Lichen species across Alaska produce highly active and stable ice nucleators.

Forty years ago, lichens were identified as extraordinary biological ice nucleators (INs) that enable ice formation at temperatures close to 0°C. By employing INs, lichens thrive in freezing environments that surpass the physiological limits of other vegetation, thus making them the majority of vegetative biomass in northern ecosystems. Aerosolized lichen INs might further impact cloud glaciation and have the potential to alter atmospheric processes in a warming Arctic. Despite the ecological importance and formidable ice nucleation activities, the abundance, diversity, sources, and role of ice nucleation in lichens remain poorly understood. Here, we investigate the ice nucleation capabilities of lichens collected from various ecosystems across Alaska. We find ice-nucleating activity in lichen to be widespread, particularly in the coastal rainforest of Southeast Alaska. Across 29 investigated lichen, all species show ice nucleation temperatures above -15 °C and ~30% initiate freezing at temperatures above -6 °C. Concentration series of lichen ice nucleation assays in combination with statistical analysis reveal that the lichens contain two subpopulations of INs, similar to previous observations in bacteria. However, unlike the bacterial INs, the lichen INs appear as independent subpopulations resistant to freeze-thaw cycles and against temperature treatment. The ubiquity and high stability of the lichen INs suggest that they can impact local atmospheric processes and that ice nucleation activity is an essential trait for their survival in cold environments.

Fomitopsis mounceae and F. schrenkii-two new species from North America in the F. pinicola complex.

Two new species, Fomitopsis mounceae and F. schrenkii (Polyporales, Basidiomycota) in the F. pinicola species complex in North America, are described and illustrated. Previous molecular phylogenetic analyses identified three well-delimited lineages that represent F. mounceae and F. ochracea from Canada, the Appalachian Mountains, and the northern United States and F. schrenkii from western and southwestern regions of the United States. Fomitopsis pinicola sensu stricto is restricted to Eurasia and does not occur in North America. Morphological descriptions of basidiocarps and cultures for F. mounceae, F. schrenkii, and F. ochracea are presented. The three species are readily differentiated by nuc rDNA internal transcribed spacer (ITS1-5.8S-ITS2 = ITS) sequence, geographic distribution, and basidiospore size. Polyporus ponderosus H. Schrenk is an earlier illegitimate synonym of F. schrenkii. Both F. mounceae and F. schrenkii have a heterothallic multiallelic incompatibility system.

Phylogeny of Fomitopsis pinicola: a species complex.

Fungal species with a broad distribution may exhibit considerable genetic variation over their geographic ranges. Variation may develop among populations based on geographic isolation, lack of migration, and genetic drift, though this genetic variation may not always be evident when examining phenotypic characters. Fomitopsis pinicola is an abundant saprotrophic fungus found on decaying logs throughout temperate regions of the Northern Hemisphere. Phylogenetic studies have addressed the relationship of F. pinicola to other wood-rotting fungi, but pan-continental variation within F. pinicola has not been addressed using molecular data. While forms found growing on hardwood and softwood hosts exhibit variation in habit and appearance, it is unknown if these forms are genetically distinct. In this study, we generated DNA sequences of the nuc rDNA internal transcribed spacers (ITS), the TEF1 gene encoding translation elongation factor 1-α, and the RPB2 gene encoding the second largest subunit of RNA polymerase II for collections across all major geographic regions where this fungus occurs, with a primary focus on North America. We used Bayesian and maximum likelihood analyses and evaluated the gene trees within the species tree using coalescent methods to elucidate evolutionarily independent lineages. We find that F. pinicola sensu lato encompasses four well-supported, congruent clades: a European clade, southwestern US clade, and two sympatric northern North American clades. Each clade represents distinct species according to phylogenetic and population-genetic species concepts. Morphological data currently available for F. pinicola do not delimit these species, and three of the species are not specific to either hardwood or softwood trees. Originally described from Europe, F. pinicola appears to be restricted to Eurasia. Based on DNA data obtained from an isotype, one well-defined and widespread clade found only in North America represents the recently described Fomitopsis ochracea The remaining two North American clades represent previously undescribed species.

Phylogeny of Fomitopsis pinicola: a species complex.

Fungal species with a broad distribution may exhibit considerable genetic variation over their geographic ranges. Variation may develop among populations based on geographic isolation, lack of migration, and genetic drift, though this genetic variation may not always be evident when examining phenotypic characters. Fomitopsis pinicola is an abundant saprotrophic fungus found on decaying logs throughout temperate regions of the Northern Hemisphere. Phylogenetic studies have addressed the relationship of F. pinicola to other wood-rotting fungi, but pan-continental variation within F. pinicola has not been addressed using molecular data. While forms found growing on hardwood and softwood hosts exhibit variation in habit and appearance, it is unknown if these forms are genetically distinct. In this study, we generated DNA sequences of the nuc rDNA internal transcribed spacers (ITS), the TEF1 gene encoding translation elongation factor 1-α, and the RPB2 gene encoding the second largest subunit of RNA polymerase II for collections across all major geographic regions where this fungus occurs, with a primary focus on North America. We used Bayesian and maximum likelihood analyses and evaluated the gene trees within the species tree using coalescent methods to elucidate evolutionarily independent lineages. We find that F. pinicola sensu lato encompasses four well-supported, congruent clades: a European clade, southwestern US clade, and two sympatric northern North American clades. Each clade represents distinct species according to phylogenetic and population-genetic species concepts. Morphological data currently available for F. pinicola do not delimit these species, and three of the species are not specific to either hardwood or softwood trees. Originally described from Europe, F. pinicola appears to be restricted to Eurasia. Based on DNA data obtained from an isotype, one well-defined and widespread clade found only in North America represents the recently described Fomitopsis ochracea The remaining two North American clades represent previously undescribed species.

Frequent circumarctic and rare transequatorial dispersals in the lichenised agaric genus Lichenomphalia (Hygrophoraceae, Basidiomycota).

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.

Two new species of dictyostelid cellular slime molds from Alaska.

In sampling soils to survey dictyostelid cellular slime molds in Alaska we encountered two groups of isolates that have morphologies that differ from any previously described species within their group. We sequenced the nuclear small subunit ribosomal RNA gene (SSU rDNA) of selected isolates from the two groups and found sequences from both groups to be distinct from all previously described dictyostelid sequences. Phylogenetic analyses place one novel species in dictyostelid Group 2 and the other in Group 4 (Schaap et al. 2006). In this paper we formally describe as new these two species of cellular slime molds, Dictyostelium ammophilum sp. nov. and Dictyostelium boreale sp. nov., based on the combination of morphological and molecular characters.

Phylogenetic and ecological analyses of soil and sporocarp DNA sequences reveal high diversity and strong habitat partitioning in the boreal ectomycorrhizal genus Russula (Russulales; Basidiomycota).

SUMMARY: *Although critical for the functioning of ecosystems, fungi are poorly known in high-latitude regions. Here, we provide the first genetic diversity assessment of one of the most diverse and abundant ectomycorrhizal genera in Alaska: Russula. *We analyzed internal transcribed spacer rDNA sequences from sporocarps and soil samples using phylogenetic methods, operational taxonomic unit (OTU) delimitations and ordinations to compare species composition in various types of boreal forest. *The genus Russula is highly diverse in Alaska, with at least 42 nonsingleton OTUs (soil) and 50 phylogroups (soil + sporocarp). Russula taxa showed strong habitat preference to one of the two major forest types in the sampled regions (black spruce and birch-aspen-white spruce), and some preference for soil horizon. *Our results show that the vast majority of Russula species are present in the soil samples, although some additional taxa are expected to be found with extended sampling. OTU diversity in black spruce forests was only one-third of the diversity observed in mixed upland forests. Our findings suggest that some of the diversity is niche based, especially along host and successional axes, because most OTUs predictably occurred in specific habitats, regardless of geographical location.

Molecular phylogenetic biodiversity assessment of arctic and boreal ectomycorrhizal Lactarius Pers. (Russulales; Basidiomycota) in Alaska, based on soil and sporocarp DNA.

Despite the critical roles fungi play in the functioning of ecosystems, especially as symbionts of plants and recyclers of organic matter, their biodiversity is poorly known in high-latitude regions. In this paper, we discuss the molecular diversity of one of the most diverse and abundant groups of ectomycorrhizal fungi: the genus Lactarius Pers. We analysed internal transcribed spacer rDNA sequences from both curated sporocarp collections and soil polymerase chain reaction clone libraries sampled in the arctic tundra and boreal forests of Alaska. Our genetic diversity assessment, based on various phylogenetic methods and operational taxonomic unit (OTU) delimitations, suggests that the genus Lactarius is diverse in Alaska, with at least 43 putative phylogroups, and 24 and 38 distinct OTUs based on 95% and 97% internal transcribed spacer sequence similarity, respectively. Some OTUs were identified to known species, while others were novel, previously unsequenced groups. Non-asymptotic species accumulation curves, the disparity between observed and estimated richness, and the high number of singleton OTUs indicated that many Lactarius species remain to be found and identified in Alaska. Many Lactarius taxa show strong habitat preference to one of the three major vegetation types in the sampled regions (arctic tundra, black spruce forests, and mixed birch-aspen-white spruce forests), as supported by statistical tests of UniFrac distances and principal coordinates analyses (PCoA). Together, our data robustly demonstrate great diversity and nonrandom ecological partitioning in an important boreal ectomycorrhizal genus within a relatively small geographical region. The observed diversity of Lactarius was much higher in either type of boreal forest than in the arctic tundra, supporting the widely recognized pattern of decreasing species richness with increasing latitude.

Molecular diversity assessment of arctic and boreal Agaricus taxa.

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.

Evidence for strong inter- and intracontinental phylogeographic structure in Amanita muscaria, a wind-dispersed ectomycorrhizal basidiomycete.

A growing number of molecular studies show that many fungi have phylogeographic structures and that their distinct lineages are usually limited to different continents. As a conservative test of the extent to which wind-dispersed mycorrhizal fungi may exhibit phylogeographic structure, we chose to study Amanita muscaria, a host-generalist, widespread, wind-dispersed fungus. In this paper, we document the existence of several distinct phylogenetic species within A. muscaria, based on multilocus DNA sequence data. According to our findings, A. muscaria has strong intercontinental genetic disjunctions, and, more surprisingly, has strong intracontinental phylogeographic structure, particularly within North America, often corresponding to certain habitats and/or biogeographic provinces. Our results indicate that the view of A. muscaria as a common, widespread, easily identifiable, ecologically plastic fungus with a wide niche does not correctly represent the ecological and biological realities. On the contrary, the strong associations between phylogenetic species and different habitats support the developing picture of ecoregional endemisms and relatively narrow to very narrow niches for some lineages.