Seasonal dynamics of ectomycorrhizal fungus assemblages on oak seedlings in the southeastern Appalachian Mountains.

The potential for seasonal dynamics in ectomycorrhizal (EM) fungal assemblages has important implications for the ecology of both the host trees and the fungal associates. We compared EM fungus distributions on root systems of out-planted oak seedlings at two sites in mixed southeastern Appalachian Mountain forests at the Coweeta Hydrologic Laboratory in North Carolina, from samples taken in mid-July and early September. Species level EM fungus type specificity, and identification in some cases, was enabled by direct sequencing of the mycobionts from the seedling roots. Seventy-four EM fungal ITS types were documented, most of which occurred only in the midsummer or early-fall samples, respectively. Cenococcum geophilum (morphotyped) was ubiquitously present and accounted for the majority of root tips sampled. Abundance and relative frequency of types other than C. geophilum were significantly higher in the July samples, while C. geophilum was significantly more frequent and abundant in September. Several generalistic dominants were found fairly equally at both sites and on both sample dates. Other taxa with relatively high frequency were recovered from both sites and tree seedling species, but were reliable indicators occurring primarily in the July sample (e.g., Laccaria cf laccata). Notable shifts in mycobiont dominance were apparent in relation to sample date, including increases in Cortinarius spp. richness, decreases in Thelephoraceae richness, and the disappearance of Amanita spp. types in the early fall compared to midsummer samples. However, diversity and rarity were high and differences in overall community composition (other than C. geophilum) by season were not significant based on multi-response permutation procedures. Although these results based on a single growing season are preliminary, changes in abundance and frequency, detection of significant indicator species, and the apparent systematic affinities of shifting EM types support the potential for seasonal variability in EM associations in this system.

The mycorrhizal status of Pseudotulostoma volvata (Elaphomycetaceae, Eurotiales, Ascomycota).

Pseudotulostoma volvata (O. K. Mill. and T. W. Henkel) is a morphologically unusual member of the otherwise hypogeous Elaphomycetaceae due to its epigeous habit and exposed gleba borne on an elevated stalk at maturity. Field observations in Guyana indicated that P. volvata was restricted to rain forests dominated by ectomycorrhizal (EM) Dicymbe corymbosa (Caesalpiniaceae), suggesting an EM nutritional mode for the fungus. In this paper, we confirm the EM status of P. volvata with a combination of morphological, molecular, and mycosociological data. The EM status for P. volvata corroborates its placement in the ectotrophic Elaphomycetaceae.

Hyperdiversity of ectomycorrhizal fungus assemblages on oak seedlings in mixed forests in the southern Appalachian Mountains.

Diversity of ectotrophic mycobionts on outplanted seedlings of two oak species (Quercus rubra and Quercus prinus) was estimated at two sites in mature mixed forests in the southern Appalachian Mountains by sequencing nuclear 5.8S rRNA genes and the flanking internal transcribed spacer regions I and II (ITS). The seedlings captured a high diversity of mycorrhizal ITS-types and late-stage fungi were well represented. Total richness was 75 types, with 42 types having a frequency of only one. The first and second order jackknife estimates were 116 and 143 types, respectively. Among Basidiomycetes, tomentelloid/thelephoroid, russuloid, and cortinarioid groups were the richest. The ascomycete Cenococcum geophilum was ubiquitously present. Dominant fungi included a putative Tuber sp. (Ascomycetes), and Basidiomycetes including a putative Craterellus sp., and Laccaria cf. laccata. Diversity was lower at a drier high elevation oak forest site compared to a low elevation mesic cove--hardwood forest site. Fungal specificity for red oak vs. white oak seedlings was unresolved. The high degree of rarity in this system imposes limitations on the power of community analyses at finer scales. The high mycobiont diversity highlights the potential for seedlings to acquire carbon from mycelial networks and confirms the utility of using outplanted seedlings to estimate ectomycorrhizal diversity.

A new subspecies of Mycenastrum corium from colorado.

During field work in Colorado an unusual form of Mycenastrum corium with a deep rusty red to reddish orange gleba was found. The species exists worldwide and lacks a previous description of the gleba at maturity other than olive brown, brown to purple brown. A subspecies is proposed for this unusual population found in an area where normal populations with the typical glebal color are found.

The Crepidotaceae (Basidiomycota, Agaricales): phylogeny and taxonomy of the genera and revision of the family based on molecular evidence.

Advances in phylogenetic systematics have clarified the position of most major homobasidiomycete lineages. In contrast, the status of the Crepidotaceae, a historically controversial family of dark-spored agarics, remains unaddressed. In this paper, current morphology-based classifications of the agaric genera of the Crepidotaceae were evaluated by parsimony and constraint analyses of sequence data from the nuclear large subunit rDNA. Taxa analyzed included the type species for each agaric genus allied in the family by Singer: Crepidotus, Simocybe, Pleurotellus, Tubaria, and Melanomphalia. Contrary to traditional classifications, results suggest that the crepidotoid fungi have three separate origins within the euagarics. The Crepidotaceae sensu stricto (s.s.) includes Crepidotus and Simocybe and represents a separate lineage of dark-spored euagarics. Pleurotellus is congeneric with Crepidotus. Results indicate the exclusion of both Tubaria and Melanomphalia from the Crepidotaceae s.s. Tubaria is allied with the strophariaceous taxa Phaeomarasmius and Flammulaster, while Melanomphalia has arisen from within a lineage of light-spored omphalinoid euagarics representing an independent acquisition of basidiospore pigmentation. Other pleisiomorphic and newly uncovered synapomorphic characters are discussed in detail along with the taxonomic status of each genus, and a revised family description is provided.

Scleroderma stellatum versus Scleroderma bermudense: the status of Scleroderma echinatum and the first record of Veligaster nitidum from the Virgin Islands.

The type of Scleroderma stellatum from Brazil exhibits a sharp echinulate, dark brown peridium, and the type of S. bermudense from Bermuda has a peridium that is loosely woven and fibrillose, whitish to pale brownish. These characters indicate two independent species. This information is contrary to that of Guzmán in 1970, who interpreted S. bermudense to be a synonym of S. stellatum based on the similar spores. Scleroderma echinatum from Borneo and Panama, as recently discussed by Guzmán and Ovrebo, also has an echinulate, dark brown peridium and is a synonym of S. stellatum. All these fungi have a stellate dehiscence. New records of S. bermudense from the Greater Antilles and Mexico's Pacific Coast, and Veligaster nitidum from Virgin Islands also are discussed.

The Gomphidiaceae revisited: a worldwide perspective.

Recent studies in the Gomphidiaceae have clearly delimited two genera, Gomphidius and Chroogomphus, both of which are mycorrhizal associates only with the Pinaceae. Ecological studies show Chroogomphus as a mycorrhizal associate of Pinus (Pinoideae), while Gomphidius is associated with the other three gymnosperm subfamilies Piceoideae, Lariceideae, and Abietoideae. The genus Brauniellula, which is based upon the secotioid habit and the presence of orthotropic, statismosporic basidia, falls within Chroogomphus in a clade with ballistosporic species. Brauniellula is, therefore, placed in synonymy with Chroogomphus. Molecular and morphological studies of new material from Nepal, Russia, Korea, and the United States have delimited two new species in each genus. The morphologically identical Chroogomphus rutilus clades are separate, one European and one North American. The relationship of the two genera in the Gomphidiaceae, with their mycorrhizal associates, is related to similar host relationships within other genera in the Suilloid Clade.

One hundred and seventeen clades of euagarics.

This study provides a first broad systematic treatment of the euagarics as they have recently emerged in phylogenetic systematics. The sample consists of 877 homobasidiomycete taxa and includes approximately one tenth (ca. 700 species) of the known number of species of gilled mushrooms that were traditionally classified in the order Agaricales. About 1000 nucleotide sequences at the 5(') end of the nuclear large ribosomal subunit gene (nLSU) were produced for each taxon. Phylogenetic analyses of nucleotide sequence data employed unequally weighted parsimony and bootstrap methods. Clades revealed by the analyses support the recognition of eight major groups of homobasidiomycetes that cut across traditional lines of classification, in agreement with other recent phylogenetic studies. Gilled fungi comprise the majority of species in the euagarics clade. However, the recognition of a monophyletic euagarics results in the exclusion from the clade of several groups of gilled fungi that have been traditionally classified in the Agaricales and necessitates the inclusion of several clavaroid, poroid, secotioid, gasteroid, and reduced forms that were traditionally classified in other basidiomycete orders. A total of 117 monophyletic groups (clades) of euagarics can be recognized on the basis on nLSU phylogeny. Though many clades correspond to traditional taxonomic groups, many do not. Newly discovered phylogenetic affinities include for instance relationships of the true puffballs (Lycoperdales) with Agaricaceae, of Panellus and the poroid fungi Dictyopanus and Favolaschia with Mycena, and of the reduced fungus Caripia with Gymnopus. Several clades are best supported by ecological, biochemical, or trophic habits rather than by morphological similarities.

Ectomycorrhizal sporophore distributions in a southeastern Appalachian mixed hardwood/conifer forest with thickets of Rhododendron maximum.

Sporophore abundance of putatively ectomycorrhizal fungi was compared in a mature mixed hardwood/conifer forest inside of (+) versus outside of (-) Rhododendron maximum thickets (RmT). Experimental blocks (1/4 ha) were established inside of (3) and outside of (3) RmT at the Coweeta Hydrologic Laboratory in Macon County, North Carolina, USA. Litter and organic layer substrates were removed, composited and redistributed among 90 2 × 2m plots within the blocks. Plots received either +RmT or -RmT litter, and either +RmT or -RmT organic layers, or were unmanipulated for controls. Sporophores of 67 putatively ectomycorrhizal species were collected from the blocks. Species diversity and overall community structure were similar inside of and outside of RmTs, and no grouping was detected by substrate type. Differences within the ectomycorrhizal fungus community were associated only weakly with environmental parameters, as indicated by ordination. In light of these results, recent observations of ectomycorrhizal suppression and strong shifts in the proportions of morphotypes on tree seedlings inside of RmT do not appear to be related to differences in sporophore distributions. The changes in seedling mycobiont dominance in relation to RmT and the influence this has on seedling health should be examined directly from root tips.

Two new species of Gomphidius from the Western United States and Eastern Siberia.

Study of the genus Gomphidius from recent material from Asia and North America has been carried out using traditional taxonomy combined with molecular systematics. Two new species of Gomphidius (G. borealis and G. pseudoflavipes) are described, one from Eastern Siberia and a second from rarely collected habitats in the Western United States. One taxon has the longest spores reported for the genus and the second species appears to be associated with a Siberian larch.

Crepidotus thermophilus comb. nov., a reassessment of Melanomphalia thermophila, a rarely collected tropical agaric.

Melanomphalia thermophila (Sing.) Sing. is a rarely collected agaric previously known only from Florida and Brazil. This taxon was originally described as a species of Tubaria and much of Singer's rationale for placing Tubaria within the Crepidotaceae (Imai) Sing. was based on anatomical similarities between T. thermophila and Crepidotus (Fr.) Staude. In later works, T. thermophila was transferred to Melanomphalia M.P. Christ., again forming the basis upon which Singer placed Melanomphalia within the Crepidotaceae. Based on examination of newly collected specimens from Puerto Rico and Panama, type studies, and nuclear large subunit rDNA analysis, we conclude that this taxon is, in fact, a centrally stipitate Crepidotus. Melanomphalia thermophila is transferred to Crepidotus, fully described and illustrated.