P. tinctorius, T. terrestris, and S. luteus were most consistent in colonization success within a tree species, whereas inoculation with S. granulatus resulted in relatively poor colonization. In general, shoot length, root and shoot dry weights, and leaf area of Quercus seedlings with abundant ectomycorrhizae were significantly greater than for seedlings with few ectomycorrhizae. Pisolithus tinctorius, S. luteus, and T. terrestris stimulated significant positive seedling growth responses in all three tree species. Successful inoculation with all eleven fungal isolates indicates the potential for artificial establishment of selected ectomycorrhizal fungi on container-grown Quercus seedlings. Forest Sci. 30:364-372.
Article
Host identity has been recognized as a key determinant of the structure of ectomycorrhizal (ECM) fungal communities, but the importance of neighboring ECM hosts is less well understood. To investigate the relative importance of host and neighborhood effects, we examined the ECM fungal communities associated with Alnus rhombifolia, a host of specific ECM fungi, and Betula occidentalis, a host of generalist ECM fungi. We hypothesized that the host-specific Alnus-associated ECM fungal community would not be susceptible to the influence of plant neighborhood, while the generalist Betula-associated community would. ECM fungal communities on both hosts were characterized using ITS sequences derived from conspecific and heterospecific host settings at a field site in western Idaho, USA and from a growth chamber bioassay. In the field study, the Betula neighborhood added minor constituents to the Alnus ECM fungal community, while in the bioassay, late planting of Betula generated strong priority effects that allowed the established Alnus neighborhood to control the structure of the Betula community. Our results indicate that while host identity acts as a primary filter on the composition and diversity of ECM fungal communities, proximity to a closely related host can mediate significant changes in community structure. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.
Article
Summary • Carbon sink strength differences are examined here between ectomycorrhizal fungi in interaction with additions of ammonium and apatite (a phosphorus- and calcium-containing mineral). • Pinus muricata associated with Paxillus involutus and four suilloid isolates ( Suillus pungens and members of three Rhizopogon section Amylopogon species groups) were used in microcosm nutrient addition experiments. • The associations differed in ectomycorrhizal biomass, mycelial growth rate, bio- mass and respiration. P. involutus produced the lowest biomass of ectomycorrhizal connections to P. muricata , but it consumed proportionally more carbon per connection and transferred more than twice as much ammonium to the host per unit mycorrhizal biomass. Paxillus also colonized the soil more rapidly and intensely than the other fungi, but its mycelial respiration was lowest. Ammonium and apatite addition resulted in a marked increase in respiration and mycelial biomass, respectively, by the suilloid fungi. • The high carbon cost of ammonium uptake is suggested as one explanation for reduced sporocarp production and mycelial growth by ectomycorrhizal fungi commonly found after high levels of nitrogen addition.
Article
The evolution and determinants of host specificity in Lamellodiscus species (Monogenea, Diplectanidae) were investigated. The 20 known Mediterranean species were studied, all parasites of fishes from the family Sparidae (Teleostei). An index of specificity, which takes into account the phylogenetic relationships of their fish host spe-cies, was defined. The link between specificity and its potential determinants was investigated in a phylogenetic context using the method of independent contrasts. Host specificity in Lamellodiscus species appeared to be highly constrained by phylogeny, but also linked to host size. Mapping specificity onto the parasite phylogenetic tree suggests that specialist species do not represent an evolutionary dead end, and that specialization is not a derived condition. It is hypothesized that the ability to be generalist or specialist in Lamellodiscus is controlled by intrinsic, phylogenetically-related characteristics, and that specialist species tend to use large hosts, which may be more predictable. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77 , 431 -443.