Unravelling the fungal darkness in a tropical cave: richness and the description of one new genus and six new species

Abstract

Caves are special environments that harbour an incredible diversity of life, including fungal species. Brazilian caves have been demonstrated to be biodiversity hotspots for known and unknown fungal species. We investigated the richness of culturable fungi in a tropical cave in Brazil by isolating these microorganisms from the sediment and air. The fungal abundance of colony-forming units (CFUs) was 3 178 in sediment and 526 in air. We used morphological features and phylogenetic analyses of actin (actA), calmodulin (cmdA), internal transcribed spacer regions and intervening 5.8S rRNA (ITS), large subunit (LSU) rDNA, RNA polymerase II second largest subunit (rpb2), translation elongation factor 1-alpha (tef1), and β-tubulin (tub2) genes to identify these isolates. Forty-one species belonging to 17 genera of Ascomycota and two of Basidiomycota were identified, and the genus Aspergillus was most commonly observed in the cave (13 taxa). Twenty-four species were found in sediment (16 exclusives) and 25 species were found in air (17 exclusives). In this study, we introduced a new genus (Pseudolecanicillium gen. nov.) in the family Cordycipitaceae and six new species (14 % of the total taxa identified) of fungal isolates obtained from sediment and air: Aspergillus lebretii sp. nov., Malbranchea cavernosa sp. nov., Pseudohumicola cecavii sp. nov., Pseudolecanicillium caatingaense sp. nov., Talaromyces cavernicola sp. nov., and Tritirachium brasiliense sp. nov. In addition, we built a checklist of the fungal taxa reported from Brazilian caves. Our results highlight the contribution of Brazilian caves to the estimation of national and global fungal diversity. Citation: Alves VCS, Lira RA, Lima JMS, Barbosa RN, Bento DM, Barbier E, Bernard E, Souza-Motta CM, Bezerra JDP (2022). Unravelling the fungal darkness in a tropical cave: richness and the description of one new genus and six new species. Fungal Systematics and Evolution 10: 139-167. doi: 10.3114/fuse.2022.10.06.

Keywords: Aspergillus; Caatinga dry forest; cave environment; fungal taxonomy; novel taxa.

Fig. 1.

A. The geographical location of the Abrigo do Letreiro cave in the Furna Feia National Park, Brazil. B. Cave sketch showing the sampling points (SP1, SP2 and SP3). The cave sketch was adapted from one drawn by the CECAV/ICMBio-MMA, Brazil.

Fig. 2.

Abrigo do Letreiro cave in the Furna Feia National Park, Brazil. A. Outside skylight view and the tree Erythrina velutina (Fabaceae). B. Inside skylight view and the tree E. velutina. C. Sampling point 2 and cave paintings with geometric tradition and symbolist style distributed along the walls and ceiling of the cave. D. A small colony of bats (Peropteryx macrotis) at the sampling point 1. E. Petri dishes used to sample airborne fungi at the sampling point 2. Photos were taken by D.M. Bento.

Fig. 3.

Bayesian phylogenetic tree using sequences of cmdA-tub2-rpb2 of species included in Aspergillus section Cremei. The new species described in this study (Aspergiilus lebretii) is highlighted in blue. Ex-type strains are in bold. Values for ML-BS ≥70 % and BPP ≥0.95 are included near nodes. The tree was rooted to Aspergillus glaucus NRRL 117.

Fig. 4.

Bayesian phylogenetic tree using sequences of ITS-LSU of species included in Malbranchea. The new species described in this study (Malbranchea cavernosa) is highlighted in blue. Ex-type strains are in bold. Values for ML-BS ≥70 % and BPP ≥0.95 are included near nodes. The tree was rooted to Arachnomyces jinanicus CGMCC3.14173.

Fig. 5.

Bayesian phylogenetic tree using sequences of ITS-rpb2-tub2 of species included in Humicola and Pseudohumicola. The new species described in this study (Pseudohumicola cecavii) is highlighted in blue. Ex-type strains are in bold. Values for ML-BS ≥70 % and BPP ≥0.95 are included near nodes. The tree was rooted to Chaetomium globosum CBS 160.62.

Fig. 6.

Bayesian phylogenetic tree using sequences of ITS-LSU-rpb2-tef1 of species included in the family Cordycipitaceae. The new genus and species described in this study (Pseudolecanicillium caatingaense) are highlighted in blue. Ex-type strains are in bold. Values for ML-BS ≥70 % and BPP ≥0.95 are included near nodes. The tree was rooted to Purpureocillium lilacinus CBS 284.36 and CBS 431.87.

Fig. 7.

Maximum likelihood tree using sequences of cmdA-tub2-rpb2 of species included in Talaromyces section Talaromyces. The new species described in this study (Talaromyces cavernicola) is highlighted in blue. Ex-type strains are in bold. Values for ML-BS ≥70 % and BPP ≥0.95 are included near nodes. The tree was rooted to Talaromyces trachyspermus CBS 373.48.

Fig. 8.

Maximum likelihood tree using sequences of ITS of species included in Tritirachium and related genera. The new species described in this study (Tritirachium brasiliense) is highlighted in blue. Ex-type strains are in bold. Values for ML-BS ≥70 % and BPP ≥0.95 are included near nodes. The tree was rooted to Sakaguchia dacryoidea CBS 6353 and Symmetrospora coprosmae CBS 7899.

Fig. 9.

Aspergillus lebretii URM 8451. A. Colonies from left to right (top row) MEA, CYA, CZ, YES, CYAS and OA; (bottom row) MEA, CYA, CZ, YES, CYAS reverse and CREA, after 7 d at 25 °C in the dark. B–G. Conidiophore and conidia. H. Conidia. I. Schematic line drawing of Aspergillus lebretii. Scale bars: B = 100 μm; C–E = 50 μm; F, G = 25 μm; H = 10 μm.

Fig. 10.

Malbranchea cavernosa URM 8445. A. Colonies on PDA, OA and SNA after 4 wk at 25 °C in the dark. B. Ascoma. C. Ascoma gymnothecium. D. Reticuloperidium terminated by spine-like projection. E, F. Appendages. G. Asci. H. Ascospores. I. Schematic line drawing of Malbranchea cavernosa. Scale bars: B = 300 μm; C, E, F = 50 μm; D, G, H = 10 μm.

Fig. 11.

Pseudohumicola cecavii URM 8444. A. Colonies from left to right (top row) PDA, MEA and OA; (bottom row) PDA reverse, MEA reverse and SNA after 7 d at 25 °C in the dark. B–G. Conidiophore, conidiogenous cells and conidia. H–J. Conidiophore, conidiogenous cells, conidia and chlamydospores. Scale bars = 10 μm.

Fig. 12.

Schematic line drawing of Pseudohumicola cecavii URM 8444.

Fig. 13.

Pseudolecanicillium caatingaense URM 8447. A. Colonies on PDA, OA and SNA after 2 wk at 25 °C in the dark. B, C. Conidiophores, conidiogenous cells and conidia. D–H. Details of conidiogenous cells and conidia. I. Conidia. Scale bars = 10 μm.

Fig. 14.

Schematic line drawing of Pseudolecanicillium caatingaense URM 8447.

Fig. 15.

Talaromyces cavernicola URM 8448. A. Colonies from left to right (top row) MEA, CYA, CZ, YES and OA; (bottom row) MEA, CYA, CZ, YES reverse and CREA after 7 d at 25 °C in the dark. B–F. Conidiophore and conidia. G. Conidia. H. Schematic line drawing of Talaromyces cavernicola. Scale bars: B = 100 μm; C–G = 10 μm.

Fig. 16.

Tritirachium brasiliense URM 8535. A. Colonies from left to right OA, PDA, CYA, YES and SNA after 7 d at 25 °C in the dark. B–F. Conidiophores, conidiogenous cells and conidia. G, H. Details of conidiogenous cells. I. Conidia. Scale bars: B–D = 100 μm; E–I = 10 μm.

Fig. 17.

Schematic line drawing of Tritirachium brasiliense URM 8535.