| Abstract [eng] |
Oak stands are important forest ecosystems for Lithuania and Europe, with their distinctive character and particularly rich biodiversity, which must be studied in detail if they are to be conserved. The aim of the present study was to reveal and compare the taxonomic diversity of fungal spores in three Lithuanian pedunculate oak (Quercus robur L.) stands using a time gradient and metagenomic approach. Objectives: 1) to collect spore samples in Punia, Dūkštos and Šilinė oak stands (protected areas) using passive spore traps; 2) to perform metagenomic analysis of the collected samples, and to perform taxonomic classification of fungal spores on the basis of the obtained DNA sequences of the ITS region; 3) to compare the taxonomic diversity of fungal spores among the three geographically distant stands of pedunculate oak; 4) to determine the patterns of occurrence of the identified fungi in a time gradient and under the influence of changing meteorological conditions; 5) to assess the frequency of occurrence of fungal species listed in the Lithuanian Red Data Book (RDB), invasive and organisms considered as quarantine species in the EU. Five spore traps were installed in each oak stand and inspected between August and September 2022; a total of 75 samples were collected over 5 weeks. After metagenomic analysis of the collected spores and bioinformatic analysis of the obtained data, the resulting DNA ITS region sequences were assigned to 1881 operational taxonomic units (OTUs), which were divided into 6 taxonomic phyla and 36 classes of fungi. Of the 1881 OTUs, 614 (32,6 %) could be identified to species level and 374 (19,9 %) to genus level. Of the 1881 OTUs, 999 taxa (53,1 %) were assigned to Ascomycota, 833 taxa (44,3 %) to Basidiomycota, and only 49 taxa (2,6 %) were assigned to Chytridiomycota, Mucoromycota, Olpidiomycota and Zoopagomycota. In terms of relative abundance of spores (DNA sequences), Basidiomycota fungi ranked first, with Ascomycota fungi second, while the other phyla showed negligible relative abundance of spores, which generally confirms the results obtained by other researchers in similar studies. Comparison of fungal communities in different stands showed that they did not differ significantly from each other in terms of species composition (both qualitatively and quantitatively), species richness, or evenness of species distribution, which may have been influenced by the relatively short distance (65-130 km) between the selected study sites. However, it was observed that the Punios stand was distinguished by the richness of fungal species (taxa) and the relative abundance of spores captured there. When analysing the data for the three stands as a whole, there was no significant correlation between the number of taxa and the average air temperature and relative humidity. Similarly, no significant correlation was observed when looking at the dependence of relative spore abundance on meteorological parameters. In the oak stands studied, saprotrophs dominated in terms of trophic (functional) groups, followed by pathogenic fungi (pathotrophs), while mycorrhizal and other symbiotrophic fungi accounted for a relatively low proportion of the spore mycobiota. The survey revealed two Basidiomycete species of the Lithuanian RDB – Fistulina hepatica and Xylobolus frustulatus. Two invasive species were also detected – the ash dieback pathogen Hymenoscyphus fraxineus and wheat pathogen Ustilago maydis. No fungal species considered as quarantine organisms (or recommended for control) in the European Union were found. It should be stressed that due to the very strict criteria applied for this work to determine the taxonomic level of a species, it is likely that some 'wanted' species remained unidentified. This is the first time that a study of this nature and scale has been carried out in Lithuanian oak stands; data on similar studies carried out in oak stands worldwide could not be found either. |
