Jun-Liang Zhou

Towards standardizing taxonomic ranks using divergence times – a case study for reconstruction of the Agaricus taxonomic system

The recognition of taxonomic ranks in the Linnean classification system is largely arbitrary. Some authors have proposed the use of divergence time as a universally standardized criterion. Agaricus (Agaricaceae, Agaricales) is a mushroom genus that contains many species of high commercial value. Recent studies using ITS sequence data discovered 11 new phylogenetic lineages within the genus, however their taxonomic ranks were uncertain due to the lack of criteria to define them within traditional taxonomy. In this study, we analyzed ITS sequence data from 745 collections (nearly 600 being newly generated) including 86 from type specimens of previously recognized subgenera and sections. Many monophyletic groups were recognized, but most basal relationships were unresolved. One hundred and fourteen representatives of the identified ITS clades were selected in order to produce a multi-gene phylogeny based on combined LSU, tef-1α, and rpb2 sequence data. Divergence times within the multi-gene phylogeny were estimated using BEAST v1.8. Based on phylogenetic relationships and with respect to morphology, we propose a revised taxonomic system for Agaricus that considers divergence time as a standardized criterion for establishing taxonomic ranks. We propose to segregate Agaricus into five subgenera and 20 sections. Subgenus Pseudochitonia is substantially emended; circumscription of the subgenera Agaricus and Flavoagaricus is restricted to taxa of sections Agaricus and Arvenses, respectively; and two new subgenera (Minores and Spissicaules) are introduced. Within Pseudochitonia, sections Bivelares, Brunneopicti, Chitonioides, Nigrobrunnescentes, Sanguinolenti and Xanthodermatei are maintained, but the latter two are reduced because we raise subsection Bohusia to sectional rank and a clade within section Xanthodermatei is formally introduced as section Hondenses; and sections Rubricosi, Crassispori, Flocculenti, and Amoeni are introduced. Section Laeticolores is placed in the subgenus Minores and sections Rarolentes and Subrutilescentes are placed in the subgenus Spissicaules. Twenty-two new species belonging to various sections are described. This work exemplifies that ITS data, while useful at lower taxonomic levels (i.e., detection of species and species groups), are of limited value for inferring deeper phylogenetic relationships. Finally, we suggest that the establishment of a standardized taxonomic system based on divergence times could result in a more objective, and biologically more meaningful, taxonomic ranking of fungi.

Taxonomy and Phylogeny of Polyporus Group Melanopus (Polyporales, Basidiomycota) from China

Melanopus is a morphological group of Polyporus which contains species with a black cuticle on the stipe. In this article, taxonomic and phylogenetic studies on Melanopus group were carried out on the basis of morphological characters and phylogenetic evidence of DNA sequences of multiple loci including the internal transcribed spacer (ITS) regions, the large subunit nuclear ribosomal RNA gene (nLSU), the small subunit nuclear ribosomal RNA gene (nSSU), the small subunit mitochondrial rRNA gene sequences (mtSSU), the translation elongation factor 1-α gene (EF1-α), the largest subunit of RNA polymerase II (RPB1), the second largest subunit of RNA polymerase II (RPB2), and β-tubulin gene sequences (β-tubulin). The phylogenetic result confirmed that the previously so-called Melanopus group is not a monophyletic assemblage, and species in this group distribute into two distinct clades: the Picipes clade and the Squamosus clade. Four new species of Picipes are described, and nine new combinations are proposed. A key to species of Picipes is provided.

Tropic origins, a dispersal model for saprotrophic mushrooms in Agaricus section Minores with descriptions of sixteen new species.

Agaricus section Minores contains the richest species diversity within the genus. Its Phylogeny is firstly presented by a Maximum Likelihood tree generated through DNA sequences from four gene regions of 91 species. Furthermore, a molecular dating analysis is conducted used those sequences, and it provided the divergence times of the clades within section Minores. Study showed section Minores has a tropical origin. Four main dispersal routes are proposed: (1) species from South Asia migrated through the Tibetan Plateau and reached Europe ca. 9–13 Ma; (2) species from out of South Asia dispersed to Europe in the earlier time of ca. 22 Ma; (3) species from South Asia dispersed through North Asia to Alaska, and reached West America around ca. 9 Ma; and (4) species from South Asia dispersed south and reached Oceania by at least three invading events about ca. 9, 12 and 16–18 Ma respectively. Those routes excepting the second route coincide with those of ectomycorrhizal mushrooms. To know whether the second route existed in the saprotrophic mushrooms requires further studies, and the fourth route may explain why the secotioid species occurring in Australia are morphologically similar but cluster in different phylogenetic clades. This study also demonstrates a great biodiversity of A. section Minores in China. Sixteen new species and three new records are introduced from China with morphological descriptions, illustrations, color photographs and phylogenetic analyses.

Two new species of Fomitiporia (Hymenochaetales, Basidiomycota) from Tibet, southwest China.

Two new species of Fomitiporia growing on Hippophae trees, F. norbulingka and F. subhippophaëicola, are described from southwest China based on morphological characters and phylogenetic analysis. Fomitiporia norbulingka is characterized by pileate basidiomata, mostly angular pores (6–9 per mm), slightly thick-walled generative hyphae, subglobose to globose basidiospores (6.5–7 × 5.5–7 μm), and absence of cystidioles. Fomitiporia subhippophaëicola is diagnostic by effused-reflexed to pileate basidiomata, angular pores (8–10 per mm), thick-walled generative hyphae, subglobose to obovoid basidiospores (6–8 × 5.5–7 μm), and presence of ventricose to fusoid cystidioles. Phylogenetic analysis inferred from combined sequences including the nuc rDNA ITS1-5.8-ITS2 region, 28S rDNA D1-D2 domains, partial sequences of translation elongation factor 1-α, and RNA polymerase II second largest subunits genes indicated that F. norbulingka and F. subhippophaëicola represent two new lineages which group together with F. hippophaëicola.

Phylogeny and taxonomy of Favolus (Basidiomycota)

ABSTRACT Favolus is a natural genus that is closely related to Polyporus. A taxonomic study of Favolus was carried out based on morphological characteristics and phylogenetic analysis of the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2 = ITS) and 18S and 28S genes of the nuc rDNA, translation elongation factor 1-α gene (TEF1-α), the mt 16S rDNA gene (mt rrnS), β-tubulin gene (TBB1), and the RNA polymerase II largest subunit (RPB1) and second largest subunit (RPB2) genes. Fourteen specimens collected from subtropical to tropical regions in China were shown to be different from existing Favolus species. They are described and illustrated here as four new species, namely, Favolus niveus, F. septatus, F. pseudoemerici, and F. subtropicus.

New species of Cystolepiota from China

ABSTRACT In this paper, a new species, Cystolepiota pseudofumosifolia, is introduced. C. pseudofumosifolia is characterized by granulose or powdery pileus with an anatomic structure that is loosely globose, as well as ellipsoid cells in chains in the pileus covering the cheilocystidia. This new species is compared to the related and similar Cystolepiota species in morphology and molecular phylogeny based on Internal transcribed spacer sequences. Both types of data support our specimens as a new species in the genus Cystolepiota.