Distinct intraspecific trait variations in two moss species: Insights from a latitudinal investigation across 66...

As a non-negligible component of functional trait diversity, intraspecific trait variation (ITV) represents a direct response of local populations to environmental change and significantly influences ecological processes such as species dispersal, community assembly, and ecosystem functioning. Although extensively studied in vascular plants, ITV remains underexplored in mosses, which possess fundamentally distinct evolutionary status, structures, and adaptive strategies. In this study, we sampled two common subtropical terricolous and saxicolous moss species (Hyophila propagulifera and Pogonatum inflexum) from 66 coastal islands (spanning a latitudinal range of 23.4-30.9°N) in southeastern China, measured their morphological and anatomical traits and water holding and retention capacities, identified the effects of latitude and environmental factors on each trait, and calculated the relative contributions. For both species, the trait with the highest variation was shoot mass, whereas the shapes of the stem transverse section, leaf, and leaf cells were relatively conserved. In H. propagulifera, stem size and internal transport capacity increased along a latitudinal gradient, however, the water holding and retention capacities were not associated with any of the studied environmental factors. In P. inflexum, lamella length was negatively correlated with precipitation, whereas no clear ITV patterns were observed in other traits, probably because of Polytrichaceae's unique characteristics and the more stable microclimates of soil substrates compared with rock. This work expands our understanding of the adaptive evolutionary strategies of poikilohydric plants and bridges knowledge gaps in their conservation from the perspective of functional adaptation. We suggest that future studies focus on the impacts of climatic events on mosses and combine functional traits with community structure surveys to accurately quantify their ecosystem functioning and services.