Assessment of yeasts in tropical peat swamp forests in Thailand

Despite the abundance of yeasts in peatland, only a few studies on peatland yeasts have been reported and, further, most of those studies were carried out in boreal regions. In response, this study assesses yeast communities in tropical peat swamp forests (PSFs). Peat soils or soils from a primary or natural PSF were collected in Thailand at Khanthuli PSF (PKT), while those from secondary or disturbed PSFs were collected from Khanthuli (SKT) and Khuankreng PSFs (SKK). Clone libraries of each sample were separately constructed using PCR products of the D1/D2 domains of the large subunit ribosomal DNA. Most of the yeast operational taxonomic units (OTUs) detected in Khanthuli PSF, both PKT and SKT, belonged to the phylum Ascomycota. Meanwhile, most of the yeast OTUs in SKK belonged to Basidiomycota. Each PSF area exhibited a specific yeast community. Only a few OTUs were shared between the different areas. The dominant yeast species in PKT and SKT was Galactomyces candidus, whereas in SKK, it was Solicoccozyma keelungensis. Saccharomyces cerevisiae was the only common species in each area. In addition, many more potential new yeast taxa are still undiscovered in the peatlands. The canonical correspondence analysis (CCA) showed that the abundance of G. candidus was related to sites with higher nitrogen concentrations and higher pH, while the abundance of So. Keelungensis was related to a combination of pH and electrical conductivity rather than total potassium contents. These results suggest that yeast communities in primary and secondary PSFs were different, which may be due to both biotic and abiotic factors.