Saturday, April 14

The “Big Ditch” project: Trans‐Atlantic mushroom disjunction tested using multiple taxonomic tools

Ron Petersen et al. — Sat, 14 Apr 2012 16:25:00 PDT

Written descriptions and illustrations by historical Euro-Scandinavian mycologists crossed the Atlantic to America, where they were matched to fungi of the New World. Doubts about the accuracy of name applications across the ocean have persisted, but molecular phylogenies now provide a new level of resolution. Our research targets fleshy fungi whose names originated in Europe, but which bear the same name and superficial form in eastern North America. Several examples can be identified in which DNA sequences reveal differences across the ocean, including saprophytic (Marasmius rotula; Baeospora myosura; Sparassis crispa) and ectomycorrhizal (Strobilomyces strobilaceus; Tricholoma populinum) fungi. In addition, it appears that genes for sexual compatibility and recognition are more highly conserved than the internally transcribed spacer (ITS), but morphological differences vary with the individual taxon. Implications of this research include the necessity for new names for heretofore cryptic taxa on both continents and resultant adjustment of biodiversity inventory reports.

A phylogenetic evaluation of the tribe Leucopaxilleae: polyphyly, the LPD grade, and novel taxa from the Southern Appalachians

Marisol Sanchez-Garcia et al. — Sat, 14 Apr 2012 16:25:00 PDT

The tribe Leucopaxilleae Singer comprises eight genera that have been placed at various taxonomic ranks. Phylogenetic analysis of a four-gene region supermatrix (nuclear rRNA regions, rpb2) shows the tribe to be highly polyphyletic, with genera distributed in the Tricholomatoid, Marasmioid, Hygrophoroid and Pluteoid clades. Leucopaxillus, Porpoloma and Dennisiomyces, occur in the Tricholomatoid clade. Dennisiomyces, primarily a neotropical genus, has not been previously considered part of the Leucopaxilleae. We present preliminary data that suggest Dennisiomyces is closely related to Leucopaxillus and Porpoloma forming the 'LPD' grade (or clade) from which the ectomycorrhizal (ECM) genus Tricholoma appears to be derived. These results also suggest that Leucopaxillus and Porpoloma are polyphyletic. Additionally, three unknown species that form a clade nested in the 'LPD' grade have been collected recently from the Southern Appalachians of the southeast United States. They are distinguished from other species in the grade by possession of distinct cheilocystidia and pleurocystidia, presence of clamp connections, and inamyloid smooth spores. At present, we are unable to ascribe any known genus to this apparent endemic group.

Hygrophoraceae of the Great Smoky Mountain National Park ‐ how many have misapplied European names?

D. Jean Lodge et al. — Sat, 14 Apr 2012 16:05:00 PDT

The family Hygrophoraceae includes the brightly colored mushrooms commonly known as the wax-caps. From 2004-2008, we documented 40 species and varieties in the Hygrophoraceae. Of these, half bear European names, but 16 of them differ from the European species based on morphology and/or DNA sequences. Thus, these Smokies taxa have misapplied European names and most will need new names. Three European species also bear misapplied American names. Among the correctly named European species found in the Smokies, Neohygrocybe ingrata has not previously been reported in North America, but previous collections of this species have probably been misidentified as Hygrocybe nitrata. Hygrocybe reidii collected in the Smokies represents the first record for the USA, but this species has previously been reported from North America in Québec, Canada. Previous American collections of H. reidii have been misidentified as H. cantharellus, H. coccinea or H. punicea. DNA sequences of collections from the Great Smoky Mountain National Park have played a critical role in delineating species as well as in revision of the family Hygrophoraceae.

Afternoon Break

University of Tennessee - Knoxville — Sat, 14 Apr 2012 14:50:00 PDT

Like a rock? Lack of sequence variation in clinical isolates of the dermatophyte Trichophyton rubrum

Michael T. Gajdeczka et al. — Sat, 14 Apr 2012 14:30:00 PDT

Trichophyton rubrum (Ascomycota) – the cause of athlete’s foot, ringworm and nail infections – is the most common dermatophyte affecting humans. Despite availability of an annotated genome, this microbe’s pathogenicity, epidemiology, and genetics remain poorly understood due to an inability to conduct genetic crosses, lack of adequate sampling, and apparent clonality. The only evidence of sexual mating in T. rubrum is indirect - a single genetic hybrid was formed between T. rubrum and Arthroderma simii, the teleomorph of a related species (T. mentagrophytes). Trichophyton rubrum lacks a known teleomorph, and although its genome contains mating type genes, only a single MAT allele (MAT1-1) is known. This study has three aims: (1) survey sequence variation in our 194 clinical samples using sequence-based and previously-developed variable number tandem repeat (VNTR) markers; (2) use paired-end Illumina sequencing to identify additional polymorphism within and among strains belonging to different VNTR types, and (3) search for evidence of (same-sex) mating using genetic and culture-based methods. First, we sequenced 7.5 kb of mainly non-coding regions located within 20 kb of the ABC1 and CAP59 genes in ten T. rubrum isolates collected over a span of ten years. These sequences revealed six singleton polymorphisms, which distinguished only half of the strains. We are now transitioning to VNTR genotyping and whole genome Illumina sequencing to characterize the diversity more completely. Lastly, in order to test for formation of ascomata (sexual structures), we will co-culture ten of our T. rubrum isolates and a T. tonsurans isolate (MAT1-2) in single, pair-wise and triple combinations on dermatophyte mating medium. Cultures with extensive hyphal coiling (indicative of early sexual development) will be dissected and examined for presence of ascomata or ascospores. Thus far, our results provide no evidence of sexual reproduction and re-confirm low sequence variation in T. rubrum clinical isolates.

Dispersal of fungal and slime mold spores by vertebrate and invertebrate vectors

Courtney M. Trimble et al. — Sat, 14 Apr 2012 13:50:00 PDT

Numerous animals, including both vertebrates and invertebrates, serve as vectors for the spores of fungi and slime molds in terrestrial ecosystems. This is particularly important for dictyostelids (cellular slime molds), since the spores in this group of organisms are encased in a mucilaginous matrix that dries out, essentially eliminating the possibility of the spores being dispersed by wind. The latter is thought to be the primary method of dispersal for the spores of myxomycetes (plasmodial slime molds) and most fungi, but the consistent presence of spores in fecal material and on the body surface of animals ranging from insects to salamanders, birds and mammals suggests that many different invertebrates and invertebrates play an important but as yet understudied role in at least short-distance dispersal. Some species of birds travel considerable distances over relatively short time periods, especially during the course of annual migration and it seems likely that they would be able to serve as vectors for long-distance dispersal. Some evidence that this happens for dictyostelids already exists, and circumstantial evidence appears to indicate that birds were responsible for creating advance centers of infection for the chestnut blight fungus when the latter spread rapidly throughout the eastern United States in the early part of the last century. Truffles and other fungi are sought out by mammals yet the link between animal mycophagy and dispersal in North America is still largely unknown.

Dispersal of ectomycorrhizal fungi by mammals and its implications for Pinaceae invasion: results from Isla Victoria, Argentina

Martin A. Nuñez et al. — Sat, 14 Apr 2012 13:30:00 PDT

Invasive pines in New Zealand and Argentina are not associated with native EM fungi to any great extent, and tend to form symbiosis with non-indigenous fungi. Establishment of Pinaceae in such locations requires the co-introduction of compatible ectomycorrhizal (EM) fungi. Dispersal vectors of compatible ectomycorrhizal fungi from established plantations into native forests include wind and mammals. This project aimed to determine which local mammals can act as vectors of the mycorrhizal fungi on Isla Victoria, Argentina. We used non-indigenous deer and wild boar feces collected on the island to inoculate Pinaceae in a greenhouse experiment. We found that both mammals are dispersing fungi compatible with Pinaceae. Approximately 15 percent of the seedlings growing with deer fecal pellets were colonized and 30 percent of the seedlings growing with wild boar feces were colonized by EM fungi. Rodents are also well known to disperse fungi but observational evidence (by trapping) confirms that rodents are rare in areas adjacent to plantations of non-indigenous trees, so their ecological role seems to be insignificant. Very few fungal species were able to disperse via animal feces, possibly owing to animal preferences and/or the differential ability EM species to germinate after being ingested. The hypogeous genus Rhizopogon was the most abundant genus found. Wild boar, a recent addition to the local fauna, seems to be a key agent dispersing the fungi, so they may contribute to promote the invasions of pine trees. These results show that dispersal of ectomycorrhizal fungi can have an important role controlling the invasion of associated plant species.

Bayesian inference of species diversification rates using DivBayes and SubT

Martin Ryberg — Sat, 14 Apr 2012 13:10:00 PDT

One of the major tasks of evolutionary biology is to explain the vast diversity of organisms. Although it is controversial on what basis to recognize species, species are a basic unit of diversity. However, different species recognition concepts tend to agree the further the speciation process has progressed. The diversity of species in a specific group depends on the age of the group and the rate at which it has diversified through time. Differences in diversity between groups may therefore depend on either different ages or different rates of net diversification (speciation minus extinction). In this talk I will present DivBayes and SubT, two programs using Bayesian statistics to estimate diversification rates. DivBayes uses species number and clade age for the estimation while SubT uses node depths in an ultrametric tree. SubT is also able to account for missing taxa in the estimation, a characteristic that may otherwise bias the estimate.

Lunch

University of Tennessee - Knoxville — Sat, 14 Apr 2012 11:55:00 PDT

Accelerated fungal evolution with metabolic gene clusters

Jason Slot et al. — Sat, 14 Apr 2012 11:35:00 PDT

Shifts in fundamental ecological niche and competitive strategies are apparent in many lineages of Ascomycete and Basidiomycete fungi. The recent explosion of fungal genome sequencing projects has enabled investigations of the molecular underpinnings of these shifts. Through comparative investigations of gene phylogenies and genomic clustering, we have documented several cases of metabolic gene clusters facilitating fungal evolutionary leaps, involving horizontal gene transfer, concerted pathway loss and metabolic rewiring. Polymorphic loci encoding alternative pathways as gene clusters may serve as reservoirs for metabolic diversity underlying the exceptional adaptability of fungal genomes.