Unveiling Species Diversity Within Early-Diverging Fungi from China VI: Four Absidia sp. nov. (Mucorales) in Guizhou and Hainan

Abstract

Absidia is the most species-rich genus within the family Cunninghamellaceae, with its members commonly isolated from diverse substrates, particularly rhizosphere soil. In this study, four novel Absidia species, A. irregularis sp. nov., A. multiformis sp. nov., A. ovoidospora sp. nov., and A. verticilliformis sp. nov., were discovered from soil samples collected in southern and southwestern China, using integrated morphological and molecular analyses. Phylogenetic analyses based on concatenated ITS, SSU, LSU, Act, and TEF1α sequence data reconstructed trees that strongly supported the monophyly of each of these four new taxa. Key diagnostic features include A. irregularis (closely related to A. oblongispora) exhibiting irregular colony morphology, A. multiformis (sister to A. heterospora) demonstrating polymorphic sporangiospores, A. ovoidospora (forming a clade with A. panacisoli and A. abundans) producing distinctive ovoid sporangiospores, and A. verticilliformis (next to A. edaphica) displaying verticillately branched sporangiophores. Each novel species is formally described with comprehensive documentation, including morphological descriptions, illustrations, Fungal Names registration identifiers, designated type specimens, etymological explanations, maximum growth temperatures, and taxonomic comparisons. This work constitutes the sixth instalment in a series investigating early-diverging fungal diversity in China aiming to enhance our understanding of the diversity of fungi in tropical and subtropical ecosystems in Asia. In this paper, the known species of Absidia are expanded to 71.

Keywords: Mucoromycota; molecular phylogeny; new species; soil-borne fungi; taxonomy.

Figure 1

The Bayesian phylogenetic tree of Absidia based on ITS-SSU-LSU-Act-TEF1α sequences, with Cunninghamella blakesleeana CBS 782.68 as outgroup. The maximum likelihood bootstrap value (MLBV) ≥ 75 and the Bayesian inference posterior probability (BIPP) ≥ 0.85 are shown at the first and second positions and separated by a slash “/” on relevant nodes. The ex-types or ex-holotypes are in bold and marked with an asterisk “*”, and strains involved in this study are in red. Branches shortened to fit the page are represented by double slashes “//” and folds “×”. The scale at the bottom centre indicates 0.2 substitutions per site.

Figure 2

Absidia irregularis ex-holotype CGMCC 3.27812. (a,b) Colonies on PDA ((a) obverse; (b) reverse); (c,d) an unbranched sporangiophore with a sporangium; (e,f) columellae, collars, sporangiospores, and apophyses; (g) branched sporangiophores with sporangia; (h) branched sporangiophores with columellae, collars, sporangia, and apophyses; (i,j) rhizoids; (k) sporangiospores; bars: (c–k) 10 μm.

Figure 3

Absidia multiformis ex-holotype CGMCC 3.27807. (a,b) Colonies on PDA ((a) obverse; (b) reverse); (c,d) an unbranched sporangiophore with a sporangium; (e,f) columellae, collars, sporangiospores, and apophyses; (g) branched sporangiophores with columellae, collars, sporangium, and apophyses; (h,i) rhizoids; (j,k) sporangiospores; (l,m) zygospores; bars: (c–m) 10 μm.

Figure 4

Absidia ovoidospora ex-holotype CGMCC 3.27811. (a,b) Colonies on PDA ((a) obverse; (b) reverse); (c–e) an unbranched sporangiophore with a sporangium; (f) columellae, collars, sporangiospores, and apophyses; (g) unbranched sporangiophores with swelling and sporangium; (h) branched sporangiophores with columellae, collars, and apophyses; (i) branched sporangiophores with sporangia; (j) rhizoids; (k–m) giant cells; (n) sporangiospores; bars: (c–n) 10 μm.

Figure 5

Absidia verticilliformis ex-holotype CGMCC 3.27810. (a,b) Colonies on PDA ((a) obverse; (b) reverse); (c–e) an unbranched sporangiophore with a sporangium; (f) columellae, collars, sporangiospores, and apophyses; (g,h) branched sporangiophores with columellae, collars, sporangiospores, and apophyses; (i,j) rhizoids; (k) sporangiospores; bars: (c–k) 10 μm.