A multigene phylogeny toward a new phylogenetic classification of Leotiomycetes.

Fungi in the class Leotiomycetes are ecologically diverse, including mycorrhizas, endophytes of roots and leaves, plant pathogens, aquatic and aero-aquatic hyphomycetes, mammalian pathogens, and saprobes. These fungi are commonly detected in cultures from diseased tissue and from environmental DNA extracts. The identification of specimens from such character-poor samples increasingly relies on DNA sequencing. However, the current classification of Leotiomycetes is still largely based on morphologically defined taxa, especially at higher taxonomic levels. Consequently, the formal Leotiomycetes classification is frequently poorly congruent with the relationships suggested by DNA sequencing studies. Previous class-wide phylogenies of Leotiomycetes have been based on ribosomal DNA markers, with most of the published multi-gene studies being focussed on particular genera or families. In this paper we collate data available from specimens representing both sexual and asexual morphs from across the genetic breadth of the class, with a focus on generic type species, to present a phylogeny based on up to 15 concatenated genes across 279 specimens. Included in the dataset are genes that were extracted from 72 of the genomes available for the class, including 10 new genomes released with this study. To test the statistical support for the deepest branches in the phylogeny, an additional phylogeny based on 3156 genes from 51 selected genomes is also presented. To fill some of the taxonomic gaps in the 15-gene phylogeny, we further present an ITS gene tree, particularly targeting ex-type specimens of generic type species. A small number of novel taxa are proposed: Marthamycetales ord. nov., and Drepanopezizaceae and Mniaeciaceae fams. nov. The formal taxonomic changes are limited in part because of the ad hoc nature of taxon and specimen selection, based purely on the availability of data. The phylogeny constitutes a framework for enabling future taxonomically targeted studies using deliberate specimen selection. Such studies will ideally include designation of epitypes for the type species of those genera for which DNA is not able to be extracted from the original type specimen, and consideration of morphological characters whenever genetically defined clades are recognized as formal taxa within a classification.

Fungal biogeography. Global diversity and geography of soil fungi.

Fungi play major roles in ecosystem processes, but the determinants of fungal diversity and biogeographic patterns remain poorly understood. Using DNA metabarcoding data from hundreds of globally distributed soil samples, we demonstrate that fungal richness is decoupled from plant diversity. The plant-to-fungus richness ratio declines exponentially toward the poles. Climatic factors, followed by edaphic and spatial variables, constitute the best predictors of fungal richness and community composition at the global scale. Fungi show similar latitudinal diversity gradients to other organisms, with several notable exceptions. These findings advance our understanding of global fungal diversity patterns and permit integration of fungi into a general macroecological framework.

Ascomycetes associated with ectomycorrhizas: molecular diversity and ecology with particular reference to the Helotiales.

Mycorrhizosphere microbes enhance functioning of the plant-soil interface, but little is known of their ecology. This study aims to characterize the ascomycete communities associated with ectomycorrhizas in two Tasmanian wet sclerophyll forests. We hypothesize that both the phyto- and mycobiont, mantle type, soil microbiotope and geographical distance affect the diversity and occurrence of the associated ascomycetes. Using the culture-independent rDNA sequence analysis, we demonstrate a high diversity of these fungi on different hosts and habitats. Plant host has the strongest effect on the occurrence of the dominant species and community composition of ectomycorrhiza-associated fungi. Root endophytes, soil saprobes, myco-, phyto- and entomopathogens contribute to the ectomycorrhiza-associated ascomycete community. Taxonomically these Ascomycota mostly belong to the orders Helotiales, Hypocreales, Chaetothyriales and Sordariales. Members of Helotiales from both Tasmania and the Northern Hemisphere are phylogenetically closely related to root endophytes and ericoid mycorrhizal fungi, suggesting their strong ecological and evolutionary links. Ectomycorrhizal mycobionts from Australia and the Northern Hemisphere are taxonomically unrelated to each other and phylogenetically distant to other helotialean root-associated fungi, indicating independent evolution. The ubiquity and diversity of the secondary root-associated fungi should be considered in studies of mycorrhizal communities to avoid overestimating the richness of true symbionts.