The role of phorophyte species and interspecific interactions in co-occurrence patterns of the primeval forest relict Dicranum viride

Bryophytes, particularly epiphytes, play a vital role in the nemoral forest ecosystems of the temperate climate zone, influencing microclimate, providing habitats, and contributing to biodiversity. Dicranum viride, a target moss species within the Natura 2000 network, is of significant conservation value. Its preservation is crucial for forest managers who strive to protect the naturalness and integrity of nemoral forest ecosystems. Understanding its habitat preferences, co-occurrence patterns, and interactions within co-created epiphytic communities is essential for effective conservation and a more comprehensive understanding of its biology. Our research examines the co-occurrence patterns of D. viride within epiphytic communities. Specifically, we focused on the influence of the phorophyte (host tree) species and interspecific interactions on the composition of co-occurring bryophytes. We conducted field surveys in eastern Poland to investigate the distribution of D. viride in several forest ecosystems located in five Natura 2000 sites. Each occurrence of the target moss was recorded along with forest type, phorophyte species, and co-occurring bryophyte taxa. The collected data were then used for network analyses, including pairwise co-occurrence interactions based on a probabilistic model of species co-occurrence. Dicranum viride occurred most frequently on the bark of Fagus sylvatica and Carpinus betulus, particuraly in Fagion sylvaticae and Carpinion betuli. Network analyses revealed that the composition of co-occurring taxa varied depending on phorophyte species, with interspecific interactions among bryophytes significantly influencing these differences. Our study highlights the significant role of D. viride as an umbrella species in European woodlands, emphasizing its prevalence in Fagion sylvaticae and Carpinion betuli forest types, and its affinity for Fagus sylvatica and Carpinus betulus as phorophyte species. Implementing zonal protection for D. viride should be considered a progressive step in sustainable forest management, ensuring the conservation of its habitats and contributing not only to the biodiversity of woodland ecosystems, but also to the preservation of the most valuable ones. By unravelling the complex relationships within epiphytic communities, especially those involving flagship species such as D. viride, our research emphasises the importance of considering both the presence of co-occurring taxa and the nature of their interactions in studies of co-created community dynamics.