Lichenicolous fungi are more specialized than their lichen hosts in primeval forest ecosystems, Białowieża Forest, northeast Poland

Shifts in Lichen Species and Functional Diversity in a Primeval Forest Ecosystem as a Response to Environmental Changes

Research highlights: shifts in the composition and functional diversity of lichen biota reflect changes in the environment caused by climate warming and eutrophication. Background and objectives: studies on lichen functional diversity and refinement in the functional traits of lichen biota under the pressure of changing environmental factors are currently of great scientific interest. The obtained results are interpreted in relation to specific habitat properties and their modifications due to the potential effects of climate change and atmospheric pollution. The aim of the work was to investigate changes in lichen species composition and functional diversity, as well as to identify factors responsible for them at different forest ecosystem scales. Materials and Methods: we identified factors responsible for changes in lichen biota in a unique Białowieża Forest ecosystem by analyzing shifts in species optima and functional diversity at the forest community, tree phorophyte, and substrate levels. We examined individual lichen species’ responses and temporal shifts in the species composition for each historical and resampled dataset using a community-weighted means of functional lichen traits and Wirth ecological indicator values. Results: the most evident change took place at the level of individual species, which shifted their realized optima: 25 species demonstrated a shift to co-occur with lichens of higher nitrogen demands, 15 demonstrated higher light demands, 14 demonstrated higher temperature preferences, and six demonstrated lower moisture preferences. At the level of forest communities, biota shifted towards the higher proportion of nitrogen-demanding and the lower proportion of moisture-demanding species. At the level of phorophyte species, biota changed towards an increased proportion of lichens of higher temperature preferences. For the substrate level, no directional shifts in lichen species composition were found. Conclusions: climate change has influenced lichen biota in Białowieża Forest, but the main driver of lichen species composition was found to be eutrophication. We suppose that other overlapping factors may contribute to biota shifts, e.g., the extinction and expansion of phorophyte tree species.

Composition and Specialization of the Lichen Functional Traits in a Primeval Forest—Does Ecosystem Organization Level Matter?

Current trends emphasize the importance of the examination of the functional composition of lichens, which may provide information on the species realized niche diversity and community assembly processes, thus enabling one to understand the specific adaptations of lichens and their interaction with the environment. We analyzed the distribution and specialization of diverse morphological, anatomical and chemical (lichen secondary metabolites) traits in lichen communities in a close-to-natural forest of lowland Europe. We considered these traits in relation to three levels of forest ecosystem organization: forest communities, phorophyte species and substrates, in order to recognize the specialization of functional traits to different levels of the forest complexity. Traits related to the sexual reproduction of mycobionts (i.e., ascomata types: lecanoroid apothecia, lecideoid apothecia, arthonioid apothecia, lirellate apothecia, stalked apothecia and perithecia) and asexual reproduction of mycobionts (pycnidia, hyphophores and sporodochia) demonstrated the highest specialization to type of substrate, tree species and forest community. Thallus type (foliose, fruticose, crustose and leprose thalli), ascospore dark pigmentation and asexual reproduction by lichenized diaspores (soredia and isidia) revealed the lowest specialization to tree species and substrate, as well as to forest community. Results indicate that lichen functional trait assemblage distribution should not only be considered at the level of differences in the internal structure of the analyzed forest communities (e.g., higher number of diverse substrates or tree species) but also studied in relation to specific habitat conditions (insolation, moisture, temperature, eutrophication) that are characteristic of a particular forest community. Our work contributes to the understanding of the role of the forest structure in shaping lichen functional trait composition, as well as enhancing our knowledge on community assembly rules of lichen species.