M. Catherine Aime

Ectomycorrhizal fungal diversity and community structure on three co-occurring leguminous canopy tree species in a Neotropical rainforest

• The ectomycorrhizal (ECM) symbiosis was historically considered restricted to the temperate zones, but recent studies have shown the importance of this symbiosis across the tropics. We examined ECM fungal diversity, host plant phylogeny and ECM host preferences in a rainforest dominated by the leguminous host plants Dicymbe corymbosa, Dicymbe altsonii and Aldina insignis. • Ectomycorrhizal fungi were identified by internal transcribed spacer rDNA sequencing and host species were verified with chloroplast trnL sequencing. To test whether Dicymbe and Aldina represent independent gains of the ECM symbiosis, we constructed a Fabaceae phylogeny using MatK and trnL. We identified four independent ECM lineages within the Fabaceae. • We detected a diverse community of 118 ECM species dominated by the /clavulina, /russula-lactarius, /boletus, and /tomentella-thelephora lineages. Ectomycorrhizal species in Agaricales, Atheliales and Polyporales may represent previously unrecognized tropical-endemic ECM lineages. Previous studies suggested that ECM fungi did not diversify in the tropics, but the /clavulina lineage appears to have a center of diversity in tropical South America. • Dicymbe and Aldina represent independent gains of the ECM symbiosis in Fabaceae but their fungal symbionts showed no host preferences. Spatial factors are more important than hosts in structuring the ECM fungal community in this ecosystem.

The genome of the xerotolerant mold Wallemia sebi reveals adaptations to osmotic stress and suggests cryptic sexual reproduction

Wallemia (Wallemiales, Wallemiomycetes) is a genus of xerophilic Fungi of uncertain phylogenetic position within Basidiomycota. Most commonly found as food contaminants, species of Wallemia have also been isolated from hypersaline environments. The ability to tolerate environments with reduced water activity is rare in Basidiomycota. We sequenced the genome of W. sebi in order to understand its adaptations for surviving in osmotically challenging environments, and we performed phylogenomic and ultrastructural analyses to address its systematic placement and reproductive biology. W. sebi has a compact genome (9.8 Mb), with few repeats and the largest fraction of genes with functional domains compared with other Basidiomycota. We applied several approaches to searching for osmotic stress-related proteins. In silico analyses identified 93 putative osmotic stress proteins; homology searches showed the HOG (High Osmolarity Glycerol) pathway to be mostly conserved. Despite the seemingly reduced genome, several gene family expansions and a high number of transporters (549) were found that also provide clues to the ability of W. sebi to colonize harsh environments. Phylogenetic analyses of a 71-protein dataset support the position of Wallemia as the earliest diverging lineage of Agaricomycotina, which is confirmed by septal pore ultrastructure that shows the septal pore apparatus as a variant of the Tremella-type. Mating type gene homologs were identified although we found no evidence of meiosis during conidiogenesis, suggesting there may be aspects of the life cycle of W. sebi that remain cryptic.

Phylogenetic relationships of sugarcane rust fungi

The phylogenetic positions of Puccinia spp. infecting sugarcane (a complex hybrid of Saccharum spp.) were determined using 38 newly generated rust sequences and 26 sequences from GenBank. Rust specimens on sugarcane were collected from 164 locations in 23 countries and identified based on light microscopy. The morphology for all samples matched that of Puccinia kuehnii or P. melanocephala, the orange and brown rust pathogens of sugarcane, respectively. Nuclear ribosomal DNA sequences (rDNA) including portions of the 5.8S rDNA, the complete internal transcribed spacer 2 (ITS2) and 5′ region of the large subunit (nLSU) rDNA were obtained for each species along with 36 additional rust taxa. Despite a shared host, the two Puccinia spp. on sugarcane are not closely related within the Pucciniales. Phylogenetic analyses place P. melanocephala most closely to P. miscanthi, P. nakanishikii, and P. rufipes infecting Miscanthus sinensis, Cymbopogon citratus, and Imperata cylindrica, respectively. Puccinia kuehnii is basal to a clade of Poaceae-infecting rusts including P. agrophila, P. polysora, P. substriata, and Uromyces setariae-italicae infecting Schizachyrium spp., Zea mays, Digitaria spp., and Urochloa mosambicensis, respectively. Light and scanning electron microscopy images highlight morphological differences distinguishing the two sugarcane-infecting species. This study confirms the separation of rust species infecting Poaceae from Cyperaceae- and Juncaceae-infecting rusts and also provides support for the presence of an additional group that includes P. kuehnii and other grass-infecting relatives.

New species of Inocybe from Dicymbe forests of Guyana

Four new species of Inocybe (Agaricales) with pleurocystidia and nodulose spores are recorded from a remote region of rain forest in Guyana, in northeastern South America. All four species of Inocybe occur in association with the arborescent legume genus, Dicymbe (Caesalpiniaceae, tribe Amherstieae). This constitutes the first report of a legume host genus with Inocybe in the neotropics. The new species are I. ayangannae, I. epidendron, I. lilacinosquamosa and I. pulchella. A dichotomous key, morphological descriptions, illustrations, taxonomic commentary, and a discussion of Inocybe in the tropics, are provided.

Molecular and pathogenic variation within Melampsora on Salix in western North America reveals numerous cryptic species.

In North America Melampsora rusts that parasitize willows (Salix species) have never been adequately studied and mostly have been referred to a collective species, Melampsora epitea (Kunze & Schm.) Thüm, of European origin. Even taxa that are nominally distinct from M. epitea, such as M. abieti-caprearum and M. paradoxa, currently are considered to be “races” of M. epitea. Within the range of our field surveys and collections in the Pacific Northwest and the Southwest only two species of Melampsora thus were expected: M. epitea (including its races) and M. ribesii-purpureae. In this study of Melampsora on 19 species of Salix in the western United States 14 phylogenetic species, or phylotypes, were apparent from nuclear rDNA sequencing of 140 collections or isolates. Our collections of the races of M. epitea, M. abieti-caprearum and M. epitea f. sp. tsugae belonged to one phylotype, termed lineage ‘N’. Assuming that M. ribesii-purpureae represents one other phylotype, 12 phylotypes still are unaccounted for by current taxonomy. Moreover Eurasian M. ribesii-purpureae was not closely related to any of the phylotypes reported here. Even more problematic was the resistance of Eurasian species of Salix, including the type host of M. epitea, S. alba, to North American Melampsora, including phylotype ‘N’, in both the field and in inoculation experiments. These results suggest the need for the description of many new species of Melampsora on Salix in western North America. Additional analyses presented here might guide further research in this direction.

Studies in neotropical polypores 15: new and interesting species from Guyana.

During fieldwork in Guyana several unusual and distinctive taxa of polypores were collected, three of which are described here as new. The first of these, Amauroderma coltricioides is the first species known in the Ganodermataceae with smooth basidiospores. Coltricia verrucata and Coltriciella navispora also are described as new, and a key to the neotropical species of Coltricia is provided. Finally, a checklist of 73 poroid fungi from Guyana is given, of which 29 are new records for the country.

New species and distribution records of Clavulina (Cantharellales, Basidiomycota) from the Guiana Shield

Two new species of Clavulina Schroet. (Clavulinaceae, Cantharellales, Basidiomycota) and new distribution records for Clavulina amazonensis Corner and Clavulina sprucei (Berk.) Corner are described from the Pakaraima Mountains of Guyana, in the central Guiana Shield region. These fungi occur in rainforests dominated by ectomycorrhizal (ECM) trees of the leguminous genus Dicymbe (Fabaceae subfam. Caesalpinioideae). Macromorphological, micromorphological and habitat data are provided for each species. Nuclear ribosomal DNA sequences of the internal transcribed spacer region and 28S subunit were obtained for new species and from representative collections of C. amazonensis and C. sprucei. The two new species, Clavulina kunmudlutsa sp. nov. and Clavulina tepurumenga sp. nov., constitute important edible fungi for the Patamona Amerindians. Our specimens of C. sprucei represent the first reports of the species since 1853 as well as a range extension of nearly 1500 km, while sequence data from basidiomata as well as ECM roots suggest that this taxon consists of a cryptic species complex.

New Clavulina species from the Pakaraima Mountains of Guyana

Five new species of Clavulina (Clavulinaceae, Cantharellales, Basidiomycota) are described from the Pakaraima Mountains of Guyana, occurring in rain forests dominated by the ectomycorrhizal tree Dicymbe corymbosa (Caesalpiniaceae). These clavarioid fungi have simple (i.e., unbranching) basidiomata, which is a relatively uncommon phenotypic feature for the genus Clavulina. Macromorphological, micromorphological, and habitat data are provided for each taxon, and nuclear ribosomal DNA sequences of the 28S subunit and internal transcribed spacer region were obtained for each holotype collection.

A new lineage in Pucciniomycotina: class Tritirachiomycetes, order Tritirachiales, family Tritirachiaceae

Based on multiple gene analyses (nuclear large subunit, nuclear small subunit, internal transcribed spacer region including the 5.8 s subunit rDNA, and translation elongation factor 1α) and septal pore ultrastructure we describe a new lineage of Pucciniomycotina consisting of a new class, Tritirachiomycetes, new order, Tritirachiales, and new family, Tritirachiaceae. Tritirachium dependens, T. oryzae, T. roseum (reintroduced), T. cinnamomeum and two unidentified species are recognized. Phylogenetic analyses do not support existing morphological circumscription of some species, and the available evidence suggests that morphological evaluation alone is not adequate for species identification.

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.