Integrating morphology, phylogeny, substrate, and distribution: clarifying the major phylogenetic framework of Pluteus sect. Hispidoderma (Agaricales, Pluteaceae) and describing 18 species

Abstract

Pluteus is a genus of wood-rot fungi with considerable ecological importance in forest ecosystems. Within this genus, section Hispidoderma is distinctively characterized by a specific combination of pileipellis structures (trichoderm, hymeniderm, or trichohymeniderm) and non-metuloid hymenial cystidia, which together provide key morphological basis for section delimitation. In this study, we combined genetic data from three gene regions (large subunit ribosomal RNA [LSU], internal transcribed spacer [ITS], and translation elongation factor 1 - alpha [tef 1]) to construct the major phylogenetic framework of section Hispidoderma.

Our analysis revealed three primary clades (/ plautus clade, / leoninus clade, / umbrosus clade) and one lineage (/ pantherinus lineage). We subsequently identified several important morphological features and correlated them with phylogenetic relationships to reveal shared characteristics among species within each evolutionary clade. Building on this framework, we constructed phylogenetic trees using three datasets (ITS, tef 1 and a combined ITS + tef 1) to analyze the phylogenetic structure and species relationships within each clade and lineage.

By comprehensively integrating morphology, phylogenetic data, substrate preferences, and species distribution, we identified 18 species: nine new species (P. albivillus, P. baishanzuensis, P. costatus, P. hinnuleus, P. jilinensis, P. piceicola, P. spaniophyllus, P. tenuipileus, and P. ultraputripiceae), one new record for China (P. ussuriensis), seven previously known species (P. granularis, P. leoninus, P. longistriatus, P. umbrosus, P. umbrosoides, P. variabilicolor, and P. velutinus), and one species of uncertain taxonomic affinity (P. aff. semibulbosus).

This study provides detailed documentation, including line drawings and color photographs of the 18 identified species, along with phylogenetic analyses of their evolutionary relationships. Additionally, we present a thorough identification key for the 25 species of sect. Hispidoderma found in China.

By clarifying the delineation of clades and species boundaries within sect. Hispidoderma, this work significantly advances our understanding of the taxonomy of this ecologically important fungal group.