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Root‐associated fungi play a critical role in plant ecophysiology, growth and subsequent responses to disturbances, so they are thought to be particularly instrumental in shaping vegetation dynamics after fire in the boreal forest. Despite increasing data on the distribution of fungal taxonomic diversity through space and time in boreal ecosystems, there are knowledge gaps with respect to linking these patterns to ecosystem function and process.Here we explore what is currently known about postfire root‐associated fungi in the boreal forest. We focus on wildfire impacts on mycorrhizal fungi and the relationships between plant–fungal interactions and forest recovery in an effort to explore whether postfire mycorrhizal dynamics underlie plant–soil feedbacks that may influence fire‐facilitated vegetation shifts.We characterize the mechanisms by which wildfire influences root‐associated fungal community assembly. We identify scenarios of postfire plant–fungal interactions that represent putative positive and negative plant–soil feedbacks that may impact successional trajectories. We highlight the need for empirical field observations and experiments to inform our ability to translate patterns of postfire root‐associated fungal diversity to ecological function and application in models.We suggest that understanding postfire interactions between root‐associated fungi and plants is critical to predict fire effects on vegetation patterns, ecosystem function, future landscape flammability and feedbacks to climate. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

The occurrence and magnitude of natural fossil methane (CH4) emissions in the Arctic are poorly known. Emission of geologic CH4, a potent greenhouse gas, originating beneath permafrost is of particular interest due to the potential for positive feedback to climate warming, whereby accelerated permafrost thaw releases permafrost‐trapped CH4 in a future warmer climate. The development of through‐going taliks in Arctic lakes overlying hydrocarbon reservoirs is one mechanism of releasing geologically sourced, subpermafrost CH4. Here we use novel gas flux measurements, geophysical observations of the subsurface, shallow sediment coring, high‐resolution bathymetry measurements, and lake water chemistry measurements to produce a synoptic survey of the gas vent system in Esieh Lake, a northwest Alaska lake with exceedingly large geologic CH4 seep emissions. We find that microbially produced fossil CH4 is being vented though a narrow thaw conduit below Esieh Lake through pockmarks on the lake bottom. This is one of the highest flux geologic CH4 seep fields known in the terrestrial environment and potentially the highest flux single methane seep. The poleward retreat of continuous permafrost may have implications for more subcap CH4 release with increased permafrost thaw. [ABSTRACT FROM AUTHOR]

Fungi are abundant and functionally important in the Arctic, yet comprehensive studies of their diversity in relation to geography and environment are not available. We sampled soils in paired plots along the North American Arctic Transect ( NAAT), which spans all five bioclimatic subzones of the Arctic. Each pair of plots contrasted relatively bare, cryoturbated patterned-ground features ( PGFs) and adjacent vegetated between patterned-ground features (b PGFs). Fungal communities were analysed via sequencing of 7834 ITS- LSU clones. We recorded 1834 OTUs - nearly half the fungal richness previously reported for the entire Arctic. These OTUs spanned eight phyla, 24 classes, 75 orders and 120 families, but were dominated by Ascomycota, with one-fifth belonging to lichens. Species richness did not decline with increasing latitude, although there was a decline in mycorrhizal taxa that was offset by an increase in lichen taxa. The dominant OTUs were widespread even beyond the Arctic, demonstrating no dispersal limitation. Yet fungal communities were distinct in each subzone and were correlated with soil p H, climate and vegetation. Communities in subzone E were distinct from the other subzones, but similar to those of the boreal forest. Fungal communities on disturbed PGFs differed significantly from those of paired stable areas in b PGFs. Indicator species for PGFs included lichens and saprotrophic fungi, while bPGFs were characterized by ectomycorrhizal and pathogenic fungi. Our results suggest that the Arctic does not host a unique mycoflora, while Arctic fungi are highly sensitive to climate and vegetation, with potential to migrate rapidly as global change unfolds. [ABSTRACT FROM AUTHOR]

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Abstract: Fungi are ubiquitous in Arctic soils, where they function as symbionts and decomposers and may affect the carbon balance of terrestrial ecosystems subjected to climate change, and yet little is known about soil fungi at high latitudes. Here we review data from recent molecular studies to determine broad patterns in Arctic soil fungal ecology. The data indicate comparatively high fungal diversity in Arctic soils, with currently no evidence for lower species richness at higher latitudes. The dominant fungi, and particularly ectomycorrhizal-forming fungi, appear to be cosmopolitan species. Arctic soil fungi are capable of growth at sub-zero temperatures, melanized forms are frequent, host specificity is low and there is evidence that community composition alters under experimental warming. Future challenges are to determine the drivers of fungal diversity, whether or not diversity alters at higher latitudes and how apparently cosmopolitan fungi are able to survive the extreme environments encountered in Arctic habitats. [Copyright &y& Elsevier]

Aim Current evidence from temperate studies suggests that ectomycorrhizal (ECM) fungi require overland routes for migration because of their obligate symbiotic associations with woody plants. Despite their key roles in arctic ecosystems, the phylogenetic diversity and phylogeography of arctic ECM fungi remains little known. Here we assess the phylogenetic diversity of ECM communities in an isolated, formerly glaciated, high arctic archipelago, and provide explanations for their phylogeographic origins. Location Svalbard. Methods We generated and analysed internal transcribed spacer (ITS) nuclear ribosomal DNA sequences from both curated sporocarp collections (from Svalbard) and soil polymerase chain reaction (PCR) clone libraries (from Svalbard and the North American Arctic), compared these with publicly available sequences in GenBank, and estimated the phylogenetic diversity of ECM fungi in Svalbard. In addition, we conducted coalescent analyses to estimate migration rates in selected species. Results Despite Svalbard's geographic isolation and arctic climate, its ECM fungi are surprisingly diverse, with at least 72 non-singleton operational taxonomic units (soil) and 109 phylogroups (soil + sporocarp). The most species-rich genera are Thelephora/ Tomentella, Cortinarius and Inocybe, followed by Hebeloma, Russula, Lactarius, Entoloma, Sebacina, Clavulina, Laccaria, Leccinum and Alnicola. Despite the scarcity of available reference data from other arctic regions, the majority of the phylogroups (73.4%) were also found outside Svalbard. At the same time, all putative Svalbard 'endemics' were newly sequenced taxa from diverse genera with massive undocumented diversity. Overall, our results support long-distance dispersal more strongly than vicariance and glacial survival. However, because of the high variation in nucleotide substitution rates among fungi, allopatric persistence since the Pliocene, although unlikely, cannot be statistically rejected. Results from the coalescent analyses suggest recent gene flow among different arctic areas. Main conclusions Our results indicate numerous recent colonization events and suggest that long-distance, transoceanic dispersal is widespread in arctic ECM fungi, which differs markedly from the currently prevailing view on the dispersal capabilities of ECM fungi. Our molecular evidence indicates that long-distance dispersal has probably played a major role in the phylogeographic history of some ECM fungi in the Northern Hemisphere. Our results may have implications for studies on the biodiversity, ecology and conservation of arctic fungi in general. [ABSTRACT FROM AUTHOR]

Aim We examined genetic structure and long-distance gene flow in two lichenized ascomycetes, Flavocetraria cucullata and Flavocetraria nivalis, which are widespread in arctic and alpine tundra. Location Circumpolar North. Methods DNA sequences were obtained for 90 specimens (49 for F. cucullata and 41 for F. nivalis) collected from various locations in Europe, Asia and North America. Sequences of the nuclear internal transcribed spacer (ITS) + 5.8S ribosomal subunit gene region were generated for 89 samples, and supplemented by beta-tubulin (BTUB) and translation elongation factor 1-alpha gene (EF1) sequences for a subset of F. cucullata specimens. Phylogenetic, nonparametric permutation methods and coalescent analyses were used to assess population divergence and to estimate the extent and direction of migration among continents. Results Both F. cucullata and F. nivalis were monophyletic, supporting their morphology-based delimitation, and had high and moderately high intraspecific genetic diversity, respectively. Clades within each species contained specimens from both North America and Eurasia. We found only weak genetic differentiation among North American and Eurasian populations, and evidence for moderate to high transoceanic gene flow. Main conclusions Our results suggest that both F. cucullata and F. nivalis have been able to migrate over large distances in response to climatic fluctuations. The high genetic diversity observed in the Arctic indicates long-term survival at high latitudes, whereas the estimated migration rates and weak geographic population structure suggest a continuing long-distance gene flow between continents that has prevented pronounced genetic differentiation. The mode of long-distance dispersal is unknown, but wind dispersal of conidia and/or ascospores is probably important in the open arctic landscapes. The high genetic diversity and efficient long-distance dispersal capability of F. cucullata and F. nivalis suggest that these species, and perhaps other arctic lichens as well, will be able to track their potential niche in the changing Arctic. [ABSTRACT FROM AUTHOR]

As Arctic soils warm, thawed permafrost releases nitrogen (N) that could stimulate plant productivity and thus offset soil carbon losses from tundra ecosystems. Although mycorrhizal fungi could facilitate plant access to permafrost-derived N, their exploration capacity beyond host plant root systems into deep, cold active layer soils adjacent to the permafrost table is unknown. We characterized root-associated fungi (RAF) that colonized ericoid (ERM) and ectomycorrhizal (ECM) shrub roots and occurred below the maximum rooting depth in permafrost thaw-front soil in tussock and shrub tundra communities. We explored the relationships between root and thaw front fungal composition and plant uptake of a 15 N tracer applied at the permafrost boundary. We show that ERM and ECM shrubs associate with RAF at the thaw front providing evidence for potential mycelial connectivity between roots and the permafrost boundary. Among shrubs and tundra communities, RAF connectivity to the thaw boundary was ubiquitous. The occurrence of particular RAF in both roots and thaw front soil was positively correlated with 15 N recovered in shrub biomass Taxon-specific RAF associations could be a mechanism for the vertical redistribution of deep, permafrost-derived nutrients, which may alleviate N limitation and stimulate productivity in warming tundra., (© 2019 The Authors. New Phytologist © 2019 New Phytologist Trust.)

Species of the genus Lichenomphalia are mostly restricted to arctic-alpine environments with the exception of Lichenomphalia umbellifera which is also common in northern forests. Although Lichenomphalia species inhabit vast regions in several continents, no information is available on their genetic variation across geographic regions and the underlying population-phylogenetic patterns. We collected samples from arctic and subarctic regions, as well as from newly discovered subantarctic localities for the genus. Phylogenetic, nonparametric permutation methods, and coalescent analyses were used to assess phylogeny and population divergence and to estimate the extent and direction of gene flow among distinct geographic populations. All known species formed monophyletic groups, supporting their morphology-based delimitation. In addition, we found two subantarctic phylogenetic species (Lichenomphalia sp. and Lichenomphalia aff. umbellifera), of which the latter formed a well-supported sister group to L. umbellifera. We found no significant genetic differentiation among conspecific North American and Eurasian populations in Lichenomphalia. We detected high intercontinental gene flow within the northern polar region, suggesting rapid (re)colonisation of suitable habitats in response to climatic fluctuations and preventing pronounced genetic differentiation. On the other hand, our phylogenetic analyses suggest that dispersal between northern circumpolar and subantarctic areas likely happened very rarely and led to the establishment and subsequent divergence of lineages. Due to limited sampling in the Southern Hemisphere, it is currently uncertain whether the northern lineages occur in Gondwanan regions. On the other hand, our results strongly suggest that the southern lineages do not occur in the circumpolar north. Although rare transequatorial dispersal and subsequent isolation may explain the emergence of at least two subantarctic phylogenetic species lineages in Lichenomphalia, more samples from the Southern Hemisphere are needed to better understand the phylogeographic history of the genus., (Copyright © 2011 The British Mycological Society. All rights reserved.)

We provide a phylogenetic diversity assessment study in genus Agaricus as part of our ongoing work to saturate ITS and LSU rDNA sequence diversity of soil-dwelling fungi in Alaska. Pairwise sequence similarity-based groupings and statistical parsimony analyses were applied to delimit operational taxonomic unit (OTU) and were compared to results of full phylogenetic analyses. Our results show that the proportion of section Arvenses taxa is particularly high in the boreal forest and hypo-arctic (low arctic) regions, whereas the genus is represented by section Agaricus in high arctic habitats. Furthermore our findings suggest that the commercially important A. bisporus occurs naturally in the boreal region of interior Alaska, substantially expanding the known northern limit of the species. Delimitations of OTU varied greatly with different methods. In general 95% similarity-based grouping proved to be the least sensitive method, often resulting in section- and subsection-level groups. The 95% connection-limit statistical parsimony separated far more groups. The 98% similarity-based groups and the 98% connection limit networks recognized respectively 11 and 13 OTU containing our specimens. The 98% connection limit statistical parsimony was the only method in which all recognized OTU consisted of members grouped by branches with significant (> .95) posterior probabilities, providing an independent support for the groups. Our results also point out that considerable additional efforts will be needed to elucidate the evolution of this diverse genus and to assess its phylogenetic diversity, given that most taxa in our analyses could not be placed convincingly within well characterized species using ITS/LSU data.

Zooplankton of the family Bosminidae have a unique paleolimnological record in many Holarctic lakes that provides a near continuous record of morphological change for thousands of years. If this morphological change could be interpreted reliably, then a rarely achieved direct observation of macroevolution would be feasible. We tested paleolimnological predictions derived from morphological variation found in the genus Eubosmina using mtDNA and nuclear DNA sequence variation from geographically distant Holarctic sites. The mtDNA and nDNA trees were congruent but genetic divergence was inversely associated with morphological divergence. The three most genetically divergent groups belonged to Eubosmina longispina, whose phylogeography and genetic divergence was consistent with glacial vicariance. The genetic evidence also supported the hypothesis that at least two Nearctic species were recent European introductions. Finally, the genetic evidence was consistent with paleolimnology in the finding of several proposed species undergoing rapid morphological evolution and being post-glacially derived from European E. longispina. The results suggested that lacustrine bosminids are susceptible to geographic speciation processes, and that morphological interpretation of diversity in paleolimnology can be markedly improved by genetic studies.