Habitat-associated variation in morphology, cytology, and metabolite profiles of Pleurozium schreberi gametophytes

Pleurozium schreberi is one of the most abundant moss species in the Northern Hemisphere, valued as a bioindicator and a promising model for studying phenotypic plasticity. However, its habitat-associated variability among contrasting phytocoenoses remains poorly characterised. This study investigated gametophytes originating from five distinct phytocoenoses, heath, forest duct, young pine, mature pine, and mixed forest, using an integrative framework combining morphological, cytological, and metabolomic analyses. The results showed that reduced illuminance in pine forests was associated with higher soil organic carbon content and with increased frequencies of cells exhibiting nuclear DNA endoreplication up to the 4 C level. The largest leaf and cell sizes were observed in mature pine forest gametophytes, whereas mixed forest gametophytes exhibited intermediate dimensions, elongated chloroplasts, and high cell viability. Leaf cell walls from forest duct and young pine populations contained the highest levels of callose and cellulose. Principal Component Analysis (PCA) distinguished three habitat-associated population groups (heath/forest duct, young/mature pine forests, and mixed forests), while Spearman correlation analysis revealed positive associations of soil organic carbon content and temperature with growth-related traits and negative associations of pH and illuminance. Overall, these findings reveal clear habitat-associated variation among P. schreberi populations and demonstrate the usefulness of integrative multi-level analyses for investigating bryophyte variability and potential ecotypic differentiation.