High diversity and morphological convergence among melanised fungi from rock formations in the Central Mountain System of Spain

Abstract

Melanised fungi were isolated from rock surfaces in the Central Mountain System of Spain. Two hundred sixty six isolates were recovered from four geologically and topographically distinct sites. Microsatellite-primed PCR techniques were used to group isolates into genotypes assumed to represent species. One hundred and sixty three genotypes were characterised from the four sites. Only five genotypes were common to two or more sites. Morphological and molecular data were used to characterise and identify representative strains, but morphology rarely provided a definitive identification due to the scarce differentiation of the fungal structures or the apparent novelty of the isolates. Vegetative states of fungi prevailed in culture and in many cases could not be reliably distinguished without sequence data. Morphological characters that were widespread among the isolates included scarce micronematous conidial states, endoconidia, mycelia with dark olive-green or black hyphae, and mycelia with torulose, isodiametric or moniliform hyphae whose cells develop one or more transverse and/or oblique septa. In many of the strains, mature hyphae disarticulated, suggesting asexual reproduction by a thallic micronematous conidiogenesis or by simple fragmentation. Sequencing of the internal transcribed spacers (ITS1, ITS2) and 5.8S rDNA gene were employed to investigate the phylogenetic affinities of the isolates. According to ITS sequence alignments, the majority of the isolates could be grouped among four main orders of Pezizomycotina: Pleosporales, Dothideales, Capnodiales, and Chaetothyriales. Ubiquitous known soil and epiphytic fungi species were generally absent from the rock surfaces. In part, the mycota of the rock surfaces shared similar elements with melanised fungi from plant surfaces and fungi described from rock formations in Europe and Antarctica. The possibility that some of the fungi were lichen mycobionts or lichen parasites could not be ruled out.

Keywords: Capnodiales; Chaetothyriales; Dothideomycetes; biodiversity; black fungi; extremotolerance.

Fig. 1

General view of La Cabrera study site.

Fig. 2

Isolation frequencies of 162 different fungal genotypes isolated from stone. Genotypes were established based on a grouping by microsatellite-primed PCR products.

Fig. 3

Phylogram of the neighbour-joining tree obtained from melanised rock surface isolates and selected reference strains sequences of the ITS1-5.8S-ITS2 ribosomal region. Statistical support (1 000 bootstrap replicates) values of indicated at branch points of the main branches.

Fig. 4

Partial phylogram of the neighbour-joining tree obtained from melanised rock surface isolates and reference strains sequences of the ITS1-5.8S-ITS2 ribosomal region (Fig. 3). Branches corresponding to the Dothideales clade, ‘Coniosporium apollinis’ clade, ‘black yeasts’ group, and ‘Cryomyces’ clade.

Fig. 5

Partial phylogram of the neighbour-joining tree obtained from melanised rock surface isolates and reference strains sequences of the ITS1-5.8S-ITS2 ribosomal region (Fig. 3). Branches corresponding to the Chaetothyriales, Eurotiales, and Verrucariales clades.

Fig. 6

Partial phylogram of the neighbour-joining tree obtained from melanised rock surface isolates and reference strains sequences of the ITS1-5.8S-ITS2 ribosomal region (Fig. 3). Branches corresponding to the Mycosphaerellaceae, Venturiaceae, and Pleosporales clades.